Objective: p63 can be expressed by a minority of adenocarcinomas. ΔNp63 (p40), isoform of p63, has recently been reported as more specific in lung squamous cell carcinoma (SCC) than p63, and it appears to be a more reliable marker for SCC. There is no comprehensive study on p40 expression in tumours of different histotypes. Method: 460 tumours of various hisotypes were studied, including tumours of stratified epithelium such as SCC (84 cases) of the skin, head/neck, lung, cervix, and oesophagus, urothelial carcinomas (18), cutaneous basal cell carcinomas (5), thymomas (20) and thymic carcinomas (5), adenocarcinomas (210) from multiple organs, germ cell tumours (25), brain tumours (17), lymphomas (14), and sarcomas (12). p40 immunostains were performed on tissue microarrays and staining extent was evaluated as focal (1-50 %) and diffuse (50-100 %). Results: All but one tumours of stratified epithelium diffusely expressed p40. The negative case represents spindle cell SCC. Other tumours except for basal/squamous component of two teratomas, one breast metaplastic carcinoma, and squamous component of 5 adenosquamous carcinomas were all negative for p40. Conclusion: p40 is specific in tumours of stratified epithelium and its sensitivity appears comparable to p63. p40 can serve as a marker for tumours of stratified epithelium. Objective: Although formaldehyde is the standard fixative used in routine histopathology, it is not considered an "ideal" fixative. Formaldehyde presents carcinogenic properties, a slow fixation and produces cross-links with proteins and nucleic acids. Formaldehyde-free fixatives are commercially available.