High incidence of H‐ras oncogene mutations in squamous cell carcinoma of lip vermilion

Nine specimens of well‐differentiated squamous cell carcinoma of the lip vermilion have been analyzed for the pressence of H‐ras oncogene mutations, using the technique of hybridization with synthetic oligonucleotide probes on in vitro amplified tumour DNA. Five specimens harbored mutations: four in codon 12 and one in codon 13. This high incidence (55%) of mutated H‐ras genes suggests that their activation may play an important role in lip tumour development and may be connected to the exposure to chemical and/or physical carcinogens