Malignant disseminated porokeratosis.

A patient has been observed with a distinct form of disseminated porokeratosis. During the course of his disease, he developed changes in the porokeratosis lesions that included cellular atypia, dysplasia, and invasive squamous cell carcinoma. One of the squamous cell carcinomas produced regional and disseminated metastases, resulting in the death of the patient. Although malignancy has been previously described in the various types of porokeratosis, this is the first report of disseminated metastases and death in any form of this disease.