Fig. 1.

Human chordoma tissue sections were stained with monoclonal antibodies directed against the HLA class I antigen components: HLA-A heavy chain, HLA-B/C heavy chain, and β₂m. These representative sections demonstrate staining intensity (strongly positive, weakly positive, and negative). Scoring was performed independently by at least two investigators and was confirmed independently by a senior bone and soft tissue pathologist; β₂m = beta-2-microglobulin.