[Sclerosing epithelioid fibrosarcoma]

Sclerosing epithelioid fibrosarcoma (SEF) was first described in 1995 and since then 39 cases have been reported. Here we describe 6 cases of SEF (3 in women and 3 in men). The patients aged from 22 to 79 years. The tumours were located in soft tissues of the extremities (in 3 cases in the lower, in 2 instances in the upper extremity) and of the trunk (in 1 case). The lesions were partially nodular, of gray-white colour, and hard in consistency. Histologically, they were composed of epithelioid round to ovoid small cells with a sparse cytoplasm and a very low mitotic activity. The tumour cells formed cords and alveoli or were scattered individually within a dense hyalinized collagenous stroma. The neoplasms also contained foci of conventional fibrosarcoma, necrosis, calcification, and metaplastic bone. On immunohistochemistry, the neoplastic cells were positive for vimentin. Two cases were immunoreactive for epithelial membrane antigen and one tumour also for cytokeratins. The proliferative activity, assessed by MIB 1 antibody (Ki-67), was detected in 1-6% of neoplastic cells in primary tumours. Follow-up information was available in 5 patients. In two cases, there were local recurrences and distant metastases (in the lungs, upper extremity, and mediastinum). One of these patients died of SEF. The differential diagnosis of this relatively low-grade fibrosarcoma is broad and includes, along with a variety of benign and malignant soft tissue lesions, infiltrating carcinoma, and, to a lesser extent, sclerosing lymphoma.