p40

p40 (ΔNp63) is a truncated, non‑transactivating isoform of p63 and functions as a highly specific nuclear marker of squamous, urothelial, and myoepithelial/basal cell differentiation. In IHC, it demonstrates strong nuclear staining and is more specific than p63 for squamous cell carcinoma particularly in the lung making it a recommended IHC in immunopanels for subtyping non-small cell lung carcinoma. p40 positivity supports squamous differentiation, while its absence helps exclude squamous lineage in favour of adenocarcinoma or other tumour types (1).

Recommended Controls

Criteria for acceptable staining is a nuclear staining pattern. The recommended controls to include are prostate tumour or SCC of the skin which is a high expressor, testes, which is negative or tonsil where the squamous epithelial cells will stain positive.

Expected staining pattern

Cervical SCC

Skin epithelium

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.