- Email: [email protected]
Intramuscular Low-grade Fibromyxoid Sarcoma: A Case Report
INTRAMUSCULAR LOW-GRADE FIBROMYXOID SARCOMA: A CASE REPORT Kuo-Sheng Liao,1 Wan-Ting Huang,1 Sheau-Fang Yang,1,2 Song-Hsiung Chien,3 Tsyh-Jyi Hsieh,4 Chee-Yin Chai,1,2 and Chun-Chieh Wu1 Departments of 1Pathology, 3Orthopedics and 4Medical Imaging, Kaohsiung Medical University Hospital, Kaohsiung Medical University, and 2 Department of Pathology, School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
Low-grade fibromyxoid sarcoma (LGFMS) is a rare neoplasm that commonly arises in the deep soft tissues of the lower extremities, particularly in the thigh. LGFMS occurs preferentially in young male adults. The microscopic appearance of LGFMS exhibits bland fibroblastic spindle cells with a whorled or linear arrangement in fibrous and myxoid areas. Although LGFMS has a deceptively benign histologic appearance, local recurrence and late metastases have frequently been reported. Diagnosis of LGFMS is still difficult because of its characteristic bland-looking histologic features that can be confused with other benign or low-grade fibromyxoid lesions. Although immunohistochemical staining can offer an overview of the differential diagnosis of myxoid tumors of soft tissue, it is sometimes limited for diagnosis of LGFMS. However, recent cytogenetic and molecular analyses have provided significant improvements in the diagnosis of LGFMS. Such analyses have demonstrated that most cases of LGFMS have a characteristic t(7,16) (q33;p11) translocation, resulting in the FUS-CREB3L2 fusion gene. We report a 29-year-old female who presented with a LGFMS located in the soleus muscle of her left lower leg. Preoperative imaging suggested the possibility of an intramuscular histiocytoma of the left soleus muscle. In conclusion, diagnosis of LGFMS can be challenging in routine practice in surgical pathology because of its bland-looking features. The immunohistochemical and ultrastructural findings were consistent with the fibroblastic properties of LGFMS. Cytogenetic and/or molecular genetic analyses can be used as ancillary diagnostic tools for LGFMS.
Key Words: fibromyxoid, FUS-CREB3L2, low-grade fibromyxoid sarcoma (Kaohsiung J Med Sci 2009;25:448–54)
Low-grade fibromyxoid sarcomas (LGFMS) are rare neoplasms that predominantly affect young adults and commonly arise in deep soft tissues of the lower extremities. LGFMS exhibit a deceptively benign
Received: Feb 2, 2009 Accepted: Mar 18, 2009 Address correspondence and reprint requests to: Dr Chun-Chieh Wu, Department of Pathology, Kaohsiung Medical University Hospital, 100 Tzyou 1st Road, Kaohsiung 807, Taiwan. E-mail: [email protected]
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histologic appearance. Local postsurgical recurrences are common, and late metastases have also been recorded. A diagnosis of LGFMS remains problematic because of its bland-looking histologic features that can potentially be confused with other benign or low-grade fibromyxoid lesions. Significant improvements have recently been made regarding the cytogenetic and molecular analyses and have shown that most LGFMS have a characteristic chromosomal abnormality, t(7,16) (q32–34;p11) or t(11,16) (p11;p11) translocation, resulting in FUS-CREB3L2 or FUS-CREB3L1 Kaohsiung J Med Sci August 2009 • Vol 25 • No 8 © 2009 Elsevier. All rights reserved.
Low-grade fibromyxoid sarcoma
fusions, respectively. Therefore, reverse transcriptasepolymerase chain reaction (RT-PCR) may be useful for differential diagnosis.
CASE PRESENTATION A 29-year-old female presented with a 2-month history of a painless mass in her left lower leg. Magnetic resonance imaging showed a well-circumscribed, intramuscular soft-tissue mass measuring 5.3 × 4.2 × 3.8 cm that was located in the soleus muscle. No peritumoral infiltrate in adjacent muscle was noted. The mass, with an intermediate heterogeneous signal intensity (SI), was visible on T1-weighted images (Figure 1A). Heterogeneous low-to-high SI with multiple nodules was seen on T2-weighted images. The mass showed heterogeneous enhancement on T1-weighted fatsuppressed images (Figure 1B) after intravenous injection of gadolinium, mainly in the corresponding T2-weighted hyperintense areas in the peripheral region of the mass. The tumor was removed with wide excision. The specimen consisted of an oval, well-circumscribed, gray-white, firm soft-tissue tumor, measuring 5.4 × 4.3 × 3.6 cm. The cut sections showed homogeneous gray-white appearance (Figure 2A). Histologically, the tumor had an admixture of heavily collagenized,
A
hypocellular zones and more cellular myxoid nodules (Figure 2B). The tumor cells were bland spindleshaped cells with a fibroblast pattern, arranged in a whorled or linear growth pattern (Figure 2C). The tumor cells had indistinct pale eosinophilic cytoplasm and spindle-shaped to ovoid-shaped nuclei. Nucleoli were absent or indistinct and mitoses were absent. The vasculature of the tumor consisted of arcades of small vessels and arteriole-sized vessels (Figure 2C). Under an electron microscope, the neoplastic cells were characterized by spindle-shaped or plump cells, with abundant cytoplasm, rich in well-developed rough endoplasmic reticulum cisternae containing an electrolucent granular material. The cells were surrounded by abundant extracellular matrix consisting of banded collagen fibers (Figure 2D). Immunohistochemically, the neoplastic cells were stained strongly and were diffusely positive for vimentin, bcl-2 and CD99 (Figure 3), but did not show immunoreactivity to smooth muscle actin (Figure 3), desmin, S-100 protein, cytokeratin, epithelial membrane antigen (EMA), CD34, CD68, or β-catenin. RT-PCR analysis disclosed the breakpoints in the fusion transcript in exon 6 of FUS and exon 5 of CREB3L2 (Figure 4). These findings indicated that the tumor was associated with FUS/ CREB3L2. Therefore, histopathological diagnosis of LGFMS was made. The patient had no evidence of local recurrence or metastases after 4 months of follow-up.
