Primary neuroendocrine carcinoma of the skin with an unusual follicular lymphocytic infiltrate of the dermis.

Primary neuroendocrine carcinoma of the skin (PNECS) is a rare cutaneous tumor occurring predominantly on sun-exposed skin of elderly people. This histomorphological appearance of this aggressive tumor can be highly variable depending on the predominating growth pattern. We present an unusual case of PNECS: the tumor masked by a dense lymphoid infiltrate with a well-formed follicular growth pattern. In these cases of PNECS, the differential diagnosis must be extended to lymphoid neoplasms as well as lymphoepithelial neoplasms.