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Imaging of spindle cell lipoma
Clinical Radiology xxx (xxxx) xxx
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Imaging of spindle cell lipoma J.S. Jelinek a, *, A. Wu b, M. Wallace c, D. Kumar a, R.M. Henshaw c, M.J. Murphey d, A. Van Horn c, A.J. Aboulafia c a
Department of Radiology, MedStar Washington Hospital Center, 110 Irving Street, NW, Washington DC, 20010, USA Department of Internal Medicine, MedStar Franklin Square Medical Center, 9000 Franklin Square Drive, Baltimore, MD, 21237, USA c Department of Orthopedic Oncology, MedStar Franklin Square Medical Center, 9000 Franklin Square Drive, Baltimore, MD, 21237, USA d American Institute for Radiologic Pathology, 1100 Wayne Avenue, Silver Spring, MD, 20910, USA b
art icl e i nformat ion Article history: Received 6 June 2019 Accepted 26 November 2019
AIM: To review the evaluation, diagnosis, and treatment of spindle cell lipoma (SCL) with emphasis on the location of these tumours and the spectrum of magnetic resonance imaging (MRI) and computed tomography (CT) appearances. MATERIALS AND METHODS: The MRI and CT findings of 27 histopathologically proven SCLs were evaluated retrospectively. Imaging features evaluated included margins, percentage visible fat, MRI signal characteristics, oedema, and contrast enhancement patterns. RESULTS: Patient ages ranged from 18 to 80 years with an average age of 56.5 years. Men were affected twice as frequently as women (M¼18, F¼9). SCLs ranged in size from 2 to 10 cm, with an average greatest dimension of 5.5 cm. Five lesions (19%) contained no visible fat on CT or MRI, and the leading differential diagnosis of high-grade soft-tissue sarcoma diagnosis was suggested by referring surgeons. Five lesions (19%) had <50% fatty areas, nine lesions (52%) demonstrated >50% but <90% fat at MRI or CT. Only three of 25 lesions (12%) had an appearance of a typical lipoma on unenhanced MRI sequences. All SCLs that were imaged with contrast medium (n ¼ 18) demonstrated some degree of enhancement, with eight (44%) showing marked enhancement, four (22%) showing moderate, and six (33%) minimal enhancement. CONCLUSION: SCLs have considerably variable imaging appearances and may have minimal or no visible fat at MRI or CT. Imaging features may make it difficult to distinguish this benign tumour from a potentially higher-grade malignant tumour. Ó 2019 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Introduction Spindle cell lipoma (SCL), first reported in 1975 (1), is a rare, slow-growing, benign variant of lipoma. SCL accounts
for approximately 1.5% of biopsy-analysed lipomas1e4 and are composed of mature adipocytes, uniformly proliferated spindle cells embedded within a rope-like collagen fibres and mucoid stroma.1e6 SCL typically presents as a welldefined heterogeneous subcutaneous mass. It has been
* Guarantor and correspondent: J. S. Jelinek, Department of Radiology. MedStar Washington Hospital Center, 110 Irving Street, NW, Washington DC, 20010, NW, USA, Tel.: þ1 202 877 6088. E-mail address: [email protected] (J.S. Jelinek). https://doi.org/10.1016/j.crad.2019.11.020 0009-9260/Ó 2019 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Please cite this article as: Jelinek JS et al., Imaging of spindle cell lipoma, Clinical Radiology, https://doi.org/10.1016/j.crad.2019.11.020
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reported to occur most commonly in middle-aged men (10:1 male-to-female ratio) between 45 and 70 years (a mean of 54 years) with a predilection for the “shawl area” (shoulder, posterior neck, and upper back).1,2,5,6 In clinical practice, the present authors found the classic description of sex, age, and location SCL to be less accurate than reported previously. Unlike lipoma, SCL appearance at MRI is not characteristic, and is easily misdiagnosed as a softtissue sarcoma.7e10 Their uncharacteristic MRI imaging has been described in radiology journals,7e13 but the surgical practitioner must likewise be aware of the diagnostic challenges of this unusual entity. The wide spectrum of imaging appearances can be confused with lipomas, atypical lipomatous tumours (ALT), well-differentiated liposarcoma (WDLS), and high-grade soft-tissue sarcomas.13e15 MRI is nearly 100% accurate in the diagnosis of simple lipoma, and can further identify features suggestive of atypical lipomatous tumour. Pathologically, however, SCLs may show a significant amount of fat, minimal fat, or no fat (Figs 1e4). MRI reflects the gross morphology of the lesion, which often has potential for misdiagnosis.7,11 Although histological examination is the reference standard for diagnosis, clinical presentation and imaging may offer a more accurate preoperative assessment to assist the surgeon in choosing the preferred method of biopsy, resection, or observation. The purpose of the present study was to review the evaluation, diagnosis, and treatment of SCL with emphasis on the location of these tumours and the spectrum of MRI and CT appearances.
Figure 2 Cellular area of tumour showing spindle cells separated by dense collagen (haematoxylin and eosin staining, 200).
Materials and methods After institutional IRB review and approval, the clinical, surgery, pathology, and radiology databases were reviewed retrospectively for the diagnosis of SCL for the years 2006e2015. Inclusion criteria included a final histopathological diagnosis of SCL after tumour resection, and available clinical data and preoperative evaluation by MRI, CT, or
Figure 1 Admixture of mature fat and spindle cells (haematoxylin and eosin staining, 40).
Figure 3 Fat-free SCL (haematoxylin and eosin staining, 200).
Figure 4 SCL with extensive myxoid change (haematoxylin and eosin staining, 200).
Please cite this article as: Jelinek JS et al., Imaging of spindle cell lipoma, Clinical Radiology, https://doi.org/10.1016/j.crad.2019.11.020
J.S. Jelinek et al. / Clinical Radiology xxx (xxxx) xxx
both. MRI studies needed to have a minimum of two orthogonal planes and include typical T1-weighted and fatsuppressed T2-weighted or STIR (short T1 inversion recovery) sequences. CT studies were performed without intravenous contrast medium using a multidetector CT system. A total of 27 surgically resected and histopathologically proven SCLs that met inclusion criteria from two busy orthopaedic oncology practices were identified. A dedicated musculoskeletal radiologist and a fellowship-trained orthopaedic surgical oncologist reviewed the records and imaging of all cases independently. Evaluation included patient demographics, size, anatomical location, compartment location, and imaging features on MRI (n ¼ 25) and CT (n ¼ 7). Seven patients had both CT and MRI. Tumour location was assessed for the anatomical region of the body as well as the relationship to the subcutaneous (superficial) space above the fascia versus deep intramuscular or deep intermuscular compartments. Tumour size was measured in centimetres at its greatest dimensions. Imaging features evaluated included margins, percentage visible fat, CT attenuation, and MRI signal characteristics and enhancement pattern. Lesion margin was assessed as a well-defined capsule (rim of low-signal intensity tissue), defined without a capsule, or as poorly defined (no borders). The percentage of visible fat within the tumour was assessed subjectively based on the amount of fat (density on CT and iso-intensity to fat-on non-fatsaturated T1-weighted MRI images) within the entire lesion using the axial, sagittal, and coronal images. Fat content was scored as no fat, <50% fat, >50 but <90% fat and >90%. The degree of enhancement was assessed subjectively as none, minimal, moderate, or marked on the contrast-enhanced fat-saturated T1-weighted images as compared to the unenhanced T1-weighted images and the adjacent subcutaneous fat. Peripheral oedema was again subjective comparing high signal around the lesion on the fatsaturated T2-weighted or STIR sequences as compared to adjacent subcutaneous fat. The MRI signal intensity of the mass was assessed on both T1-and T2-weighted fatsuppressed or STIR sequences. Clinical follow-up for tumour recurrence was assessed by review of the clinical databases with a minimum of 3 years and a maximum of 11 years.