B
Figure 1. (A) Coronal T1-weighted magnetic resonance imaging shows a well-defined mass with heterogeneous low to high signal intensity in the soleus muscle. (B) Post-contrast coronal T1-weighted fat-suppressed magnetic resonance imaging shows enhanced components in the peripheral region of the mass. Kaohsiung J Med Sci August 2009 • Vol 25 • No 8
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DISCUSSION LGFMS was first recognized as an entity by Evans in 1980, when he described a deceptive fibromyxoid sarcoma arising in the deep soft tissue of two women with subsequent development of lung metastases [1]. In 1997, Lane et al reported a hyalinizing spindle cell tumor with giant rosettes, which proved to be a giant rosette-containing variant of LGFMS [2]. LGFMS is a rare neoplasm that commonly occurs in young to middle-aged adults. Males are more commonly affected than females. LGFMS usually arises in the deep soft tissue of the lower extremity, particularly the thigh, but may occur in other deep soft tissues. LGFMS is frequently surrounded by skeletal muscle and typically presents as a painless deep soft tissue
mass. The mean tumor size (maximum dimension) at diagnosis is 9.5 cm [3]. LGFMS exhibits a heterogeneous multinodular appearance on magnetic resonance imaging with low to slightly high SI on T1-weighted images, heterogeneous low to high SI on T2-weighted images, and heterogeneous post-contrast enhancement [4]. The gross findings of LGFMS include a well circumscribed, oval to round mass with a thin, fibrous pseudocapsule. The cut surface shows whorled, white-gray, firm and fibrous consistency with homogenous appearance [1,2]. Microscopically, LGFMS typically shows an admixture of heavily collagenized, hypocellular zones and more cellular myxoid nodules. There is a proliferation of bland-appearance spindle tumor cells with a whorled or linear arrangement. The tumor cells
A
B
C
D
Figure 2. (A) Macroscopically, the tumor is an oval, well-circumscribed, gray-white and firm mass with a homogeneous cut surface. (B) Microscopically, the tumor is a well-circumscribed mass with an admixture of heavily collagenized and myxoid zones (hematoxylin & eosin; original magnification, 20×). (C) At higher magnification, the tumor cells are bland spindle-shaped cells with a fibroblast pattern that are arranged in a whorled or linear growth pattern, with myxoid changes and arcades of blood vessels (hematoxylin & eosin; original magnification, 100×). (D) Electron microscopic features include spindle-shaped or plump cells with abundant cytoplasm, rich in welldeveloped rough endoplasmic reticulum cisternae, containing an electrolucent granular material. The cells are surrounded by abundant extracellular matrix consisting of banded collagen fibers.
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Kaohsiung J Med Sci August 2009 • Vol 25 • No 8
Low-grade fibromyxoid sarcoma A
B
C
D
Figure 3. Immunohistochemistry of tumor cells reveal diffuse positivity for: (A) vimentin; (B) CD99; (C) Bcl-2. (D) Tumor cells are negative for smooth muscle actin.
A
Case 08-7141 A1 FUS-6A FUS-6A FUS-6A FUS-6A GADPH L1-5B L1-6B L2-5B L2-6B
B
FUS-exon 6
Breakpoint CREB3L2-exon 5
100 bp
Figure 4. (A) Detection of fusion transcripts in our case with low-grade fibromyxoid sarcoma by reverse transcriptase-polymerase chain reaction. Four sets of primers were used and detected: FUS-6A + CREB3L1-5B (lane 3), FUS-6A + CREB3L1-6B (lane 4), FUS-6A + CREB3L2-5B (lane 5) and FUS-6A + CREB3L2-6B (lane 6). Lane 1 = 100 base pair ladder; lane 2 = internal control (glyceraldehyde 3-phosphate dehydrogenase). (B) The nucleotide sequence shows and confirms the chimeric fusion transcripts of the FUS/CREB3L2(FUS-exon 6 + CREB3L2-exon 5) gene in our case with low-grade fibromyxoid sarcoma.
