Multiple keratoacanthomas and squamous cell carcinomas occurring at psoriatic treatment sites.

A report on four patients with psoriasis who have developed multiple keratoacanthomas and squamous cell carcinoma at the treatment sites is presented. Two other reports have appeared in the literature which link the development of keratoacanthoma with psoriasis and pustular psoriasis. Although a number of etiologic factors have been suspected for the development of these new growths, this presentation will further assess the specific roles that treatment measures may have played in these cases. Furthermore, the significance of impaired cellular immune defense mechanisms will be discussed.