TP53, a gene located on chromosome 17p13, encodes a nuclear protein (p53) involved in cell cycle regulation. This protein degrades in 20 minutes. However, the inactivated gene can produce a protein with a half-life 4-20 times longer than that of the wild type; it can be demonstrated by immunohistochemistry. Unfortunately, all the antibodies recognize both proteins, and the determination of a cutoff in the percentage of positive nuclei is required for the detection of cases with correlation of the TP53 mutation. In urologic tumors, p53 overexpression determination can be diagnostic help in low grade superficial bladder cancer, in cases of cystectomy and pN0, and in penile cancer without clinically involved lymph nodes. It does not seem useful in renal cell carcinoma or testicular germ cell tumors, and its utility is limited in prostate carcinoma.