have poorly defined, pale eosinophilic cytoplasm and round- or ovoid-shaped nuclei. The vasculature of LGFMS consists of both arcades of small vessels, and arteriole-sized vessels with perivascular sclerosis. Nucleoli are usually absent or indistinct. Mitotic figures tend to be absent or rare. However, some cases have areas with increased cellularity and nuclear atypia, similar to that seen in typical fibrosarcomas of Kaohsiung J Med Sci August 2009 • Vol 25 • No 8
an intermediate grade [1,3,5,6]. Immunohistochemical staining has been reported by a number of authors and there are some conflicting results. LGFMS typically expresses only vimentin, which is consistent with fibroblastic differentiation. Some cases show focal positivity of smooth muscle actin, which is attributed to focal myofibroblastic differentiation. LGFMS were reported to be negative for desmin, S-100 protein, 451
K.S. Liao, W.T. Huang, S.F. Yang, et al
cytokeratin, EMA and CD34 [5,7]. However, a recent case series showed that most LGFMSs showed immunoreactivity to EMA, at least focally, CD99 and bcl-2 [8]. In our case, the tumor cells showed strong staining and were diffusely positive for vimentin, bcl-2 and CD99, but did not show immunoreactivity to smooth muscle actin, desmin, S-100 protein, cytokeratin, EMA, CD34, CD68 or β-catenin. Under an electron microscope, the neoplastic cells are characterized by spindle-shaped to plump cells, with abundant cytoplasm, rich in well-developed rough endoplasmic reticulum cisternae and contain electrolucent granular material. The cells are surrounded by abundant extracellular matrix consisting of banded collagen fibers. These results are consistent with a well-differentiated fibroblastic-type cell phenotype [9]. Diagnosis of LGFMS is still difficult because of its bland-looking histologic features that can potentially be confused with other benign or low-grade fibromyxoid lesions. However, significant improvements have recently been made because cytogenetic and molecular analyses showed that most LGFMS have a characteristic chromosomal abnormality, t(7;16) (q33;p11), which results in the FUS-CREB3L2 fusion gene. RT-PCR showed that the breakpoints in the fusion transcripts are always in exons 6 or 7 of FUS and in exon 5 of CREB3L2. The results indicated that FUS/CREB3L2 is specific for LGFMS and could therefore be used as a diagnostic marker [10–12]. In our case, RT-PCR analysis disclosed the breakpoints in the fusion transcript in exon 6 of FUS and exon 5 of CREB3L2. Therefore, the case was FUS/CREB3L2 positive. Microscopic differential diagnosis of LGFMS includes a number of entities that are characterized by proliferation of spindle cells with myxoid morphologies. There are several related neoplasms that are more commonly observed, including low-grade myxofibrosarcoma, perineurioma, neurofibroma, myxoid solitary fibrous tumor, and desmoid-type fibromatosis. Low-grade myxofibrosarcoma exhibits a more uniform myxoid stroma and more cellular atypia, but lacks areas of fibrous stroma or a whorled arrangement of tumor cells. Perineurioma may have fibrous and myxoid areas and is diffusely positive for EMA. Neurofibroma shows more slender wavy nuclei and expresses S-100. Myxoid solitary fibrous tumor is uniformly immunoreactive for CD34. Desmoid-type fibromatosis is characterized by clonal myofibroblast 452
proliferation and has somatic β-catenin or adenomatous polyposis coli gene mutations that lead to intranuclear accumulation of β-catenin. Desmoid-type fibromatosis also has a more fascicular architecture, and can resemble LGFMS. Recent studies have suggested that immunohistochemical staining for nuclear β-catenin can differentiate desmoid-type fibromatosis from LGFMS [13,14]. Satisfactory wide excision is the primary treatment for LGFMS. The role of chemotherapy and radiotherapy remains unknown because of the rarity of LGFMS. If widely excised, the local recurrence and metastatic rates are 10% and 5%, respectively. In our case, the patient had no evidence of local recurrence or metastases after 4 months of follow-up. In conclusion, a diagnosis of LGFMS can be challenging in a routine surgical pathology setting because of its bland-looking features. The immunohistochemical and ultrastructural findings were consistent with the fibroblastic nature of LGFMS. Cytogenetic and/or molecular genetic analyses could be used as an ancillary diagnostic tool for LGFMS.
ACKNOWLEDGMENTS The authors wish to thank Dr Hsuan-Ying Huang, Department of Pathology, Kaohsiung Medical Center, Chang Gung Memorial Hospital, Taiwan for his assistance, including reviewing the pathological slides.
REFERENCES 1.
2.
3. 4.
5.
