We report 25 cases of a peculiar sclerosing epithelioid variant of fibrosacroma (SEF) simulating an infiltrating carcinoma. The tumors occurred primarily in the deep muscuature and were frequently associated with the adacent ascia or periosteum. The patients' ages were 14 to 87 years (median, 45). Fourteen were male and 11 female. The tumors were located in the lower extremities and limb girdles (12 cases), trunk (9), upper limb girdles (2), and neck (2). They measured 2 to 14.5 cm in greatest dimension (median size, 7cm) and were gray to white and firm. Histologically, the lesions were characterized by a proliferation of rather uniform, small, slightly angulated, round to ovoid epithelioid cells with sparse, often clear cytoplasm arranged in distinct nests and cords. In all cases there was prominent hyaline sclerosis, sometimes reminiscent of osteoid or cartilage and foci of conventional fibrosarcoma. Occasional myxoid zones with cyst formation and foci of hyaline cartilage, calcification, and metaplastic bone were also seen. Mitotic figures were generally scarce. Vimentin was detected in 13 of 14 cases, epithelial membrane antigen in seven, S100 protein in four, and neuron-specific enolase in two. Cytokeratins were detected with AE1/AE3 and CAM 5.2 in two cases. Leukocyte common antigen. CD68 antigen, HMB45, desmin, and alpha;-smooth muscle actin were negative in all cases. In 13 of 14 cases, 75percnt; or more of the cells stained for proliferating cell nuclear antigen (PCNA). K167 immunostaining with MIB showed low proliferative activity in all cases, averaiging 5percnt; of tumor cells or less. In all cases, p53 was detected by immunohistochemical methods; bel-2, an antiapoptosis marker, was detected in more than 90percnt; of the cells in 11 of 12 cases. Ultrastructurally, both the epithelioid and spindled tumor cells had features of fibroblasts. Follow-up in 16 cases ranging from 13 months to 17 years 3 months (median, 11 years 4 months) revealed persistent disease or local recurrences in 53percnt; of patients and metastases in 43percnt;. The metastases were to the lungs (4 cases), skeleton (3), chest wall/pleura (3), pericardium (1), and brain (1). Four patients died of disease, four were alive with disease, two were known to be alive but disease status unknown, and six had no evidence of further disease at last follow-up. The data suggest that SEF is a relatively low-grade fibrosarcoma; yet it is fully malignant despite the presence of histologically benign-appearing foci. The proliferation markers PCNA and K67 did not correlate with prognosis. The histologic differential diagnosis is broad and includes infiltrating carcinoma and, to a lesser extent, sclerosing lymphoma, synovial sarcoma, and a variety of other sarcomas in addition to benign fibroblastic proliferations. Recognition of SEF is important for prognostic and therapeutic reasons.
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