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Parosteal lipoma of the rib
Journal of Clinical Imaging 27 (2003) 435 – 437
Parosteal lipoma of the rib CT findings and pathologic correlation M. Imbriacoa,*, R. Ignarraa, N. De Rosab, G. Lambiaseb, M. Romanoa, A. Ragozzinoc a
Department of Radiology and I.B.B., University ‘‘Federico II,’’ Napoli, Italy b Department of Pathology, Monaldi Hospital, Napoli, Italy c Department of Radiology, Cardarelli Hospital, Napoli, Italy Received 26 October 2002
Abstract Parosteal lipoma is a rare benign tumor composed of adipose tissue contiguous to the periosteum of the underlying bone. These tumors are slow-growing, nontender masses that affect, almost exclusively, the diaphysis of the long bones of the upper and lower limbs. We hereby describe the CT characteristics with the correlative pathological findings in a rare case of parosteal lipoma of the rib. D 2003 Elsevier Inc. All rights reserved. Keywords: Parosteal lipoma; Rib; CT
1. Introduction Parosteal lipoma is a rare benign neoplasm composed mainly of mature adipose tissue that is contiguous to the underlying periosteal bone [1]. This neoplasm comprises 0.3% of all lipomas, and typically the most common location involved are the femur, proximal radius, humerus, tibia, clavicle and pelvis [2,3]. To the best of our knowledge, of the approximately 150 cases of parosteal lipoma reported in the literature, only 1 case has been previously described of parosteal lipoma of the rib [4]. We hereby describe the CT characteristics with the correlative pathologic findings in an exceedingly rare case of parosteal lipoma of the rib.
Clinical examination revealed a hard, nontender mass at the level of the right posterior fourth rib. Past medical history was unremarkable. On admission, a CT scan (Fig. 1) was obtained that showed a well-defined nonhomogeneous lobulated mass of fat attenuation attached to the lateral aspect of the right posterior fourth rib with the presence of a bony density arborisation within it and no evidence of inflammation or invasion of the adjacent muscles. The
2. Case report A 60-year-old man was admitted to our hospital with a 4-month history of progressive painful palpable mass at the level of the right posterior upper chest, which in the 3 weeks prior to admission had become more constant and intense.
* Corresponding author. Via Manzoni 214/0, Parco Flory, Isolato 4, Apt. 1, Napoli, Italy. Tel.: +39-81-5757370; fax: +39-81-5457081. E-mail address: [email protected] (M. Imbriaco). 0899-7071/03/$ – see front matter D 2003 Elsevier Inc. All rights reserved. doi:10.1016/S0899-7071(03)00010-X
Fig. 1. CT scan showing a well-defined lobulated mass of fat attenuation attached to the lateral aspect of the right posterior fourth rib with the presence of a bony arborisation within it.
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M. Imbriaco et al. / Journal of Clinical Imaging 27 (2003) 435–437
Fig. 2. Gross specimen showing a 5 3.5 mass with a lobulated fatty appearance attached to the rib.
presence of 60 and 100 Hounsfield Unit throughout the lesion confirmed that the mass was mainly composed of adipose tissue with only thin fibrous septa within it. Subsequently, the patient underwent en bloc resection of the mass and of the right fourth rib. The specimen was formalinfixed and paraffin-embedded. A total of 5-m-thick sections were obtained for histological examination and were stained with hematoxylin and eosin. Gross pathologic inspection of the lesion showed an encapsulated, circumscribed rounded mass of 5 3.5 cm in size, firm, with pushing margins. In addition, it showed a lobulated cut surface, yellowish, of adipose appearance, with solid whitish and translucent areas (Fig. 2). Microscopically, the lesion was circumscribed by a thin fibrous capsule and mainly constituted by mature adipose tissue. Interspersed islands of metaplastic bone and cartilage were observed in this tissue. Adipocytes were benign without evidence of atypias or pleomorphism (Figs. 3 and 4). Mitosis or necrosis were not appreciated.
Fig. 3. Histopathologic specimen showing mature adipose tissue containing areas of bone differentiation and small vessels (hematoxylin and eosin 100 ).