Results Patient ages ranged from 18 to 80 years with an average age of 56.5 years. Men were affected only twice as frequently as women (M¼18, F¼9). The most common locations included flank/paraspinal (24%), neck (20%), shoulder (16%), foot/ankle (12%), and other (28%). SCLs were observed most commonly in the subcutaneous fat (67%), followed by intermuscular (19%) and intramuscular (15%) intervals. SCLs ranged in size from 2 cm to a maximum dimension of 10 cm, with an average greatest dimension of 5.5 cm. Evaluation of tumour margins demonstrated that 11 (40%) were very well defined, 11 (40%) were relatively well defined, and five (19%) were poorly defined (Table 1).
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Analysis of visible fat content revealed five (19%) lesions contained no visible fat on CT or MRI. Six lesions (22%) of SCLs had 50% fat. Nine lesions (33%) had >50% but <90% fat at MRI or CT (Figs 5e7). Only three of 25 (12%) lesions were iso-intense to the adjacent subcutaneous fat on noncontrast MRI sequences, consistent with the overall appearance of lipoma. One of these did not show contrast and could not be discerned from lipoma. The other two had increased enhancement greater than adjacent subcutaneous fat. On MRI, 22 of 25 (88%) demonstrated varying degrees of hyperintensity on T2-weighted/STIR sequences. Peritumoural oedema was noted in nine of 25 (36%) cases of SCL on MRI, all of which were characterised as minimal. No cases of oedema were identified by CT. There were no tumours with moderate to marked peritumoural oedema. All SCLs evaluated with contrast-enhanced MRI studies (n ¼ 18) demonstrated enhancement (Figs 5e7). Eight lesions (44%) were characterised by marked enhancement, six lesions (33%) showed moderate enhancement, and four lesions (22%) demonstrated minimal enhancement. CT was performed without contrast medium and enhancement could not be assessed (Table 1). Clinically, all patients underwent complete en-bloc surgical resection with a marginal to wide surgical margin. There were no major surgical complications, and there have been no reported local recurrences.
Discussion Historically, the imaging of lipomas and liposarcomas has been oversimplified; tumours that were identical to subcutaneous fat on all MRI sequences were lipomas. Predominantly fatty tumours with areas of significant enhancement or high signal intensity on T2-weighted images likely represented ALT if located in the extremities or WDLS if in the retroperitoneum15e17; however, there are other benign fatty tumours that may have indeterminate imaging characteristics such as ALT and liposarcoma. Hibernomas18 are a well-known, albeit much rarer, entity, which can have similar imaging characteristics to either lipoma or liposarcoma.18,19 SCLs are being increasingly recognised for their wide spectrum of imaging appearances and are more common than hibernomas. SCL imaging appearances range from an appearance resembling that of a simple lipoma, To more cellular lesions with T2-weighted hyperintensity that may mimic ALT, to lesions with scant or absent fatty content, suggestive of a soft-tissue sarcoma.7e13 Classic teaching has described SCL as an entity almost exclusively seen in older men in a “shawl” distribution covering the posterior neck, midline of the upper back and medial shoulders.1,2 Furthermore, these were described as classically subcutaneous, superficial lesions. The present series demonstrated a 2:1 ratio of males-tofemales, which is much lower than the previously reported 10:1 ratio.1,2,9,13 There was a wide range of patient ages, which is different from most prior reports that describe 90% of SCLs as occurring in older men.1e5,9,12 Less than half of the present cases occurred in the subcutaneous
Please cite this article as: Jelinek JS et al., Imaging of spindle cell lipoma, Clinical Radiology, https://doi.org/10.1016/j.crad.2019.11.020
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Table 1 Spindle Cell Lipoma Case Data. Patient #
Age
Sex
Location
Location
Largest Size (cm)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 19 20 21 22 23 24 25 18 26 27
59 65 48 47 33 63 78 80 52 48 63 24 39 75 65 46 71 79 44 18 62 71 24 71 73 65 64
F F M M M M F M M F M F M M M F M F M M M M F M M F M
Subcutaneous Intramuscular Subcutaneous Intermuscular Subcutaneous Subcutaneous Subcutaneous Subcutaneous Intramuscular Subcutaneous Subcutaneous Subcutaneous Subcutaneous Subcutaneous Intermuscular Intramuscular Intermuscular Intermuscular Subcutaneous Intermuscular Subcutaneous Subcutaneous Subcutaneous Subcutaneous Subcutaneous Subcutaneous Intramuscular
Foot/Ankle Back/Paraspinal Knee Shoulder Shoulder Knee Foot/Ankle Back/Paraspinal Neck Arm Neck Back/Paraspinal Neck Neck Arm Back/Paraspinal Back/Paraspinal Thigh Shoulder Thigh Shoulder Shoulder Foot/Ankle Back/Paraspinal Neck Arm Thigh
5 9 4 6 5 7 2 5 5 3 3 8 4 7 3 7 3 10 4 2 6 6 8 8 6 3 10
tissues of the neck, back, and midline shoulder and onethird of the present cases occurred in deeper intramuscular or intermuscular locations. This differs from prior literature and indicates that age and location are not always helpful for differentiating SCL and other lipomatous lesions. In the present series, most SCLs contain visible fat on MRI or CT, but only 11% of the present cases had a unenhanced MRI appearance such as benign lipoma. Three of the present SCLs very closely resembled a lipoma. One of these did exhibit contrast enhancement and only a trace amount of high signal on the T2-weighted sequences. Two of the other lipoma-like cases exhibited contrast enhancement and
CT
YES YES YES
YES YES YES YES YES
% fat
MR Yes Contrast or w/o
>90 >90 >50 >90 <50 >50 >50 >90 <50 0 >50 >90 >50 >90 <50 >90 <50 0 0 0 <50 >50 >50 0 >50 <50 >50
w/o w/o yes yes yes yes w/o w/o w/o yes No MRI yes No MRI yes yes w/o yes yes yes yes yes yes w/o yes yes yes yes
<90
<90 <90
<90 <90
<90 <90 <90 <90
Enhancement
minimal moderate marked moderate
minimal minimal minimal minimal marked minimal marked marked marked moderate moderate marked marked marked
Edema no no minimal minimal minimal minimal no no no no no no no no no minimal minimal no no no no minimal no minimal minimal no no
showed minimal enhancement but more than the adjacent subcutaneous fat. Approximately 56% of the present SCLs contained fat but <90% fat, similar in appearance to highergrade liposarcomas. The most common imaging appearance of SCL is a tumour that contains between 50e90% fat, and therefore, likely resembles an ALT, WDLS, or hibernoma. One of the most important imaging characteristics observed is that most if not all SCLs showed some degree of enhancement. This is consistent with published series that show a very high percentage (91e100%) showing MRI contrast enhancement.7,11e13 In the present series, the degree of MRI contrast enhancement demonstrated a broad
Figure 5 A 62-year-old man with a 6 cm subcutaneous right shoulder mass, which was resected surgically and proven histopathologically to be a SCL. The lesion shows <50% fat. The lesion was predominantly hyperintense on T2-weighted fat-saturated sequences and was relatively well defined, with marked enhancement and no peripheral oedema. (a) Axial T1-weighted MRI image of the right shoulder showing a well-defined tumour with <50% fat. (b) Axial T2-weighted fat-saturated MRI image of the right shoulder showing a well-defined tumour with diffuse hyperintensity throughout the whole lesion and no peripheral oedema. (c) Axial T1-weighted fat-saturated post-intravenous gadolinium of the right shoulder showing marked contrast enhancement. Please cite this article as: Jelinek JS et al., Imaging of spindle cell lipoma, Clinical Radiology, https://doi.org/10.1016/j.crad.2019.11.020
J.S. Jelinek et al. / Clinical Radiology xxx (xxxx) xxx
