CD9, caveolin 1 (CAV1), tumor rejection antigen 1 (gp96), exosomal miRNAs (e.g., miR-486-5p, miR-486-3p, and miR-10b-5p are only secreted by cancer cells) have diagnostic value in HNSCC, and increased expression of HSP90, miR-31, miR-21, and MALAT1 are biomarkers for OSCC. Here, CD9 is linked to cancer.