Sclerosing epithelioid fibrosarcoma primary of the bone.

Sclerosing epithelioid fibrosarcoma (SEF) is an uncommon tumor originally described in soft tissues. We report a case of SEF primary of the left iliac bone in a 42-year-old woman. The tumor was grossly well circumscribed. The histologic examination disclosed a hypocellular neoplasm with densely hyalinized stroma. It was composed predominantly of small-to-moderate-sized round-to-ovoid cells, relatively uniform, often with clear cytoplasm, and arranged in nest, cord, and strand patterns. Because the distinctive morphologic patterns and the immunohistochemical profile of this entity may be mistaken for many different tumors, we here emphasize the differential diagnostic problems of this variant of fibrosarcoma. To our knowledge, this is the first tumor of this kind described in the bone.