Merkel cell carcinoma and chronic arsenicism.

Arsenic is a well-documented human carcinogen. Bowen's disease, squamous cell carcinoma, and basal cell carcinoma are the most common skin cancers found in patients exposed to arsenic over the long term. Merkel cell carcinoma has been documented in Taiwanese patients who resided in an endemic area of black foot disease, another condition found in patients with chronic arsenicism. We collected all cases of Merkel cell carcinoma diagnosed at two medical centers in Taiwan (N = 11) to find a possible association between chronic arsenicism and Merkel cell carcinoma. In our study 6 of the 11 patients were residents of the endemic areas for chronic arsenicism.