Melanocytic naevi and basal cell carcinoma: is there an association?

Background Melanoma and basal cell carcinoma (BCC) affect similar body sites and share a complex relationship with sun exposure. Objective To establish the existence and magnitude of association between melanocytic naevi, the strongest predictors of melanoma, and BCC to give possible insights into shared pathways of solar ultraviolet tumourigenesis. Methods In a community‐based longitudinal Australian study, detailed information was collected about sun sensitivity, and dermatologists assessed skin colour and counted naevi on the forearms (1986) and back (1992). The BCC frequency and sites were prospectively monitored until 2007. Multivariate logistic regression was used to assess the association of naevi on the forearms or on the back with the development of BCC, adjusting for other risk factors. Results Of 1621 study participants in 1992, 1339 (average age 49) had complete follow‐up and 401 (30%) of these had 1202 histologically confirmed BCCs until 2007. After adjustment for age, gender, skin colour, naevi on the back and sun exposure, overall BCC risk increased significantly in those with forearm naevi (odds ratio: 1.5; 95% confidence intervals: 1.1–1.9). Risk of BCC specifically on the back was doubled in those with many (11 or more) forearm naevi compared with no forearm naevi (odds ratio: 2.4; 95% confidence interval: 1.1–4.8). Naevi on the back were not associated with subsequent basal cell carcinoma. Conclusions High naevus prevalence on the arms is associated with future BCC development.