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Figure 6 A 44-year-old man who went an MRI arthrogram with an incidental 4 cm shoulder mass of the subcutaneous tissues of the shoulder. Because a mass was seen, intravenous gadolinium was also given. The mass had no visible fat and was well defined. The lesion was uniformly hyperintense on T2-weighted fat-saturated sequences and showed marked enhancement. There was no peripheral oedema and the mass was resected surgically and proven histopathologically to be a SCL. (a) Sagittal T1-weighted MRI image of the shoulder shows a well-defined softtissue mass of the subcutaneous tissues without evidence of visible fat. An MRI arthrogram study performed showed contrast in the joint space. (b) Sagittal T2-weighted fat-saturated MRI image of the shoulder shows a well-defined soft-tissue mass of the subcutaneous tissues with diffuse hyperintensity. There is no peripheral oedema. The lesion appears “cystic”. (c) Sagittal T1-weighted fat-saturated MRI of the shoulder postintravenous and intra-articular contrast medium shows a well-defined soft-tissue mass with marked contrast enhancement.
range of enhancement from mild to moderate to marked intensity. This is in distinction to simple lipomas, which do not enhance with contrast medium. This can further lead to the erroneous diagnosis of a soft-tissue sarcoma. In the present series, SCLs demonstrated a range of tumour margin characteristics, which could raise the suspicion for potential malignancy. In contrast to conventional ALT and WDLS, whose margins are typically well defined to relatively well defined, 19% of SCLs in the present series were poorly defined. Peritumoural oedema was observed in onethird of the present cases, which has not been commented on in previous literature.20e22 It is important to note that this may not be a unique finding in SCL, as any tumour previously biopsied or traumatised may demonstrate peritumoural oedema on MRI. None of the present cases had been biopsied prior to imaging. In all of the present cases,
peritumoural oedema was minimal, when present. Other authors have described peritumoural oedema with a margin of 18 mm21 as more predictive of malignant softtissue tumours. Due to the varied imaging appearance of SCL, a definitive diagnosis requires complete histological evaluation of the entire tumour to avoid sampling error and missing rare lipoblasts that might be present in scant amounts within the tumour. Lipoblasts are univacuolar or multivacuolar malignant fat cells with enlarged, hyperchromatic nuclei. The fat vacuoles within these cells cause an indentation of the nucleus. The presence of true lipoblasts is diagnostic of a malignant adipose tissue tumour. Histopathologically, SCL are usually well circumscribed, but rarely encapsulated fatty tumours.1e5 Classic SCLs have three components histologically: fat, spindle cells, and ropey collagen (Figs 1 and 2), but their histology can vary
Figure 7 A 71-year-old man with a 6 cm subcutaneous mass of the right shoulder. The lesion had >50% but <90% fat content at both CT and MRI. The lesion was moderately hyperintense on T2 fat-saturated sequences, was relatively well defined, and showed moderate enhancement. There was very minimal oedema at the margins of the lesion, which was resected surgically and proven histopathologically to be a SCL. (a) Coronal T1weighted MRI of the right shoulder shows a lesion with >50% but <90% fat content. Margins are relatively well-defined. (b) Coronal T2-weighted fat-saturated MRI image of the right shoulder shows a lesion that is moderately heterogeneous and moderately hyperintense. It is relatively well defined. Minimal oedema is present along the margins of the lesion. (c) Coronal T1-weighted fat-saturated MRI image of the right shoulder after intravenous gadolinium shows the mass having moderate enhancement and minimal oedema along the margins. Please cite this article as: Jelinek JS et al., Imaging of spindle cell lipoma, Clinical Radiology, https://doi.org/10.1016/j.crad.2019.11.020
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widely from some SCLs having no fat (Fig 3) and some with extensive myxoid change (Fig 4). This histological variation explains the varied imaging characteristics of SCLs. SCL can be diagnosed with confidence on a core needle biopsy if it occurs in a typical location (neck, upper back) has typical imaging features (well circumscribed, superficial, presence of fat), and has the three aforementioned histological features. Diagnosis is more difficult if the tumour occurs in an atypical location (deep in the extremities) and has atypical imaging characteristics with corresponding atypical histology (absence of fat and/or extensive myxoid change). Moreover, some SCLs have lipoblast-like cells6,23,24 making their distinction from ALT/WDLS difficult on small-needle core biopsies. In such cases, immunostaining and/or molecular studies can help in reaching the correct diagnosis. Immunohistochemically, almost all SCLs have a diffuse and strong expression of CD34 of the spindle cells and are consistently negative for the Rb protein. Fluorescence in situ hybridisation (FISH) analysis for MDM2 and CDK4 amplification can help differentiate an SCL with lipoblast-like cells from ALT/WDLS.25,26 SCLs with extensive myxoid change can be confused with myxoid liposarcoma. Today rare cases, in particular in atypical locations, may need FISH analysis.25,26 Because of the highly variable and indeterminate appearance of these lesions, SCLs can pose a significant diagnostic challenge. Surgery for lipomatous tumours is planned with consideration of the likelihood of progression, local recurrence, and/or metastatic spread, which is dependent on an accurate histological diagnosis. Frequently, the diagnosis is not definitively made until after incisional or excisional surgical biopsy, when adequate tissue can be sampled for comprehensive analysis, and entities that are more aggressive are ruled out. This can make the approach to surgical planning difficult. As with lipomas and ALTs, marginal resection of the lesion from within the pseudo-capsule is considered an acceptable margin for spindle cell lipoma. Malignant liposarcomas require wide resection with negative surgical margins, frequently with adjuvant radiotherapy delivered in the preoperative or postoperative setting. When the diagnosis cannot be definitively made prior to surgery, the surgeon may be forced to decide between aborting after an incisional biopsy and returning for definitive resection at a later date, performing a marginal resection with a risk of inadequate margins should pathology demonstrate a malignancy, or pursuing a wide margin of resection that may be more aggressive than warranted for the diagnosis. Each of these options imparts risks to the patient. Lesions within the subcutaneous space can often be resected with a wide margin without additional morbidity, but deeper lesions may benefit from a more thorough diagnostic work-up prior to resection. The present series illustrates the hazards that the surgeon may encounter when SCLs are indeterminate on imaging. Overall, the prognosis for SCL is excellent after surgical resection. No patients in the present series developed local recurrence, but prior series suggest a 12% local recurrence rate, which is higher than lipoma.3 Limitations of this study included small sample size and retrospective analysis. Not all patients had unenhanced as well as
contrast-enhanced MRI and CT studies. Most histopathology specimens did not undergo advanced cytogenetic or molecular testing. SCLs have a considerably variable imaging appearance and may have minimal or no visible fat on MRI or CT making definitive diagnosis on imaging and clinical information challenging at best. Post-contrast enhancement is seen in all cases, which may further lead to misdiagnosis in favour of a malignant neoplasm. The imaging appearance may mimic lipoma, atypical lipomatous tumour, liposarcoma, and even high-grade soft-tissue sarcoma. The absence of fat or minimal fat on imaging should not dissuade the surgical oncologist that the histological diagnosis is incorrect, but is simply one of the imaging patterns of SCL that the present and other studies have shown. MDM2 testing to distinguish SCLs from ALT and liposarcoma is increasingly becoming utilised. By recognising the variable clinical and radiographic presentation of SCL, clinicians can understand a diagnosis of SCL can be made without visible fat on CT or MRI and can be similar in appearance to a higher-grade liposarcoma with only minimal fat.