Evans HL. Low-grade fibromyxoid sarcoma. A report of two metastasizing neoplasms having a deceptively benign appearance. Am J Clin Pathol 1987;88:615–9. Lane KL, Shannon RJ, Weiss SW. Hyalinizing spindle cell tumor with giant rosettes: a distinctive tumor closely resembling low-grade fibromyxoid sarcoma. Am J Surg Pathol 1997;21:1481–8. Evans HL. Low-grade fibromyxoid sarcoma. A report of 12 cases. Am J Surg Pathol 1993;17:595–600. Koh SH, Choe HS, Lee IJ, et al. Low-grade fibromyxoid sarcoma: ultrasound and magnetic resonance findings in two cases. Skeletal Radiol 2005;34:550–4. Folpe AL, Lane KL, Paull G, et al. Low-grade fibromyxoid sarcoma and hyalinizing spindle cell tumor with giant rosettes: a clinicopathologic study of 73 cases supporting their identity and assessing the impact of high-grade areas. Am J Surg Pathol 2000;24:1353–60. Kaohsiung J Med Sci August 2009 • Vol 25 • No 8
Low-grade fibromyxoid sarcoma 6.
7.
8.
9.
Goodlad JR, Mentzel T, Fletcher CD. Low grade fibromyxoid sarcoma: clinicopathological analysis of eleven new cases in support of a distinct entity. Histopathology 1995;26:229–37. Lindberg GM, Maitra A, Gokaslan ST, et al. Low grade fibromyxoid sarcoma: fine-needle aspiration cytology with histologic, cytogenetic, immunohistochemical, and ultrastructural correlation. Cancer 1999; 87:75–82. Guillou L, Benhattar J, Gengler C, et al. Translocationpositive low-grade fibromyxoid sarcoma: clinicopathologic and molecular analysis of a series expanding the morphologic spectrum and suggesting potential relationship to sclerosing epithelioid fibrosarcoma: a study from the French Sarcoma Group. Am J Surg Pathol 2007; 31:1387–402. Antonescu CR, Baren A. Spectrum of low-grade fibrosarcomas: a comparative ultrastructural analysis of low-grade myxofibrosarcoma and fibromyxoid sarcoma. Ultrastruct Pathol 2004;28:321–32.
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10. Bejarano PA, Padhya TA, Smith R, et al. Hyalinizing spindle cell tumor with giant rosettes—a soft tissue tumor with mesenchymal and neuroendocrine features. An immunohistochemical, ultrastructural, and cytogenetic analysis. Arch Pathol Lab Med 2000;124:1179–84. 11. Panagopoulos I, Storlazzi CT, Fletcher CD, et al. The chimeric FUS/CREB3l2 gene is specific for low-grade fibromyxoid sarcoma. Genes Chromosomes Cancer 2004; 40:218–28. 12. Reid R, de Silva MV, Paterson L, et al. Low-grade fibromyxoid sarcoma and hyalinizing spindle cell tumor with giant rosettes share a common t(7;16)(q34;p11) translocation. Am J Surg Pathol 2003;27:1229–36. 13. Bhattacharya B, Dilworth HP, Iacobuzio-Donahue C, et al. Nuclear beta-catenin expression distinguishes deep fibromatosis from other benign and malignant fibroblastic and myofibroblastic lesions. Am J Surg Pathol 2005;29:653–9. 14. Ng TL, Gown AM, Barry TS, et al. Nuclear beta-catenin in mesenchymal tumors. Mod Pathol 2005;18:68–74.
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肌肉內低度惡性纖維黏液樣肉瘤 — 病例報告 廖國生
1
黃婉婷
1
楊曉芳
1,2
簡松雄 1
3
謝賜吉 3
4
蔡志仁
1,2
吳俊杰
1
4
高雄醫學大學附設醫院 病理科 骨科 影像醫學部 2
高雄醫學大學 醫學院醫學系 病理學科
低度惡性纖維黏液樣肉瘤 (low-grade fibromyxoid sarcoma) 是罕見的深層軟組織 腫瘤，它通常發生在下肢，尤其好發於大腿。此種腫瘤好發於年輕男性，其顯微鏡下 的表現為在纖維狀和黏液樣的區域有分化良好的纖維母細胞樣之梭狀細胞以線形或漩 渦狀排列；雖然低度惡性纖維黏液樣肉瘤有偽良性的組織學表現，但是常局部復發和 甚至曾經有文獻報告晚期轉移的病例。要準確地診斷低度惡性纖維黏液樣肉瘤仍然是 困難的，由於它分化良好的組織學表現，因而與其它良性或低度惡性纖維黏液樣腫瘤 產生混淆；雖然免疫組織化學染色在診斷黏液樣腫瘤上常可以提供一個概述性鑑別診 斷，但是有時候在低度惡性纖維黏液樣肉瘤的診斷上仍然有所不足。最近的細胞遺傳 和分子分析在低度惡性纖維黏液樣肉瘤的診斷上有很大的改進，細胞遺傳和分子分析 顯示大部分的低度惡性纖維黏液樣肉瘤有獨特的第 7 對染色體與第 16 對染色體發生 轉 位〔t(7,16) (q33;p11) translocation〕 而 產 生 一 個 異 常 的 融 合 基 因 (FUS-
