Congenital fibrosarcoma: a congenital fibrous histiocytoma.

Using immunoperoxidase PAP technique in 2 cases of congenital fibrosarcoma, a great number of cells showed positive stain for alpha-1-antitrypsin (A1AT) and alpha-1-antichymotrypsin (A1ACT), both considered to be good histiocytic markers. The ultrastructure in 1 case also provides evidence of histiocytic differentiation. These findings suggest that congenital fibrosarcomas are actually congenital fibrous histiocytomas and may explain the presence of inflammatory infiltrates as in some malignant fibrous histiocytomas.