Chondroid chordomas and low-grade chondrosarcomas of the craniospinal axis: An immunohistochemical analysis of 17 cases

The classification of cartilaginous neoplasms of the craniospinal axis is controversial. Indeed, the very existence of chondroid chordomas has recently been questioned. In an effort to clarify the direction of differentiation of cartilaginous neoplasms of this region, 17 neoplasms obtained from 17 patients with cartilaginous tumors of the craniospinal axis were examined by immunohistochemistry with a panel of antibodies. The panel included antibodies to cytokeratin (CK), epithelial membrane antigen (EMA), vimentin (VIM), S-100 protein, carcinoembryonic antigen (CEA), and type II collagen. Areas with cartilaginous differentiation were present in all 17 neoplasms. These areas were characterized by a matrix of amorphous blue ground substance with lacunae that contained enlarged and slightly atypical cells. This cartilaginous matrix stained strongly for type II collagen. Thirteen of the 17 neoplasms had a biphasic growth pattern in which areas with conventional chordoma were admixed with areas with cartilaginous differentiation. The cells within the cartilaginous components of these 13 neoplasms stained for CK (10 of 12 cases), EMA (10 of 13 cases), VIM (12 of 12 cases), S-100 protein (seven of 12 cases), and CEA (two of nine cases). Similarly, the conventional chordoma components of these same 13 neoplasms stained for CK (12 of 12 cases), EMA (13 of 13 cases), VIM (12 of 12 cases), S-100 protein (nine of 12 cases), and CEA (two of nine cases). The hyaline-appearing areas between the cords and sheets of cells of the conventional chordoma components of these 13 tumors also stained with type II collagen. These 13 tumors with both neoplastic cartilage and conventional chordoma were classified as chondroid chordomas. One of the 17 cases was composed entirely of neoplastic cartilage; however, the cells within the matrix of the cartilage of this neoplasm stained with the epithelial markers (CK and EMA). Based on the presence of epithelial differentiation within this otherwise cartilaginous neoplasm, it was also classified as a chondroid chordoma. In contrast, the remaining three cases without histologic evidence of chordoma differentiation did not stain for CK or EMA, but they did stain for S-100 protein (three of three cases) and VIM (three of three cases). These three tumors were therefore classified as chondrosarcomas. For purposes of comparison, 19 conventional chordomas without cartilage and 29 peripheral chondrosarcomas were also stained. The 19 conventional chordomas stained in a pattern similar to the conventional chordoma components of the chondroid chordomas, whereas the 29 peripheral chondrosarcomas stained in a pattern similar to the three chondrosarcomas of the craniospinal axis. These results suggest that chordomas can contain cartilage and are distinguishable from chondrosarcomas.