Conflict of Interest The authors declare no conflict of interest.
References 1. Enzinger FM, Harvey DA. Spindle cell lipoma. Cancer 1975;36:1852e9. 2. Fletcher CD, Martin-Bates E. Spindle cell lipoma: a clinicopathological study with some original observations. Histopathology 1987;11:803e17. 3. Marino-Enriquez A, Nascimento AF, Ligon AH, et al. Atypical spindle cell lipomatous tumours: clinicopathologic characterization of 232 cases demonstrating a morphologic spectrum. Am J Surg Pathol 2017;41(2):234e44. 4. Ko JS, Daniels B, Emanuel PO, et al. Spindle cell lipoma in women: a report of 53 cases. Am J Surg Pathol 2017 Sept;41(9):1267e74. 5. Angervall L, Dahl I, Kindblom LG, et al. Spindle cell lipoma. Acta Pathol Microbiol Scand A 1976;84:477e87. 6. Beham A, Schmid C, Hodl S, et al. Spindle cell and pleomorphic lipoma: an immunohistochemical study and histogenetic analysis. J Pathol 1989;158:219e22. 7. Bancroft LW, Kransdorf MJ, Peterson JJ, et al. Imaging characteristics of spindle cell lipoma. AJR Am J Roentgenol 2003;181:1251e4. 8. Choi JW, Kim HJ, Kim J, et al. Spindle cell lipoma of the head and neck: CT and MRI imaging findings. Neuroradiology 2013 Jan;55(1):101e6. 9. Bui-Mansfield LT, Kaplan KJ. Spindle cell lipoma of the upper back. AJR Am J Roentgenol 2002;179:1158. 10. Braunschweig IJ, Stein IH, Dodwad MI, et al. Case report 751: Spindle cell lipoma causing marked bone erosion. Skeletal Radiol 1992;21:414e7. 11. Khashper A, Zheng J, Nahal A, et al. Imaging characteristics of spindle cell lipoma and its variants. Skeletal Radiol 2014;43(5):591e7. 12. Kirwadi A, Abdul-Halim R, Fernando M, et al. MRI imaging features of spindle cell lipoma. Skeletal Radiol 2014;43(2):191e6. 13. Younan Y, Martinez A, Reimer N, et al. Combined classical spindle cell/ pleomorphic lipoma spectrum imaging and clinical data. Skeletal Radiol 2018;47:51e9. 14. Bancroft LW, Kransdorf MJ, Peterson JJ, et al. Benign fatty tumour’s: classification, clinical course, imaging appearance, and treatment. Skeletal Radiol 2006;35(10):719e33. 15. Helms CA, Gaskin CM. Lipomas, lipoma variants, and well-differentiated liposarcomas (atypical lipomas): results of MRI evaluations of 126 consecutive fatty masses. AJR Am J Roentgenol 2004;182:733e9.
Please cite this article as: Jelinek JS et al., Imaging of spindle cell lipoma, Clinical Radiology, https://doi.org/10.1016/j.crad.2019.11.020
J.S. Jelinek et al. / Clinical Radiology xxx (xxxx) xxx 16. Jelinek JS, Kransdorf MJ, Shmookler BM, et al. Liposarcoma of the extremities: MRI and CT findings in the histologic subtypes. Radiology 1993;86:455e9. 17. Song T, Shen J, Liang BL, et al. Retroperitoneal liposarcoma: MRI characteristics and pathological correlative analysis. Abdom Imaging 2007;32(5):668e74. 18. Klevos G, Jose J, Pretell-Mazzini J, et al. Hibernoma Am J Orthoped 2015;44(5):284e7. 19. Papathanassiou Z, Alberghini M, Taieb S, et al. Imaging of hibernomas: a retrospective study on twelve cases. Clin Sarcoma Res 2011;1:3e14. 20. Wortman JR, Tirumani SH, Jagannathan JP, et al. Primary extremity liposarcoma: mri features, histopathology, and clinical outcomes. JCAT 2016;40(5):791e8. 21. Zhang Z, Deng L, Ding L, et al. MRI imaging differentiation of malignant soft tissue tumours from peripheral schwannomas with large size and heterogeneous signal intensity. Eur J Radiol 2015;84(5):940e6.
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22. Costa FM, Canella C, Gasparetto E. Advanced magnetic resonance imaging techniques in the techniques in the evaluation of musculoskeletal tumours. Radiol Clin North Am 2011;49(6):1325e58. 23. Kazakov MM, Hadravsky L, Michalova K, et al. Lipoblasts in spindle cell lipoma and pleomorphic lipomas: a close scrutiny. Hum Pathol 2017;65:140e6. 24. Machol JA, Cusic JG, O’Connor EA, et al. Spindle cell lipoma of the neck: review of the literature and case report. Plast Reconstr Surg 2015;3(11):e550. 25. Kulkarni AS, Wojcik JB, Chouqule A, et al. MDM2 RNA in situ hybridization for the diagnosis of atypical lipomatosis tumour: a study evaluating DNA, RNA, and protein expression. Am J Surg Pathol 2019;43(4):446e54. 26. Marino-Enriquez A, Nascimento AF, Ligon AH, et al. Atypical lipomatosis tumour: clinicopathologic characterization of 232 cases demonstrating a morphologic spectrum. Am J Surg Pathol 2017;41(2). 24-244.
