Background: The p63 transcription factor is a p53 homologue; however, its role in development and oncogenesis is more unambiguous than that of p53. TP63 encodes a variety of N-and C-terminal isoforms with different expression patterns and functions. The most frequently studied are N-terminal variants ΔNp63 (p40) and TAp63. p40 is a characteristic basal or myopithelial cell marker of stratified epithelium and it partakes in the regulation of proliferation and differentiation. The TAp63 isoform is more expressed in the suprabasal cell layer but is also expressed in primary oocytes, lymphocytes and stromal cells. It induces apoptosis and plays a role in the maintenance of genome integrity. The role of each isoform differs also in tumor progression. p40 is generally considered to behave as an oncoprotein in the regulation of cancer stem cells, while TAp63 expression is associated with a better prognosis. Aim: Nuclear expression of p63 is a widely used as a diagnostic marker in the clinical pathology of a spectrum of malignancies, mostly lung squamous cell carcinomas and urogenital tract carcinomas; however, it also used during examination of breast (BC) and prostate carcinoma bioptic samples. However, cytoplasmic or extracellular p63 expression is observed in neoplastic cells when the 4A4 antibody is used. This mini-review briefly summarizes the possibilities and pitfalls of p63 usage, particularly when it is used in bioptic diagnostics of BC and prostate carcinoma and highlights the potential applications of isoform specific p40 and TAp63 antibodies. It also describes other clinical usages of p63, for instance in the histogenetical classification of tumors.