Extraskeletal chondroma with chondroblastic and granuloma-like elements.

A unique case of extraskeletal chondroma occurring in the right ring finger of a 51-year-old man is reported. The tumor, measuring 4.0 x 2.2 x 1.5 cm, consisted of chondroid, granuloma-like, and chondroblastic cell zones associated with fine calcification. Immunohistochemically, most of the tumor cells except for multinucleated giant cells were positive for vimentin. Cells positive for S-100 protein were scattered throughout the tumor, and cells positive for alpha-1 antichymotrypsin were observed in the chondroblastic cell zone and in the granuloma-like area. Ultrastructurally, the chondroblastic cells had a characteristic microvillous cell border.