Atypical fibroxanthoma: two unusual variants.

Two unusual fibroxanthomas were studied by light microscopy. The first case contained numerous osteoclast-like cells and resembled malignant giant cell tumour of soft tissues, a variant of malignant fibrous histiocytoma. Osteoclast-like giant cells were negative for lysozyme and alpha-1-antitrypsin. The second case contained areas of chondroid differentiation which resembled chondrosarcoma. Tumour cells within the cartilaginous areas were positive for S100 protein.