PTEN (Phosphatase And Tensin Homolog), which contains a tensin like domain as well as a catalytic domain, similar to that of the dual specificity protein tyrosine phosphatases, serves as a multi-functional tumor suppressor that is mutated in a large number of cancers at high frequency, including ccRCC (5, 6). The gene discussed is PTEN; the disease is nonpapillary renal cell carcinoma.