Using data from a national
skin cancer survey, we assessed the risk of basal cell and
squamous cell carcinoma among patients with
psoriasis compared with the general population. For both male and female psoriatic patients, the risk of
basal cell carcinoma was significantly elevated (relative risk = 2.2 and 1.7; p less than 0.05, both comparisons). The risk of
squamous cell carcinoma was not significantly or substantially different for persons with a history of
psoriasis compared with other persons (relative risk = 1.3; p greater than 0.05). The relative risk of basal cell
skin cancer among patients with
psoriasis was significantly higher even after stratification for factors associated with both
psoriasis and cutaneous
malignancy, which include fair complexion, exposure to
coal tar or pitch, and exposure to radiation. Contrary to long-standing beliefs, our findings support the hypothesis that even after allowing for possible greater exposures to cutaneous
carcinogens, the risk of nonmelanoma
skin cancer in patients with
psoriasis is at least as great as in the general population. Thus persons with
psoriasis who are treated with potential
carcinogens such as ultraviolet radiation, tar, and oral
methoxsalen photochemotherapy merit careful, long-term monitoring.