Fusion of the FUS and ATF1 genes in a large, deep-seated angiomatoid fibrous histiocytoma

We report a case of a large, deep-seated, diagnostically difficult angiomatoid fibrous histiocytoma. The neoplastic cells were positive for vimentin, calponin, CD99, and, focally, for desmin and contained intertwining cytoplasmic processes joined by desmosomelike junctions. Fusion of codon 175 of the FUS gene to codon 110 of the ATF1 gene was detected by reverse transcription-polymerase chain reaction. Because identical fusion of the FUS and ATF1 genes has been recently reported in another case of angiomatoid fibrous histiocytoma, fusion of these genes may be characteristic for at least a subset of these tumors.