Loss of CDKN2A occurs in 10–15% of allhuman cancers and with greater frequency in histologies such as malignantperipheral nerve sheath tumors, glioblastoma (GBM), mesothelioma,urothelial carcinoma, esophageal squamous cell carcinoma, pancreaticadenocarcinoma, melanoma, nonsmall cell lung cancer, head and neckcancer, and cholangiocarcinoma.4−6 Due to its proximity to CDKN2A on chromosome 9p21, MTAP is frequentlycodeleted. The gene discussed is CDKN2A; the disease is urothelial carcinoma.