The diagnosis of prostatic adenocarcinoma and the differentiation between it and its mimickers, especially in needle biopsy, may be challenging.In this study we examined the expression of p63 in atypical small acinar proliferation (ASAP) and prostatic adenocarcinoma cases.Prostatic adenocarcinoma cases showed negative p63 expression.The diagnosis of atypical small acinar proliferation (ASAP) cases was reevaluated according p63 expression. Cases that showed negative p63 staining proved to be malignant and cases that showed positive staining proved to be benign and the was shifted to one of the benign mimickers of prostatic adenocarcinoma.P63 proved to be beneficial in determining the nature of ASAP cases and in achieving a definitive diagnosis for these cases.