Fig. 4. High power view showing areas of condroid differentiation. All the tissues are well-differentiated without evidence of atypias or mitosis (hematoxylin and eosin 400 ).
The final diagnosis was consistent with parosteal lipoma of the rib. After the surgical excision of the mass, the patient had an uneventful postoperative course with no evidence of local recurrence 26 months after surgery.
3. Discussion Parosteal lipoma are rare and usually asymptomatic benign lesions found by definition in close or direct apposition to bone, representing 0– 3% of all lipomas [2]. Parostal, rather than periosteal lipoma, is the preferred terminology since the fat cells are not found in the periosteum itself [2]. These tumors commonly affect adults in the fifth decade of life, with range of 3 –84 years, without predominance of sex. Since their original description by Seerig in 1836, various reviews in the English literature regarding this rare entity have been published over the years [5]. The majority of these lesions are located adjacent to the long bones and especially to the femur (in approximately one-third of the cases) [2]. The most common presenting symptom is that of a slow-growing, large, nontender, immobile mass not fixed to the skin. Occasionally, disturbances in motor and sensory function of adjacent nerves may occur due to local pressure, resulting in muscle atrophy [6]. Parosteal lipoma may be large enough to cause limitation of joint motion or to compress a vital structure, such as an artery, nerve or lymphatics. In addition, these lesions may vary in size, measuring up to 18 cm in maximal dimension, although they usually maintain an indolent growth pattern. The treatment of choice is surgical excision. Pathologically, a parosteal lipoma is circumscribed by a thin, fibrous capsule. The multilobulated mass has a broad base attachment to the underlying bone [7]. Occasionally, a cartilage cap covers the bony trabeculae, yielding an osteo-
M. Imbriaco et al. / Journal of Clinical Imaging 27 (2003) 435–437
chondromatous appearance. Microscopically, the fat cells of a parosteal lipoma appear histochemically identical to adipocites found in the subcutaneous tissues [8,9]. Islands of calcifications or bone may occur within the lipoma. These islands have been attributed to metaplasia of preexisting mesenchymal cells. There is no indication to date that this tumor undergoes malignant degeneration, although minimal cellular pleomorphism may occasionally occur. Radiographically, the most characteristic feature demonstrates a well-defined area of lucency adjacent to the cortical bone commonly associated with reactive changes in the underlying cortex. In particular, reactive changes of the underlying bone include focal cortical hyperostosis and osseous bowing or a shallow erosion of the outer surface of the subjacent bone cortex [10]. Prior authors have attributed these cortical erosions to long-standing pressure on the cortex by the soft tissue mass. On CT scan, parosteal lipomas usually present as welldefined mass almost entirely composed of mature adipose tissue, with an osseous excrescence within it and/or erosion at the attachment of the soft-tissue mass to the subjacent cortex. As in the case presented, the axial CT images are useful to define the relationship of the mass with the adjacent bone and can help to exclude a malignant process. In particular, liposarcoma may have a component of mature fat, but unlike lipomas they are poorly defined and heterogeneous and contain confluent soft-tissue densities (as opposed to the thin fibrous septa of a lipoma). In addition, liposarcomas may invade adjacent structures with possible distant metastasis [11]. Rarely, benign atypical lipomas may exist having large areas of dense collagen and giant cells [12]. In these cases, a biopsy would be necessary to establish the benign or malignant nature of the lesion. Multiplanar reconstruction CT images are helpful in evaluating the extent of the tumor and the relationship of the bone excrescence to the cortex of the adjacent bone and to the surrounding, uninvolved but possibly displaced structures. CT scan can also confirm the indolent nature of this lesion
437
showing mechanical displacement rather than invasion of the adjacent structures. In summary, we have described a rare case of parosteal lipoma of the rib with CT and pathologic correlation.
Acknowledgments The authors sincerely thank Graciana Diez-Roux for critically reviewing this paper and Mrs. Carmela Imparato for editing the manuscript.