CREB3L2 )。我們報告的這一位 29 歲女性在她左下肢的比目魚肌內長出一個低度惡 性 纖 維 黏 液 樣 肉 瘤， 術 前 的 磁 共 振 影 像 懷 疑 可 能 是 左 比 目 魚 肌 內 的 組 織 細 胞 瘤 (histiocytoma)。結論，由於低度惡性纖維黏液樣肉瘤的良性外觀特徵，在外科病理 學的常規工作上要正確診斷一個低度惡性纖維黏液樣肉瘤可能是一件挑戰的任務，免 疫組織化學染色和超顯微結構發現低度惡性纖維黏液樣肉瘤的腫瘤細胞與纖維性母細 胞的性質一致，另外可以使用細胞遺傳和分子生物技術 1 分析當作診斷低度惡性纖維 黏液樣肉瘤的輔助診斷工具。 關鍵詞：纖維黏液樣，FUS-CREB3L2 ，低度惡性纖維黏液樣肉瘤 ( 高雄醫誌 2009;25:448–54)
收文日期：98 年 2 月 2 日 接受刊載：98 年 3 月 18 日 通訊作者：吳俊杰醫師 高雄醫學大學附設醫院病理科 高雄市 807 三民區自由一路 100 號 454
Kaohsiung J Med Sci August 2009 • Vol 25 • No 8
Low-grade fibromyxoid sarcoma (LGFMS) is a rare neoplasm that commonly arises in the deep soft tissues of the lower extremities, particularly in the thigh. LGFMS occurs preferentially in young male adults. The microscopic appearance of LGFMS exhibits bland fibroblastic spindle cells with a whorled or linear arrangement in fibrous and myxoid areas. Although LGFMS has a deceptively benign histologic appearance, local recurrence and late metastases have frequently been reported. Diagnosis of LGFMS is still difficult because of its characteristic bland-looking histologic features that can be confused with other benign or low-grade fibromyxoid lesions. Although immunohistochemical staining can offer an overview of the differential diagnosis of myxoid tumors of soft tissue, it is sometimes limited for diagnosis of LGFMS. However, recent cytogenetic and molecular analyses have provided significant improvements in the diagnosis of LGFMS. Such analyses have demonstrated that most cases of LGFMS have a characteristic t(7,16) (q33;p11) translocation, resulting in the FUS-CREB3L2 fusion gene. We report a 29-year-old female who presented with a LGFMS located in the soleus muscle of her left lower leg. Preoperative imaging suggested the possibility of an intramuscular histiocytoma of the left soleus muscle. In conclusion, diagnosis of LGFMS can be challenging in routine practice in surgical pathology because of its bland-looking features. The immunohistochemical and ultrastructural findings were consistent with the fibroblastic properties of LGFMS. Cytogenetic and/or molecular genetic analyses can be used as ancillary diagnostic tools for LGFMS.
Key Words: fibromyxoid, FUS-CREB3L2, low-grade fibromyxoid sarcoma (Kaohsiung J Med Sci 2009;25:448–54)
Low-grade fibromyxoid sarcomas (LGFMS) are rare neoplasms that predominantly affect young adults and commonly arise in deep soft tissues of the lower extremities. LGFMS exhibit a deceptively benign
Received: Feb 2, 2009 Accepted: Mar 18, 2009 Address correspondence and reprint requests to: Dr Chun-Chieh Wu, Department of Pathology, Kaohsiung Medical University Hospital, 100 Tzyou 1st Road, Kaohsiung 807, Taiwan. E-mail: [email protected]
448
histologic appearance. Local postsurgical recurrences are common, and late metastases have also been recorded. A diagnosis of LGFMS remains problematic because of its bland-looking histologic features that can potentially be confused with other benign or low-grade fibromyxoid lesions. Significant improvements have recently been made regarding the cytogenetic and molecular analyses and have shown that most LGFMS have a characteristic chromosomal abnormality, t(7,16) (q32–34;p11) or t(11,16) (p11;p11) translocation, resulting in FUS-CREB3L2 or FUS-CREB3L1 Kaohsiung J Med Sci August 2009 • Vol 25 • No 8 © 2009 Elsevier. All rights reserved.
Low-grade fibromyxoid sarcoma
fusions, respectively. Therefore, reverse transcriptasepolymerase chain reaction (RT-PCR) may be useful for differential diagnosis.