Please cite this article as: Jelinek JS et al., Imaging of spindle cell lipoma, Clinical Radiology, https://doi.org/10.1016/j.crad.2019.11.020
Contents lists available at ScienceDirect
Clinical Radiology journal homepage: www.clinicalradiologyonline.net
Imaging of spindle cell lipoma J.S. Jelinek a, *, A. Wu b, M. Wallace c, D. Kumar a, R.M. Henshaw c, M.J. Murphey d, A. Van Horn c, A.J. Aboulafia c a
Department of Radiology, MedStar Washington Hospital Center, 110 Irving Street, NW, Washington DC, 20010, USA Department of Internal Medicine, MedStar Franklin Square Medical Center, 9000 Franklin Square Drive, Baltimore, MD, 21237, USA c Department of Orthopedic Oncology, MedStar Franklin Square Medical Center, 9000 Franklin Square Drive, Baltimore, MD, 21237, USA d American Institute for Radiologic Pathology, 1100 Wayne Avenue, Silver Spring, MD, 20910, USA b
art icl e i nformat ion Article history: Received 6 June 2019 Accepted 26 November 2019
AIM: To review the evaluation, diagnosis, and treatment of spindle cell lipoma (SCL) with emphasis on the location of these tumours and the spectrum of magnetic resonance imaging (MRI) and computed tomography (CT) appearances. MATERIALS AND METHODS: The MRI and CT findings of 27 histopathologically proven SCLs were evaluated retrospectively. Imaging features evaluated included margins, percentage visible fat, MRI signal characteristics, oedema, and contrast enhancement patterns. RESULTS: Patient ages ranged from 18 to 80 years with an average age of 56.5 years. Men were affected twice as frequently as women (M¼18, F¼9). SCLs ranged in size from 2 to 10 cm, with an average greatest dimension of 5.5 cm. Five lesions (19%) contained no visible fat on CT or MRI, and the leading differential diagnosis of high-grade soft-tissue sarcoma diagnosis was suggested by referring surgeons. Five lesions (19%) had <50% fatty areas, nine lesions (52%) demonstrated >50% but <90% fat at MRI or CT. Only three of 25 lesions (12%) had an appearance of a typical lipoma on unenhanced MRI sequences. All SCLs that were imaged with contrast medium (n ¼ 18) demonstrated some degree of enhancement, with eight (44%) showing marked enhancement, four (22%) showing moderate, and six (33%) minimal enhancement. CONCLUSION: SCLs have considerably variable imaging appearances and may have minimal or no visible fat at MRI or CT. Imaging features may make it difficult to distinguish this benign tumour from a potentially higher-grade malignant tumour. Ó 2019 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Introduction Spindle cell lipoma (SCL), first reported in 1975 (1), is a rare, slow-growing, benign variant of lipoma. SCL accounts
for approximately 1.5% of biopsy-analysed lipomas1e4 and are composed of mature adipocytes, uniformly proliferated spindle cells embedded within a rope-like collagen fibres and mucoid stroma.1e6 SCL typically presents as a welldefined heterogeneous subcutaneous mass. It has been
* Guarantor and correspondent: J. S. Jelinek, Department of Radiology. MedStar Washington Hospital Center, 110 Irving Street, NW, Washington DC, 20010, NW, USA, Tel.: þ1 202 877 6088. E-mail address: [email protected] (J.S. Jelinek). https://doi.org/10.1016/j.crad.2019.11.020 0009-9260/Ó 2019 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Please cite this article as: Jelinek JS et al., Imaging of spindle cell lipoma, Clinical Radiology, https://doi.org/10.1016/j.crad.2019.11.020
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reported to occur most commonly in middle-aged men (10:1 male-to-female ratio) between 45 and 70 years (a mean of 54 years) with a predilection for the “shawl area” (shoulder, posterior neck, and upper back).1,2,5,6 In clinical practice, the present authors found the classic description of sex, age, and location SCL to be less accurate than reported previously. Unlike lipoma, SCL appearance at MRI is not characteristic, and is easily misdiagnosed as a softtissue sarcoma.7e10 Their uncharacteristic MRI imaging has been described in radiology journals,7e13 but the surgical practitioner must likewise be aware of the diagnostic challenges of this unusual entity. The wide spectrum of imaging appearances can be confused with lipomas, atypical lipomatous tumours (ALT), well-differentiated liposarcoma (WDLS), and high-grade soft-tissue sarcomas.13e15 MRI is nearly 100% accurate in the diagnosis of simple lipoma, and can further identify features suggestive of atypical lipomatous tumour. Pathologically, however, SCLs may show a significant amount of fat, minimal fat, or no fat (Figs 1e4). MRI reflects the gross morphology of the lesion, which often has potential for misdiagnosis.7,11 Although histological examination is the reference standard for diagnosis, clinical presentation and imaging may offer a more accurate preoperative assessment to assist the surgeon in choosing the preferred method of biopsy, resection, or observation. The purpose of the present study was to review the evaluation, diagnosis, and treatment of SCL with emphasis on the location of these tumours and the spectrum of MRI and CT appearances.
Figure 2 Cellular area of tumour showing spindle cells separated by dense collagen (haematoxylin and eosin staining, 200).
Materials and methods After institutional IRB review and approval, the clinical, surgery, pathology, and radiology databases were reviewed retrospectively for the diagnosis of SCL for the years 2006e2015. Inclusion criteria included a final histopathological diagnosis of SCL after tumour resection, and available clinical data and preoperative evaluation by MRI, CT, or
Figure 1 Admixture of mature fat and spindle cells (haematoxylin and eosin staining, 40).
Figure 3 Fat-free SCL (haematoxylin and eosin staining, 200).
Figure 4 SCL with extensive myxoid change (haematoxylin and eosin staining, 200).
Please cite this article as: Jelinek JS et al., Imaging of spindle cell lipoma, Clinical Radiology, https://doi.org/10.1016/j.crad.2019.11.020
J.S. Jelinek et al. / Clinical Radiology xxx (xxxx) xxx
both. MRI studies needed to have a minimum of two orthogonal planes and include typical T1-weighted and fatsuppressed T2-weighted or STIR (short T1 inversion recovery) sequences. CT studies were performed without intravenous contrast medium using a multidetector CT system. A total of 27 surgically resected and histopathologically proven SCLs that met inclusion criteria from two busy orthopaedic oncology practices were identified. A dedicated musculoskeletal radiologist and a fellowship-trained orthopaedic surgical oncologist reviewed the records and imaging of all cases independently. Evaluation included patient demographics, size, anatomical location, compartment location, and imaging features on MRI (n ¼ 25) and CT (n ¼ 7). Seven patients had both CT and MRI. Tumour location was assessed for the anatomical region of the body as well as the relationship to the subcutaneous (superficial) space above the fascia versus deep intramuscular or deep intermuscular compartments. Tumour size was measured in centimetres at its greatest dimensions. Imaging features evaluated included margins, percentage visible fat, CT attenuation, and MRI signal characteristics and enhancement pattern. Lesion margin was assessed as a well-defined capsule (rim of low-signal intensity tissue), defined without a capsule, or as poorly defined (no borders). The percentage of visible fat within the tumour was assessed subjectively based on the amount of fat (density on CT and iso-intensity to fat-on non-fatsaturated T1-weighted MRI images) within the entire lesion using the axial, sagittal, and coronal images. Fat content was scored as no fat, <50% fat, >50 but <90% fat and >90%. The degree of enhancement was assessed subjectively as none, minimal, moderate, or marked on the contrast-enhanced fat-saturated T1-weighted images as compared to the unenhanced T1-weighted images and the adjacent subcutaneous fat. Peripheral oedema was again subjective comparing high signal around the lesion on the fatsaturated T2-weighted or STIR sequences as compared to adjacent subcutaneous fat. The MRI signal intensity of the mass was assessed on both T1-and T2-weighted fatsuppressed or STIR sequences. Clinical follow-up for tumour recurrence was assessed by review of the clinical databases with a minimum of 3 years and a maximum of 11 years.
