In two cases of thymic carcinoma (both squamous cell carcinomas) with homozygous deletion of CDKN2A, mTAP expression was lost; in a lymphoepithelial carcinoma with homozygous deletion of CDKN2A, mTAP was expressed. The gene discussed is CDKN2A; the disease is nasopharyngeal type undifferentiated carcinoma.