Psoriasis on tumor

Indicators of the relative contribution of epidermis and dermis to the pathogenesis of psoriasis may be obtained from clinical observation. We studied a case of clinically characteristic and histologically identifiable plaque of chronic psoriasis occurring over transitional cell carcinoma metastatic to the dermis. The tumor substantially replaced the usual fibrous structure of the dermis, showing that a normally structured dermis is not requisite for the presence of psoriasis.