References [1] Murphey MD, Johnson DL, Bhatia PS, Neff JR, Rosenthal HG, Walker CW. Parosteal lipoma: MR imaging characteristics. AJR Am J Roentgenol 1994;162:105 – 10. [2] Fleming RJ, Alpert M, Garcia A. Parostal lipoma. AJR Am J Roentgenol 1962;87:1075 – 84. [3] Bui-Mansfield LT, Myers CP, Chew FS. Parosteal lipoma of the fibula. AJR Am J Roentgenol 2000;174:1698. [4] Fiorentino L, Rossi G, Ruggiero C, Valli R, Gusolfino D, Massimiano M, Losi L, Barbolini G. Parosteal lipoma of the rib: report of a case. Pathologica 2001;93:668 – 71. [5] Kawashima A, Magid D, Fishman EK, Hruban RH, Ney DR. Parosteal ossifying lipoma: CT and MR findings. J Comput Assist Tomogr 1993;17:147 – 50. [6] Kim JY, Jung SL, Pak YH, Kang YK. Parostal lipoma with hyperostosis. Eur Radiol 1999;9:1810 – 2. [7] Yu JS, Weis L, Becker W. MR imaging of a parosteal lipoma. Clin Imaging 2000;24:15 – 8. [8] Kransdorf MJ, Moser RP, Mesi JM, Meyer CA. Fat-containing soft tissue masses of the extremities. Radiographics 1991;11:81 – 106. [9] Miller MD, Ragsdale BD, Sweet DE. Parosteal lipoma: a new perspective. Pathology 1992;24:132 – 9. [10] Demos TC, Bruno E, Armin A, Dobozi WR. Parosteal lipoma with enlarging osteochondroma. AJR Am J Roentgenol 1984;143:365 – 6. [11] Munk PL, Lee MJ, Janzen DL, Connel DG, Logan PM, Poon PY, Bainbridge TC. Lipoma and liposarcoma: evaluation using CT and MR imaging. AJR Am J Roentgenol 1997;169:589 – 94. [12] Bush CH, Spanier SS, Gillespy T. Imaging of atypical lipomas of the extremities: report of three cases. Skeletal Radiol 1988;17:472 – 5.
Parosteal lipoma of the rib CT findings and pathologic correlation M. Imbriacoa,*, R. Ignarraa, N. De Rosab, G. Lambiaseb, M. Romanoa, A. Ragozzinoc a
Department of Radiology and I.B.B., University ‘‘Federico II,’’ Napoli, Italy b Department of Pathology, Monaldi Hospital, Napoli, Italy c Department of Radiology, Cardarelli Hospital, Napoli, Italy Received 26 October 2002
Abstract Parosteal lipoma is a rare benign tumor composed of adipose tissue contiguous to the periosteum of the underlying bone. These tumors are slow-growing, nontender masses that affect, almost exclusively, the diaphysis of the long bones of the upper and lower limbs. We hereby describe the CT characteristics with the correlative pathological findings in a rare case of parosteal lipoma of the rib. D 2003 Elsevier Inc. All rights reserved. Keywords: Parosteal lipoma; Rib; CT
1. Introduction Parosteal lipoma is a rare benign neoplasm composed mainly of mature adipose tissue that is contiguous to the underlying periosteal bone [1]. This neoplasm comprises 0.3% of all lipomas, and typically the most common location involved are the femur, proximal radius, humerus, tibia, clavicle and pelvis [2,3]. To the best of our knowledge, of the approximately 150 cases of parosteal lipoma reported in the literature, only 1 case has been previously described of parosteal lipoma of the rib [4]. We hereby describe the CT characteristics with the correlative pathologic findings in an exceedingly rare case of parosteal lipoma of the rib.
Clinical examination revealed a hard, nontender mass at the level of the right posterior fourth rib. Past medical history was unremarkable. On admission, a CT scan (Fig. 1) was obtained that showed a well-defined nonhomogeneous lobulated mass of fat attenuation attached to the lateral aspect of the right posterior fourth rib with the presence of a bony density arborisation within it and no evidence of inflammation or invasion of the adjacent muscles. The
2. Case report A 60-year-old man was admitted to our hospital with a 4-month history of progressive painful palpable mass at the level of the right posterior upper chest, which in the 3 weeks prior to admission had become more constant and intense.
