Skin tumours in white South Africans. Part IV. Influence of occupation, sun sensitivity, colouring and associated skin tumours on the incidence of skin tumours.

Outdoor and industrial occupations in the southern Transvaal do not increase the incidence of any skin tumour excepting that of squamous cell carcinoma. However, they accelerate the onset of solar keratoses and squamous and basal cell carcinomas. A fair, sun-sensitive skin, red hair and blue eyes are more important factors predisposing towards the development of skin cancer. Unduly large numbers of seborrhoeic keratoses were found in association with polyps, and of intradermal naevi with both cavernous haemangiomas and lentigines. A high proportion of solar keratosis was found in both squamous cell carcinoma and Bowen's disease, and of basal cell carcinoma in superficial basal carcinoma, but the reverse associations were not significant.