Results Patient ages ranged from 18 to 80 years with an average age of 56.5 years. Men were affected only twice as frequently as women (M¼18, F¼9). The most common locations included flank/paraspinal (24%), neck (20%), shoulder (16%), foot/ankle (12%), and other (28%). SCLs were observed most commonly in the subcutaneous fat (67%), followed by intermuscular (19%) and intramuscular (15%) intervals. SCLs ranged in size from 2 cm to a maximum dimension of 10 cm, with an average greatest dimension of 5.5 cm. Evaluation of tumour margins demonstrated that 11 (40%) were very well defined, 11 (40%) were relatively well defined, and five (19%) were poorly defined (Table 1).
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Analysis of visible fat content revealed five (19%) lesions contained no visible fat on CT or MRI. Six lesions (22%) of SCLs had 50% fat. Nine lesions (33%) had >50% but <90% fat at MRI or CT (Figs 5e7). Only three of 25 (12%) lesions were iso-intense to the adjacent subcutaneous fat on noncontrast MRI sequences, consistent with the overall appearance of lipoma. One of these did not show contrast and could not be discerned from lipoma. The other two had increased enhancement greater than adjacent subcutaneous fat. On MRI, 22 of 25 (88%) demonstrated varying degrees of hyperintensity on T2-weighted/STIR sequences. Peritumoural oedema was noted in nine of 25 (36%) cases of SCL on MRI, all of which were characterised as minimal. No cases of oedema were identified by CT. There were no tumours with moderate to marked peritumoural oedema. All SCLs evaluated with contrast-enhanced MRI studies (n ¼ 18) demonstrated enhancement (Figs 5e7). Eight lesions (44%) were characterised by marked enhancement, six lesions (33%) showed moderate enhancement, and four lesions (22%) demonstrated minimal enhancement. CT was performed without contrast medium and enhancement could not be assessed (Table 1). Clinically, all patients underwent complete en-bloc surgical resection with a marginal to wide surgical margin. There were no major surgical complications, and there have been no reported local recurrences.
Discussion Historically, the imaging of lipomas and liposarcomas has been oversimplified; tumours that were identical to subcutaneous fat on all MRI sequences were lipomas. Predominantly fatty tumours with areas of significant enhancement or high signal intensity on T2-weighted images likely represented ALT if located in the extremities or WDLS if in the retroperitoneum15e17; however, there are other benign fatty tumours that may have indeterminate imaging characteristics such as ALT and liposarcoma. Hibernomas18 are a well-known, albeit much rarer, entity, which can have similar imaging characteristics to either lipoma or liposarcoma.18,19 SCLs are being increasingly recognised for their wide spectrum of imaging appearances and are more common than hibernomas. SCL imaging appearances range from an appearance resembling that of a simple lipoma, To more cellular lesions with T2-weighted hyperintensity that may mimic ALT, to lesions with scant or absent fatty content, suggestive of a soft-tissue sarcoma.7e13 Classic teaching has described SCL as an entity almost exclusively seen in older men in a “shawl” distribution covering the posterior neck, midline of the upper back and medial shoulders.1,2 Furthermore, these were described as classically subcutaneous, superficial lesions. The present series demonstrated a 2:1 ratio of males-tofemales, which is much lower than the previously reported 10:1 ratio.1,2,9,13 There was a wide range of patient ages, which is different from most prior reports that describe 90% of SCLs as occurring in older men.1e5,9,12 Less than half of the present cases occurred in the subcutaneous
Please cite this article as: Jelinek JS et al., Imaging of spindle cell lipoma, Clinical Radiology, https://doi.org/10.1016/j.crad.2019.11.020
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Table 1 Spindle Cell Lipoma Case Data. Patient #
Age
Sex
Location
Location
Largest Size (cm)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 19 20 21 22 23 24 25 18 26 27
59 65 48 47 33 63 78 80 52 48 63 24 39 75 65 46 71 79 44 18 62 71 24 71 73 65 64
F F M M M M F M M F M F M M M F M F M M M M F M M F M
Subcutaneous Intramuscular Subcutaneous Intermuscular Subcutaneous Subcutaneous Subcutaneous Subcutaneous Intramuscular Subcutaneous Subcutaneous Subcutaneous Subcutaneous Subcutaneous Intermuscular Intramuscular Intermuscular Intermuscular Subcutaneous Intermuscular Subcutaneous Subcutaneous Subcutaneous Subcutaneous Subcutaneous Subcutaneous Intramuscular
Foot/Ankle Back/Paraspinal Knee Shoulder Shoulder Knee Foot/Ankle Back/Paraspinal Neck Arm Neck Back/Paraspinal Neck Neck Arm Back/Paraspinal Back/Paraspinal Thigh Shoulder Thigh Shoulder Shoulder Foot/Ankle Back/Paraspinal Neck Arm Thigh
5 9 4 6 5 7 2 5 5 3 3 8 4 7 3 7 3 10 4 2 6 6 8 8 6 3 10
tissues of the neck, back, and midline shoulder and onethird of the present cases occurred in deeper intramuscular or intermuscular locations. This differs from prior literature and indicates that age and location are not always helpful for differentiating SCL and other lipomatous lesions. In the present series, most SCLs contain visible fat on MRI or CT, but only 11% of the present cases had a unenhanced MRI appearance such as benign lipoma. Three of the present SCLs very closely resembled a lipoma. One of these did exhibit contrast enhancement and only a trace amount of high signal on the T2-weighted sequences. Two of the other lipoma-like cases exhibited contrast enhancement and
CT
YES YES YES
YES YES YES YES YES
% fat
MR Yes Contrast or w/o
>90 >90 >50 >90 <50 >50 >50 >90 <50 0 >50 >90 >50 >90 <50 >90 <50 0 0 0 <50 >50 >50 0 >50 <50 >50
w/o w/o yes yes yes yes w/o w/o w/o yes No MRI yes No MRI yes yes w/o yes yes yes yes yes yes w/o yes yes yes yes
<90
<90 <90
<90 <90
<90 <90 <90 <90
Enhancement
minimal moderate marked moderate
minimal minimal minimal minimal marked minimal marked marked marked moderate moderate marked marked marked
Edema no no minimal minimal minimal minimal no no no no no no no no no minimal minimal no no no no minimal no minimal minimal no no
showed minimal enhancement but more than the adjacent subcutaneous fat. Approximately 56% of the present SCLs contained fat but <90% fat, similar in appearance to highergrade liposarcomas. The most common imaging appearance of SCL is a tumour that contains between 50e90% fat, and therefore, likely resembles an ALT, WDLS, or hibernoma. One of the most important imaging characteristics observed is that most if not all SCLs showed some degree of enhancement. This is consistent with published series that show a very high percentage (91e100%) showing MRI contrast enhancement.7,11e13 In the present series, the degree of MRI contrast enhancement demonstrated a broad
Figure 5 A 62-year-old man with a 6 cm subcutaneous right shoulder mass, which was resected surgically and proven histopathologically to be a SCL. The lesion shows <50% fat. The lesion was predominantly hyperintense on T2-weighted fat-saturated sequences and was relatively well defined, with marked enhancement and no peripheral oedema. (a) Axial T1-weighted MRI image of the right shoulder showing a well-defined tumour with <50% fat. (b) Axial T2-weighted fat-saturated MRI image of the right shoulder showing a well-defined tumour with diffuse hyperintensity throughout the whole lesion and no peripheral oedema. (c) Axial T1-weighted fat-saturated post-intravenous gadolinium of the right shoulder showing marked contrast enhancement. Please cite this article as: Jelinek JS et al., Imaging of spindle cell lipoma, Clinical Radiology, https://doi.org/10.1016/j.crad.2019.11.020
