Chondroblastoma and chondromyxoid fibroma (CMF) has been investigated in numerous histological studies, but its biological nature and histogenetic origin are still a matter of debate. We evaluated the expression of type II collagen, S100A2, S100B, and osteocalcin to study the matrix biochemistry and phenotype of the neoplastic cells in these tumors. Immunohistochemically, the expression of type II collagen was diffuse in 15 cases (75%) among total 20 chondroblastomas and 12 (85.7%) among total 14 CMFs. The expression of S100B was also diffuse in all cases (100%) of chondroblastomas and 12 cases (85.7%) of CMFs. We were able to obtain the expression of S100A2, focally. The expression of osteocalcin was focally noted in 18 cases (90%) of chondroblastomas and 8 cases (57.1%) of CMFs. In conclusion, our data support that chondroblastoma and CMF are a distinct tumor entity with the basic expression of chondroid markers. But these tumors also show histologic diversity with focal co-expression of osteoid markers.

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