CASE PRESENTATION A 29-year-old female presented with a 2-month history of a painless mass in her left lower leg. Magnetic resonance imaging showed a well-circumscribed, intramuscular soft-tissue mass measuring 5.3 × 4.2 × 3.8 cm that was located in the soleus muscle. No peritumoral infiltrate in adjacent muscle was noted. The mass, with an intermediate heterogeneous signal intensity (SI), was visible on T1-weighted images (Figure 1A). Heterogeneous low-to-high SI with multiple nodules was seen on T2-weighted images. The mass showed heterogeneous enhancement on T1-weighted fatsuppressed images (Figure 1B) after intravenous injection of gadolinium, mainly in the corresponding T2-weighted hyperintense areas in the peripheral region of the mass. The tumor was removed with wide excision. The specimen consisted of an oval, well-circumscribed, gray-white, firm soft-tissue tumor, measuring 5.4 × 4.3 × 3.6 cm. The cut sections showed homogeneous gray-white appearance (Figure 2A). Histologically, the tumor had an admixture of heavily collagenized,
A
hypocellular zones and more cellular myxoid nodules (Figure 2B). The tumor cells were bland spindleshaped cells with a fibroblast pattern, arranged in a whorled or linear growth pattern (Figure 2C). The tumor cells had indistinct pale eosinophilic cytoplasm and spindle-shaped to ovoid-shaped nuclei. Nucleoli were absent or indistinct and mitoses were absent. The vasculature of the tumor consisted of arcades of small vessels and arteriole-sized vessels (Figure 2C). Under an electron microscope, the neoplastic cells were characterized by spindle-shaped or plump cells, with abundant cytoplasm, rich in well-developed rough endoplasmic reticulum cisternae containing an electrolucent granular material. The cells were surrounded by abundant extracellular matrix consisting of banded collagen fibers (Figure 2D). Immunohistochemically, the neoplastic cells were stained strongly and were diffusely positive for vimentin, bcl-2 and CD99 (Figure 3), but did not show immunoreactivity to smooth muscle actin (Figure 3), desmin, S-100 protein, cytokeratin, epithelial membrane antigen (EMA), CD34, CD68, or β-catenin. RT-PCR analysis disclosed the breakpoints in the fusion transcript in exon 6 of FUS and exon 5 of CREB3L2 (Figure 4). These findings indicated that the tumor was associated with FUS/ CREB3L2. Therefore, histopathological diagnosis of LGFMS was made. The patient had no evidence of local recurrence or metastases after 4 months of follow-up.
B
Figure 1. (A) Coronal T1-weighted magnetic resonance imaging shows a well-defined mass with heterogeneous low to high signal intensity in the soleus muscle. (B) Post-contrast coronal T1-weighted fat-suppressed magnetic resonance imaging shows enhanced components in the peripheral region of the mass. Kaohsiung J Med Sci August 2009 • Vol 25 • No 8
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K.S. Liao, W.T. Huang, S.F. Yang, et al
DISCUSSION LGFMS was first recognized as an entity by Evans in 1980, when he described a deceptive fibromyxoid sarcoma arising in the deep soft tissue of two women with subsequent development of lung metastases [1]. In 1997, Lane et al reported a hyalinizing spindle cell tumor with giant rosettes, which proved to be a giant rosette-containing variant of LGFMS [2]. LGFMS is a rare neoplasm that commonly occurs in young to middle-aged adults. Males are more commonly affected than females. LGFMS usually arises in the deep soft tissue of the lower extremity, particularly the thigh, but may occur in other deep soft tissues. LGFMS is frequently surrounded by skeletal muscle and typically presents as a painless deep soft tissue
mass. The mean tumor size (maximum dimension) at diagnosis is 9.5 cm [3]. LGFMS exhibits a heterogeneous multinodular appearance on magnetic resonance imaging with low to slightly high SI on T1-weighted images, heterogeneous low to high SI on T2-weighted images, and heterogeneous post-contrast enhancement [4]. The gross findings of LGFMS include a well circumscribed, oval to round mass with a thin, fibrous pseudocapsule. The cut surface shows whorled, white-gray, firm and fibrous consistency with homogenous appearance [1,2]. Microscopically, LGFMS typically shows an admixture of heavily collagenized, hypocellular zones and more cellular myxoid nodules. There is a proliferation of bland-appearance spindle tumor cells with a whorled or linear arrangement. The tumor cells
A
B
C
D
Figure 2. (A) Macroscopically, the tumor is an oval, well-circumscribed, gray-white and firm mass with a homogeneous cut surface. (B) Microscopically, the tumor is a well-circumscribed mass with an admixture of heavily collagenized and myxoid zones (hematoxylin & eosin; original magnification, 20×). (C) At higher magnification, the tumor cells are bland spindle-shaped cells with a fibroblast pattern that are arranged in a whorled or linear growth pattern, with myxoid changes and arcades of blood vessels (hematoxylin & eosin; original magnification, 100×). (D) Electron microscopic features include spindle-shaped or plump cells with abundant cytoplasm, rich in welldeveloped rough endoplasmic reticulum cisternae, containing an electrolucent granular material. The cells are surrounded by abundant extracellular matrix consisting of banded collagen fibers.
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Kaohsiung J Med Sci August 2009 • Vol 25 • No 8
Low-grade fibromyxoid sarcoma A
B
C
D
Figure 3. Immunohistochemistry of tumor cells reveal diffuse positivity for: (A) vimentin; (B) CD99; (C) Bcl-2. (D) Tumor cells are negative for smooth muscle actin.
