The p63 protein is a member of the p53 family, which also includes p73. At least 6 different transcripts of p63 derives from alternative splicing events and encodes proteins with two different N termini (TA and ∆N) and three different C termini (α, β and γ). The protein isotypes TAp63α, TAp63β, and TAp63γ contain the N-terminal transactivation (TA) domain, whereas the other three isotypes ∆Np63α, ∆Np63β, and ∆Np63γ, lack this domain, and when present in sufficient concentration act in a dominant-negative manner with respect to wild-type p63 and p53 protein. p63 is detected in prostate basal cells in normal prostate glands and PIN. However, it is negative in prostate adenocarcinoma. Thus p63 is useful as a differential marker for benign prostate glands and adenocarcinoma (negative marker). The combination of AMACR, 34βE12, and p63 may be useful for diagnosing PIN and small focus adenocarcinoma, especially in difficult cases and cases with limited tissues.