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Figure 6 A 44-year-old man who went an MRI arthrogram with an incidental 4 cm shoulder mass of the subcutaneous tissues of the shoulder. Because a mass was seen, intravenous gadolinium was also given. The mass had no visible fat and was well defined. The lesion was uniformly hyperintense on T2-weighted fat-saturated sequences and showed marked enhancement. There was no peripheral oedema and the mass was resected surgically and proven histopathologically to be a SCL. (a) Sagittal T1-weighted MRI image of the shoulder shows a well-defined softtissue mass of the subcutaneous tissues without evidence of visible fat. An MRI arthrogram study performed showed contrast in the joint space. (b) Sagittal T2-weighted fat-saturated MRI image of the shoulder shows a well-defined soft-tissue mass of the subcutaneous tissues with diffuse hyperintensity. There is no peripheral oedema. The lesion appears “cystic”. (c) Sagittal T1-weighted fat-saturated MRI of the shoulder postintravenous and intra-articular contrast medium shows a well-defined soft-tissue mass with marked contrast enhancement.
range of enhancement from mild to moderate to marked intensity. This is in distinction to simple lipomas, which do not enhance with contrast medium. This can further lead to the erroneous diagnosis of a soft-tissue sarcoma. In the present series, SCLs demonstrated a range of tumour margin characteristics, which could raise the suspicion for potential malignancy. In contrast to conventional ALT and WDLS, whose margins are typically well defined to relatively well defined, 19% of SCLs in the present series were poorly defined. Peritumoural oedema was observed in onethird of the present cases, which has not been commented on in previous literature.20e22 It is important to note that this may not be a unique finding in SCL, as any tumour previously biopsied or traumatised may demonstrate peritumoural oedema on MRI. None of the present cases had been biopsied prior to imaging. In all of the present cases,
peritumoural oedema was minimal, when present. Other authors have described peritumoural oedema with a margin of 18 mm21 as more predictive of malignant softtissue tumours. Due to the varied imaging appearance of SCL, a definitive diagnosis requires complete histological evaluation of the entire tumour to avoid sampling error and missing rare lipoblasts that might be present in scant amounts within the tumour. Lipoblasts are univacuolar or multivacuolar malignant fat cells with enlarged, hyperchromatic nuclei. The fat vacuoles within these cells cause an indentation of the nucleus. The presence of true lipoblasts is diagnostic of a malignant adipose tissue tumour. Histopathologically, SCL are usually well circumscribed, but rarely encapsulated fatty tumours.1e5 Classic SCLs have three components histologically: fat, spindle cells, and ropey collagen (Figs 1 and 2), but their histology can vary
Figure 7 A 71-year-old man with a 6 cm subcutaneous mass of the right shoulder. The lesion had >50% but <90% fat content at both CT and MRI. The lesion was moderately hyperintense on T2 fat-saturated sequences, was relatively well defined, and showed moderate enhancement. There was very minimal oedema at the margins of the lesion, which was resected surgically and proven histopathologically to be a SCL. (a) Coronal T1weighted MRI of the right shoulder shows a lesion with >50% but <90% fat content. Margins are relatively well-defined. (b) Coronal T2-weighted fat-saturated MRI image of the right shoulder shows a lesion that is moderately heterogeneous and moderately hyperintense. It is relatively well defined. Minimal oedema is present along the margins of the lesion. (c) Coronal T1-weighted fat-saturated MRI image of the right shoulder after intravenous gadolinium shows the mass having moderate enhancement and minimal oedema along the margins. Please cite this article as: Jelinek JS et al., Imaging of spindle cell lipoma, Clinical Radiology, https://doi.org/10.1016/j.crad.2019.11.020
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widely from some SCLs having no fat (Fig 3) and some with extensive myxoid change (Fig 4). This histological variation explains the varied imaging characteristics of SCLs. SCL can be diagnosed with confidence on a core needle biopsy if it occurs in a typical location (neck, upper back) has typical imaging features (well circumscribed, superficial, presence of fat), and has the three aforementioned histological features. Diagnosis is more difficult if the tumour occurs in an atypical location (deep in the extremities) and has atypical imaging characteristics with corresponding atypical histology (absence of fat and/or extensive myxoid change). Moreover, some SCLs have lipoblast-like cells6,23,24 making their distinction from ALT/WDLS difficult on small-needle core biopsies. In such cases, immunostaining and/or molecular studies can help in reaching the correct diagnosis. Immunohistochemically, almost all SCLs have a diffuse and strong expression of CD34 of the spindle cells and are consistently negative for the Rb protein. Fluorescence in situ hybridisation (FISH) analysis for MDM2 and CDK4 amplification can help differentiate an SCL with lipoblast-like cells from ALT/WDLS.25,26 SCLs with extensive myxoid change can be confused with myxoid liposarcoma. Today rare cases, in particular in atypical locations, may need FISH analysis.25,26 Because of the highly variable and indeterminate appearance of these lesions, SCLs can pose a significant diagnostic challenge. Surgery for lipomatous tumours is planned with consideration of the likelihood of progression, local recurrence, and/or metastatic spread, which is dependent on an accurate histological diagnosis. Frequently, the diagnosis is not definitively made until after incisional or excisional surgical biopsy, when adequate tissue can be sampled for comprehensive analysis, and entities that are more aggressive are ruled out. This can make the approach to surgical planning difficult. As with lipomas and ALTs, marginal resection of the lesion from within the pseudo-capsule is considered an acceptable margin for spindle cell lipoma. Malignant liposarcomas require wide resection with negative surgical margins, frequently with adjuvant radiotherapy delivered in the preoperative or postoperative setting. When the diagnosis cannot be definitively made prior to surgery, the surgeon may be forced to decide between aborting after an incisional biopsy and returning for definitive resection at a later date, performing a marginal resection with a risk of inadequate margins should pathology demonstrate a malignancy, or pursuing a wide margin of resection that may be more aggressive than warranted for the diagnosis. Each of these options imparts risks to the patient. Lesions within the subcutaneous space can often be resected with a wide margin without additional morbidity, but deeper lesions may benefit from a more thorough diagnostic work-up prior to resection. The present series illustrates the hazards that the surgeon may encounter when SCLs are indeterminate on imaging. Overall, the prognosis for SCL is excellent after surgical resection. No patients in the present series developed local recurrence, but prior series suggest a 12% local recurrence rate, which is higher than lipoma.3 Limitations of this study included small sample size and retrospective analysis. Not all patients had unenhanced as well as
contrast-enhanced MRI and CT studies. Most histopathology specimens did not undergo advanced cytogenetic or molecular testing. SCLs have a considerably variable imaging appearance and may have minimal or no visible fat on MRI or CT making definitive diagnosis on imaging and clinical information challenging at best. Post-contrast enhancement is seen in all cases, which may further lead to misdiagnosis in favour of a malignant neoplasm. The imaging appearance may mimic lipoma, atypical lipomatous tumour, liposarcoma, and even high-grade soft-tissue sarcoma. The absence of fat or minimal fat on imaging should not dissuade the surgical oncologist that the histological diagnosis is incorrect, but is simply one of the imaging patterns of SCL that the present and other studies have shown. MDM2 testing to distinguish SCLs from ALT and liposarcoma is increasingly becoming utilised. By recognising the variable clinical and radiographic presentation of SCL, clinicians can understand a diagnosis of SCL can be made without visible fat on CT or MRI and can be similar in appearance to a higher-grade liposarcoma with only minimal fat.
