Department of Surgical Pathology, (Bone and Soft Tissues) Disease Management Group, Tata Memorial Hospital (TMH), Homi Bhabha National Institute (HBNI) University, Room Number 818, 8th Floor, Annex Building, Dr E.B. Road, Parel, 400012, Mumbai, India.
Division of Molecular Pathology and Translational Medicine, Tata Memorial Hospital (TMH), Homi Bhabha National Institute (HBNI) University, Parel, Mumbai, India.
Skeletal Radiol. 2021 Nov;50(11):2299-2307. doi: 10.1007/s00256-021-03829-1. Epub 2021 May 29.
A solitary fibrous tumor (SFT) is documented in several body sites. However, there are few reports on the radiological and corresponding histopathological, including immunohistochemical, features of SFT in the lower extremities. A 58-year-old male presented with a lump in his right thigh of 6 months duration. Plain radiograph revealed a soft tissue lesion in his right thigh, involving the adjacent mid-diaphysis and showing focal cortical thickening and calcification. Magnetic resonance imaging scans displayed two well-defined, T1-isointense and T2 heterogeneously hyperintense lesions, measuring together 15 cm in the intermuscular plane and the juxtacortical location along the mid-diaphyseal region of the right femur. Radiologically, the differential diagnoses considered were undifferentiated pleomorphic sarcoma and synovial sarcoma. Microscopic examination of the core biopsy and the resected tumor revealed a tumor composed of cells with oval to spindle-shaped nuclei in a variably collagenized stroma, including hyalinized blood vessels and focal dystrophic calcification. Mitotic figures were 4/10 high power fields. Immunohistochemically, the tumor cells were positive for CD34, BCL2, and STAT6. Diagnosis of malignant SFT was offered. The tumor displayed NAB2ex4-STAT6ex2 gene fusion on molecular testing. This constitutes a relatively uncommon case report of a large SFT in the thigh, including its radiological and pathological features, confirmed by STAT6 immunostaining. An SFT should be considered in cases of slow-growing, well-defined soft tissue tumors, which are isointense on T1 and heterogeneously hyperintense on T2-weighted sequences, and display calcification and cortical thickening of the adjacent bones. Various differential diagnoses and their treatment-related implications in such cases are discussed herewith.
孤立性纤维瘤（SFT）可见于多个部位。然而，关于下肢 SFT 的放射学和相应的组织病理学（包括免疫组织化学）特征的报道很少。一名 58 岁男性因右大腿肿块就诊，病程 6 个月。平片显示右大腿软组织病变，累及邻近骨干中段，呈局灶性皮质增厚和钙化。磁共振成像扫描显示两个界限清楚的 T1 等信号和 T2 不均匀高信号病变，在股骨干肌间平面和皮质旁位置共长 15cm。影像学上，鉴别诊断考虑为未分化多形性肉瘤和滑膜肉瘤。核心活检和切除肿瘤的显微镜检查显示肿瘤由具有不同胶原化基质的椭圆形至梭形核细胞组成，包括玻璃样血管和局灶性营养不良性钙化。有丝分裂象为 4/10 高倍视野。免疫组织化学显示肿瘤细胞 CD34、BCL2 和 STAT6 阳性。提供了恶性 SFT 的诊断。肿瘤在分子检测中显示 NAB2ex4-STAT6ex2 基因融合。这是一例罕见的大腿巨大 SFT 病例报告，包括其放射学和病理学特征，通过 STAT6 免疫组化得到证实。在 T1 等信号和 T2 加权序列不均匀高信号、伴邻近骨皮质增厚和钙化的缓慢生长、界限清楚的软组织肿瘤中应考虑 SFT。在此讨论了此类病例的各种鉴别诊断及其治疗相关意义。