* Corresponding author. Via Manzoni 214/0, Parco Flory, Isolato 4, Apt. 1, Napoli, Italy. Tel.: +39-81-5757370; fax: +39-81-5457081. E-mail address: [email protected] (M. Imbriaco). 0899-7071/03/$ – see front matter D 2003 Elsevier Inc. All rights reserved. doi:10.1016/S0899-7071(03)00010-X
Fig. 1. CT scan showing a well-defined lobulated mass of fat attenuation attached to the lateral aspect of the right posterior fourth rib with the presence of a bony arborisation within it.
436
M. Imbriaco et al. / Journal of Clinical Imaging 27 (2003) 435–437
Fig. 2. Gross specimen showing a 5 3.5 mass with a lobulated fatty appearance attached to the rib.
presence of 60 and 100 Hounsfield Unit throughout the lesion confirmed that the mass was mainly composed of adipose tissue with only thin fibrous septa within it. Subsequently, the patient underwent en bloc resection of the mass and of the right fourth rib. The specimen was formalinfixed and paraffin-embedded. A total of 5-m-thick sections were obtained for histological examination and were stained with hematoxylin and eosin. Gross pathologic inspection of the lesion showed an encapsulated, circumscribed rounded mass of 5 3.5 cm in size, firm, with pushing margins. In addition, it showed a lobulated cut surface, yellowish, of adipose appearance, with solid whitish and translucent areas (Fig. 2). Microscopically, the lesion was circumscribed by a thin fibrous capsule and mainly constituted by mature adipose tissue. Interspersed islands of metaplastic bone and cartilage were observed in this tissue. Adipocytes were benign without evidence of atypias or pleomorphism (Figs. 3 and 4). Mitosis or necrosis were not appreciated.
Fig. 3. Histopathologic specimen showing mature adipose tissue containing areas of bone differentiation and small vessels (hematoxylin and eosin 100 ).
Fig. 4. High power view showing areas of condroid differentiation. All the tissues are well-differentiated without evidence of atypias or mitosis (hematoxylin and eosin 400 ).
The final diagnosis was consistent with parosteal lipoma of the rib. After the surgical excision of the mass, the patient had an uneventful postoperative course with no evidence of local recurrence 26 months after surgery.
3. Discussion Parosteal lipoma are rare and usually asymptomatic benign lesions found by definition in close or direct apposition to bone, representing 0– 3% of all lipomas [2]. Parostal, rather than periosteal lipoma, is the preferred terminology since the fat cells are not found in the periosteum itself [2]. These tumors commonly affect adults in the fifth decade of life, with range of 3 –84 years, without predominance of sex. Since their original description by Seerig in 1836, various reviews in the English literature regarding this rare entity have been published over the years [5]. The majority of these lesions are located adjacent to the long bones and especially to the femur (in approximately one-third of the cases) [2]. The most common presenting symptom is that of a slow-growing, large, nontender, immobile mass not fixed to the skin. Occasionally, disturbances in motor and sensory function of adjacent nerves may occur due to local pressure, resulting in muscle atrophy [6]. Parosteal lipoma may be large enough to cause limitation of joint motion or to compress a vital structure, such as an artery, nerve or lymphatics. In addition, these lesions may vary in size, measuring up to 18 cm in maximal dimension, although they usually maintain an indolent growth pattern. The treatment of choice is surgical excision. Pathologically, a parosteal lipoma is circumscribed by a thin, fibrous capsule. The multilobulated mass has a broad base attachment to the underlying bone [7]. Occasionally, a cartilage cap covers the bony trabeculae, yielding an osteo-
M. Imbriaco et al. / Journal of Clinical Imaging 27 (2003) 435–437