A
Case 08-7141 A1 FUS-6A FUS-6A FUS-6A FUS-6A GADPH L1-5B L1-6B L2-5B L2-6B
B
FUS-exon 6
Breakpoint CREB3L2-exon 5
100 bp
Figure 4. (A) Detection of fusion transcripts in our case with low-grade fibromyxoid sarcoma by reverse transcriptase-polymerase chain reaction. Four sets of primers were used and detected: FUS-6A + CREB3L1-5B (lane 3), FUS-6A + CREB3L1-6B (lane 4), FUS-6A + CREB3L2-5B (lane 5) and FUS-6A + CREB3L2-6B (lane 6). Lane 1 = 100 base pair ladder; lane 2 = internal control (glyceraldehyde 3-phosphate dehydrogenase). (B) The nucleotide sequence shows and confirms the chimeric fusion transcripts of the FUS/CREB3L2(FUS-exon 6 + CREB3L2-exon 5) gene in our case with low-grade fibromyxoid sarcoma.
have poorly defined, pale eosinophilic cytoplasm and round- or ovoid-shaped nuclei. The vasculature of LGFMS consists of both arcades of small vessels, and arteriole-sized vessels with perivascular sclerosis. Nucleoli are usually absent or indistinct. Mitotic figures tend to be absent or rare. However, some cases have areas with increased cellularity and nuclear atypia, similar to that seen in typical fibrosarcomas of Kaohsiung J Med Sci August 2009 • Vol 25 • No 8
an intermediate grade [1,3,5,6]. Immunohistochemical staining has been reported by a number of authors and there are some conflicting results. LGFMS typically expresses only vimentin, which is consistent with fibroblastic differentiation. Some cases show focal positivity of smooth muscle actin, which is attributed to focal myofibroblastic differentiation. LGFMS were reported to be negative for desmin, S-100 protein, 451
K.S. Liao, W.T. Huang, S.F. Yang, et al
cytokeratin, EMA and CD34 [5,7]. However, a recent case series showed that most LGFMSs showed immunoreactivity to EMA, at least focally, CD99 and bcl-2 [8]. In our case, the tumor cells showed strong staining and were diffusely positive for vimentin, bcl-2 and CD99, but did not show immunoreactivity to smooth muscle actin, desmin, S-100 protein, cytokeratin, EMA, CD34, CD68 or β-catenin. Under an electron microscope, the neoplastic cells are characterized by spindle-shaped to plump cells, with abundant cytoplasm, rich in well-developed rough endoplasmic reticulum cisternae and contain electrolucent granular material. The cells are surrounded by abundant extracellular matrix consisting of banded collagen fibers. These results are consistent with a well-differentiated fibroblastic-type cell phenotype [9]. Diagnosis of LGFMS is still difficult because of its bland-looking histologic features that can potentially be confused with other benign or low-grade fibromyxoid lesions. However, significant improvements have recently been made because cytogenetic and molecular analyses showed that most LGFMS have a characteristic chromosomal abnormality, t(7;16) (q33;p11), which results in the FUS-CREB3L2 fusion gene. RT-PCR showed that the breakpoints in the fusion transcripts are always in exons 6 or 7 of FUS and in exon 5 of CREB3L2. The results indicated that FUS/CREB3L2 is specific for LGFMS and could therefore be used as a diagnostic marker [10–12]. In our case, RT-PCR analysis disclosed the breakpoints in the fusion transcript in exon 6 of FUS and exon 5 of CREB3L2. Therefore, the case was FUS/CREB3L2 positive. Microscopic differential diagnosis of LGFMS includes a number of entities that are characterized by proliferation of spindle cells with myxoid morphologies. There are several related neoplasms that are more commonly observed, including low-grade myxofibrosarcoma, perineurioma, neurofibroma, myxoid solitary fibrous tumor, and desmoid-type fibromatosis. Low-grade myxofibrosarcoma exhibits a more uniform myxoid stroma and more cellular atypia, but lacks areas of fibrous stroma or a whorled arrangement of tumor cells. Perineurioma may have fibrous and myxoid areas and is diffusely positive for EMA. Neurofibroma shows more slender wavy nuclei and expresses S-100. Myxoid solitary fibrous tumor is uniformly immunoreactive for CD34. Desmoid-type fibromatosis is characterized by clonal myofibroblast 452
proliferation and has somatic β-catenin or adenomatous polyposis coli gene mutations that lead to intranuclear accumulation of β-catenin. Desmoid-type fibromatosis also has a more fascicular architecture, and can resemble LGFMS. Recent studies have suggested that immunohistochemical staining for nuclear β-catenin can differentiate desmoid-type fibromatosis from LGFMS [13,14]. Satisfactory wide excision is the primary treatment for LGFMS. The role of chemotherapy and radiotherapy remains unknown because of the rarity of LGFMS. If widely excised, the local recurrence and metastatic rates are 10% and 5%, respectively. In our case, the patient had no evidence of local recurrence or metastases after 4 months of follow-up. In conclusion, a diagnosis of LGFMS can be challenging in a routine surgical pathology setting because of its bland-looking features. The immunohistochemical and ultrastructural findings were consistent with the fibroblastic nature of LGFMS. Cytogenetic and/or molecular genetic analyses could be used as an ancillary diagnostic tool for LGFMS.
