SUMMARYBasal cell carcinoma (BCC) is the commonest malignant neoplasm in white people. We present a large UK casecontrol study in which conditional logistic regression analysis of age-matched and gender-matched data sets was used to compare, first, cases with controls (n=403) and second, patients having multiple BCC with those having a single BCC (n=278). Eye/hair colour, occupation, skin type, social class, tumour site at presentation and smoking history were assessed.Social class 1/2, skin type 1, red/blonde hair and blue/green eyes were all related to BCC risk, social class most strongly (odds ratio 2.36, P=0.007). Truncal site at presentation was a risk factor for the development of multiple BCC (odds ratio 4.03, P=0.002).These data support the view that genetically mediated differences in ultraviolet responsiveness are important in BCC, though the scale of their effect is small. They may be exploitable in primary and secondary prevention as well as giving insights into pathogenesis. In particular, the fact that patients presenting with a truncal tumour are at increased risk of further BCC suggests that intermittent exposure in genetically predisposed individuals may contribute to a cancer susceptibility syndrome.

Allelism in the glutathione S-transferase, GSTM3 gene has been identified using PCR with specific primers to exon 6/exon 7. Sequencing showed the mutant GSTM3*B allele to have a three-base deletion in intron 6 with a frequency of 0.158. The mutation generates a recognition sequence, 5'-AAGATA-3', for the negative transcription factor YY1. GSTM3*B was significantly associated with GSTM1*A.