Chondroid
chordomas are cartilage-rich
neoplasms, most often located in the spheno-occipital region, that have a better prognosis than classic
chordomas. The immunohistochemical features of 19 classic and chondroid
chordomas were studied retrospectively using
avidin-
biotin-complex (ABC) immunoperoxidase histochemistry on
formalin-fixed,
paraffin-embedded tissue. Of the 19
tumors, all located in the spheno-occipital region, 5 exhibited predominantly chondroid morphologic features. The 14 classic
chordomas showed the following pattern of
antigen expression (percent of
tumors positive):
epithelial membrane antigen (EMA) 100%, AE 1/3 (a "cocktail" of
monoclonal antibodies directed against low and high molecular weight epidermal cytokeratins) 100%, DP
keratin (DPK) 100%,
vimentin 100%, S100 86%,
neuron specific enolase (NSE) 100%,
carcinoembryonic antigen (CEA) 57%, and HMB-45 (an anti-
melanoma-associated antibody) 57%. The five chondroid
chordomas exhibited the following pattern: EMA 0%, AE 1/3 0%, DPK 0%,
vimentin 100%, S100 100%, NSE 100%, CEA 0%, and HMB-45 0%. The focal, weak HMB-45 positivity (performed on the index case because of a clinical concern of metastatic
melanoma) seen in 57% of the classic
chordomas is a previously unreported finding. This finding suggests either that classic
chordomas are capable of HMB-45 expression or that this antibody has broader reactivity than previously recognized. The lack of
cytokeratin, EMA, and CEA expression by the chondroid
chordomas is similar to
chondrosarcomas as reported in the literature and dissimilar to the classic
chordoma group. These immunohistochemical findings suggest that chondroid
chordomas may more validly be classified as low grade
chondrosarcomas.