Prevalence of skin and other cancers in patients with psoriasis.

The prevalence of skin and internal malignancies was estimated from the general practitioners' notes of 2247 patients with psoriasis and 4494 age- and sex-matched controls. The prevalence of skin cancer in the psoriatics was 155% that of controls, but this was not significant at the 5% level. Subgroup analysis showed an increase in skin cancers in women (P < 0.05). There was no difference in the age of onset of skin cancers between psoriatics and controls and there was no evidence of a cumulative therapeutic risk. There was no difference in the prevalence of non-skin cancers between psoriatics and controls.