Neuroendocrine carcinoma of the skin in a young adult.

Neuroendocrine (Merkel cell) carcinoma of the skin is usually a tumor found in elderly individuals. Microscopically, the tumor is a small cell carcinoma that involves primarily the dermis. The dominant ultrastructural features are the presence of short cell processes containing small, dense-core, membrane-bound granules. The tumor is often locally aggressive, has the potential to metastasize to lymph nodes, and eventually causes death. The authors report a case of such a neoplasm that affected a 24-year-old man with congenital ectodermal dysplasia. It was associated with a concurrent basal cell carcinoma.