Conflict of Interest The authors declare no conflict of interest.
References 1. Enzinger FM, Harvey DA. Spindle cell lipoma. Cancer 1975;36:1852e9. 2. Fletcher CD, Martin-Bates E. Spindle cell lipoma: a clinicopathological study with some original observations. Histopathology 1987;11:803e17. 3. Marino-Enriquez A, Nascimento AF, Ligon AH, et al. Atypical spindle cell lipomatous tumours: clinicopathologic characterization of 232 cases demonstrating a morphologic spectrum. Am J Surg Pathol 2017;41(2):234e44. 4. Ko JS, Daniels B, Emanuel PO, et al. Spindle cell lipoma in women: a report of 53 cases. Am J Surg Pathol 2017 Sept;41(9):1267e74. 5. Angervall L, Dahl I, Kindblom LG, et al. Spindle cell lipoma. Acta Pathol Microbiol Scand A 1976;84:477e87. 6. Beham A, Schmid C, Hodl S, et al. Spindle cell and pleomorphic lipoma: an immunohistochemical study and histogenetic analysis. J Pathol 1989;158:219e22. 7. Bancroft LW, Kransdorf MJ, Peterson JJ, et al. Imaging characteristics of spindle cell lipoma. AJR Am J Roentgenol 2003;181:1251e4. 8. Choi JW, Kim HJ, Kim J, et al. Spindle cell lipoma of the head and neck: CT and MRI imaging findings. Neuroradiology 2013 Jan;55(1):101e6. 9. Bui-Mansfield LT, Kaplan KJ. Spindle cell lipoma of the upper back. AJR Am J Roentgenol 2002;179:1158. 10. Braunschweig IJ, Stein IH, Dodwad MI, et al. Case report 751: Spindle cell lipoma causing marked bone erosion. Skeletal Radiol 1992;21:414e7. 11. Khashper A, Zheng J, Nahal A, et al. Imaging characteristics of spindle cell lipoma and its variants. Skeletal Radiol 2014;43(5):591e7. 12. Kirwadi A, Abdul-Halim R, Fernando M, et al. MRI imaging features of spindle cell lipoma. Skeletal Radiol 2014;43(2):191e6. 13. Younan Y, Martinez A, Reimer N, et al. Combined classical spindle cell/ pleomorphic lipoma spectrum imaging and clinical data. Skeletal Radiol 2018;47:51e9. 14. Bancroft LW, Kransdorf MJ, Peterson JJ, et al. Benign fatty tumour’s: classification, clinical course, imaging appearance, and treatment. Skeletal Radiol 2006;35(10):719e33. 15. Helms CA, Gaskin CM. Lipomas, lipoma variants, and well-differentiated liposarcomas (atypical lipomas): results of MRI evaluations of 126 consecutive fatty masses. AJR Am J Roentgenol 2004;182:733e9.
Please cite this article as: Jelinek JS et al., Imaging of spindle cell lipoma, Clinical Radiology, https://doi.org/10.1016/j.crad.2019.11.020
J.S. Jelinek et al. / Clinical Radiology xxx (xxxx) xxx 16. Jelinek JS, Kransdorf MJ, Shmookler BM, et al. Liposarcoma of the extremities: MRI and CT findings in the histologic subtypes. Radiology 1993;86:455e9. 17. Song T, Shen J, Liang BL, et al. Retroperitoneal liposarcoma: MRI characteristics and pathological correlative analysis. Abdom Imaging 2007;32(5):668e74. 18. Klevos G, Jose J, Pretell-Mazzini J, et al. Hibernoma Am J Orthoped 2015;44(5):284e7. 19. Papathanassiou Z, Alberghini M, Taieb S, et al. Imaging of hibernomas: a retrospective study on twelve cases. Clin Sarcoma Res 2011;1:3e14. 20. Wortman JR, Tirumani SH, Jagannathan JP, et al. Primary extremity liposarcoma: mri features, histopathology, and clinical outcomes. JCAT 2016;40(5):791e8. 21. Zhang Z, Deng L, Ding L, et al. MRI imaging differentiation of malignant soft tissue tumours from peripheral schwannomas with large size and heterogeneous signal intensity. Eur J Radiol 2015;84(5):940e6.
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22. Costa FM, Canella C, Gasparetto E. Advanced magnetic resonance imaging techniques in the techniques in the evaluation of musculoskeletal tumours. Radiol Clin North Am 2011;49(6):1325e58. 23. Kazakov MM, Hadravsky L, Michalova K, et al. Lipoblasts in spindle cell lipoma and pleomorphic lipomas: a close scrutiny. Hum Pathol 2017;65:140e6. 24. Machol JA, Cusic JG, O’Connor EA, et al. Spindle cell lipoma of the neck: review of the literature and case report. Plast Reconstr Surg 2015;3(11):e550. 25. Kulkarni AS, Wojcik JB, Chouqule A, et al. MDM2 RNA in situ hybridization for the diagnosis of atypical lipomatosis tumour: a study evaluating DNA, RNA, and protein expression. Am J Surg Pathol 2019;43(4):446e54. 26. Marino-Enriquez A, Nascimento AF, Ligon AH, et al. Atypical lipomatosis tumour: clinicopathologic characterization of 232 cases demonstrating a morphologic spectrum. Am J Surg Pathol 2017;41(2). 24-244.
Please cite this article as: Jelinek JS et al., Imaging of spindle cell lipoma, Clinical Radiology, https://doi.org/10.1016/j.crad.2019.11.020