chondromatous appearance. Microscopically, the fat cells of a parosteal lipoma appear histochemically identical to adipocites found in the subcutaneous tissues [8,9]. Islands of calcifications or bone may occur within the lipoma. These islands have been attributed to metaplasia of preexisting mesenchymal cells. There is no indication to date that this tumor undergoes malignant degeneration, although minimal cellular pleomorphism may occasionally occur. Radiographically, the most characteristic feature demonstrates a well-defined area of lucency adjacent to the cortical bone commonly associated with reactive changes in the underlying cortex. In particular, reactive changes of the underlying bone include focal cortical hyperostosis and osseous bowing or a shallow erosion of the outer surface of the subjacent bone cortex [10]. Prior authors have attributed these cortical erosions to long-standing pressure on the cortex by the soft tissue mass. On CT scan, parosteal lipomas usually present as welldefined mass almost entirely composed of mature adipose tissue, with an osseous excrescence within it and/or erosion at the attachment of the soft-tissue mass to the subjacent cortex. As in the case presented, the axial CT images are useful to define the relationship of the mass with the adjacent bone and can help to exclude a malignant process. In particular, liposarcoma may have a component of mature fat, but unlike lipomas they are poorly defined and heterogeneous and contain confluent soft-tissue densities (as opposed to the thin fibrous septa of a lipoma). In addition, liposarcomas may invade adjacent structures with possible distant metastasis [11]. Rarely, benign atypical lipomas may exist having large areas of dense collagen and giant cells [12]. In these cases, a biopsy would be necessary to establish the benign or malignant nature of the lesion. Multiplanar reconstruction CT images are helpful in evaluating the extent of the tumor and the relationship of the bone excrescence to the cortex of the adjacent bone and to the surrounding, uninvolved but possibly displaced structures. CT scan can also confirm the indolent nature of this lesion
437
showing mechanical displacement rather than invasion of the adjacent structures. In summary, we have described a rare case of parosteal lipoma of the rib with CT and pathologic correlation.
Acknowledgments The authors sincerely thank Graciana Diez-Roux for critically reviewing this paper and Mrs. Carmela Imparato for editing the manuscript.
References [1] Murphey MD, Johnson DL, Bhatia PS, Neff JR, Rosenthal HG, Walker CW. Parosteal lipoma: MR imaging characteristics. AJR Am J Roentgenol 1994;162:105 – 10. [2] Fleming RJ, Alpert M, Garcia A. Parostal lipoma. AJR Am J Roentgenol 1962;87:1075 – 84. [3] Bui-Mansfield LT, Myers CP, Chew FS. Parosteal lipoma of the fibula. AJR Am J Roentgenol 2000;174:1698. [4] Fiorentino L, Rossi G, Ruggiero C, Valli R, Gusolfino D, Massimiano M, Losi L, Barbolini G. Parosteal lipoma of the rib: report of a case. Pathologica 2001;93:668 – 71. [5] Kawashima A, Magid D, Fishman EK, Hruban RH, Ney DR. Parosteal ossifying lipoma: CT and MR findings. J Comput Assist Tomogr 1993;17:147 – 50. [6] Kim JY, Jung SL, Pak YH, Kang YK. Parostal lipoma with hyperostosis. Eur Radiol 1999;9:1810 – 2. [7] Yu JS, Weis L, Becker W. MR imaging of a parosteal lipoma. Clin Imaging 2000;24:15 – 8. [8] Kransdorf MJ, Moser RP, Mesi JM, Meyer CA. Fat-containing soft tissue masses of the extremities. Radiographics 1991;11:81 – 106. [9] Miller MD, Ragsdale BD, Sweet DE. Parosteal lipoma: a new perspective. Pathology 1992;24:132 – 9. [10] Demos TC, Bruno E, Armin A, Dobozi WR. Parosteal lipoma with enlarging osteochondroma. AJR Am J Roentgenol 1984;143:365 – 6. [11] Munk PL, Lee MJ, Janzen DL, Connel DG, Logan PM, Poon PY, Bainbridge TC. Lipoma and liposarcoma: evaluation using CT and MR imaging. AJR Am J Roentgenol 1997;169:589 – 94. [12] Bush CH, Spanier SS, Gillespy T. Imaging of atypical lipomas of the extremities: report of three cases. Skeletal Radiol 1988;17:472 – 5.