A primary sclerosing epithelioid fibrosarcoma of the pubic bone, with evidence of divergent epithelial differentiation.

Sclerosing epithelioid fibrosarcoma (SEF) is a rare variant of fibrosarcoma, described initially by Meis-Kindblom et al. in 1995 (Meis-Kindblom JM, Kindblom L-G, Enzinger FM. Sclerosing epithelioid fibrosarcoma: a variant of fibrosarcoma simulating carcinoma. Am J Surg Pathol. 1995;19:979-993): more than 80 cases have been documented clinicopathologically since. Bone is a rare primary site for SEF, with only 2 cases so far reported. This paper documents the detailed clinical, histological, immunohistochemical, and ultrastructural features of a case occurring in the pubic bone of a 57-year-old diabetic woman presenting with a history of pain and compromised mobility involving her hip. Radiology revealed a destructive lesion in the right pubic bone. The lesion was resected, and 7 months postoperatively it recurred. The patient died following metastases to multiple bony sites and liver, some 4 years after the onset of symptoms. Histologically, the tumor was consistent with SEF, although it showed some anomalous immunostaining, which, however, is typical of the tumor (for example, for S-100 protein and epithelial membrane antigen). By electron microscopy, some rough endoplasmic reticulum was present, but also tonofibrils and desmosomes. The overall features were of an SEF with the ultrastructural but incomplete immunohistochemical evidence for divergent epithelial differentiation. The differential diagnosis of this tumor is discussed.