Primary Sclerosing Epithelioid Fibrosarcoma of Bone

Abstract

Sclerosing epithelioid fibrosarcoma (SEF) is a rare, aggressive malignant neoplasm characterized by small nests and linear arrays of epithelioid cells embedded in a dense collagenous matrix. Very few primary SEFs of bone have been reported. Recognition is critical, as the dense extracellular collagenous matrix can be interpreted as osteoid, leading to misdiagnosis as-osteosarcoma. MUC4 and SATB2 are 2 recently characterized immunohistochemical markers for SEF and osteosarcoma, respectively. In reports to date, osteosarcomas are positive for SATB2 and negative for MUC4, whereas soft tissue SEFs have shown the opposite immunohistochemical profile (SATB2-/MUC4+). The purpose of this study was to characterize the clinicopathologic and immunohistochemical features of 8 primary SEFs of bone. The patients presented at a wide range of ages (25 to 73 y; median 52 y). Tumors mostly involved long bones of the extremities, with 3 cases involving the femur, 2 involving the ulna, and 1 involving the humerus. Other sites of involvement included the second rib (1) and the C6 vertebra (1). Follow-up information was available for 7 patients, 3 of whom developed metastases within 2 years of diagnosis. The other 4 patients were free of local recurrence or metastases at 1, 5, 12, and >84 months of follow-up, respectively. Radiographically, the tumors were predominantly lytic and poorly marginated. Histologically, 6 tumors showed pure SEF morphology, and 2 showed hybrid SEF/low-grade fibromyxoid sarcoma morphology. Focal dystrophic mineralization was seen in 1 case but was limited to areas of necrosis. None of the tumors showed the lace-like pattern of mineralization typical of osteosarcoma. The majority (6/8) of the tumors strongly expressed MUC4. SATB2 was negative in all but 1 case, which showed variable weak to moderate staining in ∼50% of nuclei. In general, the combination of morphology, MUC4 expression, and the absence of SATB2 expression was highly useful in arriving at the correct diagnosis.

Sclerosing Epithelioid Fibrosarcoma – A Rare Sacral Lesion and Literature Review

“…They were recently characterized as immunohistochemical markers for SEF and osteosarcoma, respectively [5]. The first marker is important to another entity that was essential to exclude, the low-grade fibromyxoid sarcoma (LGFMS).…”

“…Ultrastructurally shows fibroblastic or myofibroblastic differentiation [4]. Greater cytological atypia, and the epithelioid appearance can lead to an improper diagnosis of metastatic carcinoma [5]. This is particularly difficult to the diagnosis on visceral organs because of its rarity and its epithelioid appearance, closely mimicking carcinomas [18].…”

“…Those features were not specific. The typical image of SEF with bone involvement is predominantly lytic and poorly marginated [5,10]. Accordingly, the following mainly tumours were included in the differential diagnosis: osteosarcoma, liposarcoma, assorted mesenchymal neoplasms that may exhibit epithelioid appearances, metastatic carcinoma, sclerosing hematolymphoid tumours, and malignant melanoma.…”

“…It may resemble infiltrating carcinoma, sclerosing lymphoma, and other sarcomas [4,5], and it may contain areas of conventional fibrosarcoma or minor areas resembling a lowgrade fibromixosarcoma, with transition to higher-grade fibrosarcoma, especially in recurrent cases [18]. Ultrastructurally shows fibroblastic or myofibroblastic differentiation [4].…”

“…It's a rare mesenchymal neoplasm that has been classified as a low-grade sarcoma, which is nowadays considered an obsolete terminology, regarding its malignant behaviour [3]. With a median age of diagnosis between 50 and 60 years-old [4,5], only 10% of patients are younger than 20 years at the time of diagnosis. There is no gender predominance in the SEF [1,2].…”