p53

p53 is a 53 kDa tumour‑suppressor protein encoded on chromosome 17p13, and its IHC staining pattern serves as a useful surrogate marker for underlying TP53 mutation status. In IHC p53 shows nuclear staining, either diffuse, strong overexpression or complete absence of staining this correlates strongly with pathogenic TP53 mutations, while heterogeneous low‑to‑intermediate nuclear staining suggests wild‑type protein. Because p53 regulates DNA repair, cell‑cycle arrest, and apoptosis, aberrant staining is seen in a wide range of malignancies and is particularly valuable in distinguishing high‑grade serous carcinoma (mutation pattern) from low‑grade serous tumours (wild‑type pattern), as well as in evaluating precursor lesions such as serous tubal intraepithelial carcinoma (1).

Recommended Controls

Criteria for acceptable staining is a nuclear staining pattern. It is recommended to include either tonsil, fallopian tube or appendix as a good in-house low expressor control, with a high expressor such as an ovarian tumour, to avoid any false negatives. P53 shows variability in the intensity of staining in normal tissue.

Expected staining pattern

Fallopian tube

Ovarian tumour

Disclaimer

These methods are intended as a guide only. Laboratories that wish to implement these methods should perform internal validation/verification prior to use. The RCPAQAP does not make any claim or warranty for the accuracy or performance of these methods.