It is clear that moles are a major risk factor for melanoma. Over the past nine years we have counted and mapped moles in over 600 pairs of Brisbane 12-year old twins and have followed up more half of them so far at age 14; we have also examined over 150 of their siblings. Analysis suggests very substantial genetic determination of mole count (>90 %) and a major role for the familial melanoma gene CDKN2A in the etiology of flat moles, but not of raised ones. We are in the process of linkage disequilibrium mapping in the p16 gene region on chromosome 9p to try and identify the genes responsible.
(N.G. Martin, A.C. Green, N.K. Hayward, D. Duffy, A. Eldridge, M. Grace, G. Zhu)