Congenital fibrosarcoma: presence of a histiocytic component.

We describe the histologic and ultrastructural appearance of a massive soft-tissue tumor in the left lower extremity of a newborn girl. In its clinical presentation and morphologic features, this tumor corresponded to the entity currently known as congenital fibrosarcoma. The variability of histologic conformation of these lesions is emphasized. Ultrastructural study disclosed many cells with the subcellular morphology of elements of the histiocytic-macrophagic series. Whether these cells are viewed as an integral part of the tumor or as a secondary feature, their presence in a congenital fibrosarcoma is of interest for understanding of biologic behaviour of these uncommon tumors.