ACKNOWLEDGMENTS The authors wish to thank Dr Hsuan-Ying Huang, Department of Pathology, Kaohsiung Medical Center, Chang Gung Memorial Hospital, Taiwan for his assistance, including reviewing the pathological slides.
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10. Bejarano PA, Padhya TA, Smith R, et al. Hyalinizing spindle cell tumor with giant rosettes—a soft tissue tumor with mesenchymal and neuroendocrine features. An immunohistochemical, ultrastructural, and cytogenetic analysis. Arch Pathol Lab Med 2000;124:1179–84. 11. Panagopoulos I, Storlazzi CT, Fletcher CD, et al. The chimeric FUS/CREB3l2 gene is specific for low-grade fibromyxoid sarcoma. Genes Chromosomes Cancer 2004; 40:218–28. 12. Reid R, de Silva MV, Paterson L, et al. Low-grade fibromyxoid sarcoma and hyalinizing spindle cell tumor with giant rosettes share a common t(7;16)(q34;p11) translocation. Am J Surg Pathol 2003;27:1229–36. 13. Bhattacharya B, Dilworth HP, Iacobuzio-Donahue C, et al. Nuclear beta-catenin expression distinguishes deep fibromatosis from other benign and malignant fibroblastic and myofibroblastic lesions. Am J Surg Pathol 2005;29:653–9. 14. Ng TL, Gown AM, Barry TS, et al. Nuclear beta-catenin in mesenchymal tumors. Mod Pathol 2005;18:68–74.
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肌肉內低度惡性纖維黏液樣肉瘤 — 病例報告 廖國生
1
黃婉婷
1
楊曉芳
1,2
簡松雄 1
3
謝賜吉 3
4
蔡志仁
1,2
吳俊杰
1
4
高雄醫學大學附設醫院 病理科 骨科 影像醫學部 2
高雄醫學大學 醫學院醫學系 病理學科
低度惡性纖維黏液樣肉瘤 (low-grade fibromyxoid sarcoma) 是罕見的深層軟組織 腫瘤，它通常發生在下肢，尤其好發於大腿。此種腫瘤好發於年輕男性，其顯微鏡下 的表現為在纖維狀和黏液樣的區域有分化良好的纖維母細胞樣之梭狀細胞以線形或漩 渦狀排列；雖然低度惡性纖維黏液樣肉瘤有偽良性的組織學表現，但是常局部復發和 甚至曾經有文獻報告晚期轉移的病例。要準確地診斷低度惡性纖維黏液樣肉瘤仍然是 困難的，由於它分化良好的組織學表現，因而與其它良性或低度惡性纖維黏液樣腫瘤 產生混淆；雖然免疫組織化學染色在診斷黏液樣腫瘤上常可以提供一個概述性鑑別診 斷，但是有時候在低度惡性纖維黏液樣肉瘤的診斷上仍然有所不足。最近的細胞遺傳 和分子分析在低度惡性纖維黏液樣肉瘤的診斷上有很大的改進，細胞遺傳和分子分析 顯示大部分的低度惡性纖維黏液樣肉瘤有獨特的第 7 對染色體與第 16 對染色體發生 轉 位〔t(7,16) (q33;p11) translocation〕 而 產 生 一 個 異 常 的 融 合 基 因 (FUS-
CREB3L2 )。我們報告的這一位 29 歲女性在她左下肢的比目魚肌內長出一個低度惡 性 纖 維 黏 液 樣 肉 瘤， 術 前 的 磁 共 振 影 像 懷 疑 可 能 是 左 比 目 魚 肌 內 的 組 織 細 胞 瘤 (histiocytoma)。結論，由於低度惡性纖維黏液樣肉瘤的良性外觀特徵，在外科病理 學的常規工作上要正確診斷一個低度惡性纖維黏液樣肉瘤可能是一件挑戰的任務，免 疫組織化學染色和超顯微結構發現低度惡性纖維黏液樣肉瘤的腫瘤細胞與纖維性母細 胞的性質一致，另外可以使用細胞遺傳和分子生物技術 1 分析當作診斷低度惡性纖維 黏液樣肉瘤的輔助診斷工具。 關鍵詞：纖維黏液樣，FUS-CREB3L2 ，低度惡性纖維黏液樣肉瘤 ( 高雄醫誌 2009;25:448–54)
收文日期：98 年 2 月 2 日 接受刊載：98 年 3 月 18 日 通訊作者：吳俊杰醫師 高雄醫學大學附設醫院病理科 高雄市 807 三民區自由一路 100 號 454
Kaohsiung J Med Sci August 2009 • Vol 25 • No 8