Etiological differences between subtypes of cutaneous malignant melanoma: Western Canada Melanoma Study.

From newly incident cases in Western Canada, 415 patients with superficial spreading melanoma (SSM), 128 with nodular melanoma (NM), and 56 with lentigo maligna melanoma (LMM) were interviewed, with age- and sex-matched controls chosen from the general population. The associations of these 3 subtypes with pigmentation, skin reaction to sun, different types of sun exposure, sunburn, and suntan were assessed. Compared to the other types, LMM occurred in older patients, and 75% of lesions occurred on the head and neck: It was less strongly related to pigmentation factors, intermittent sun exposure, and skin reaction to sun. The associations of SSM and NM with pigmentation, chronic sun exposure, skin reaction, and suntan were very similar: Both were associated with intermittent sun exposure, but SSM was more strongly related to vacation exposures than was NM. These results were compared with those from a similar Australian study. While LMM appears different in its etiology from SSM and NM, there is no strong evidence of major etiological differences between SSM and NM.