Primary Cutaneous Carcinomas with Neuroendocrine Differentiation.

Neuroendocrine neoplasms are observed in multiple organs and are classified into well-differentiated neuroendocrine tumors/carcinoid or poorly differentiated high-grade neuroendocrine carcinoma. This present article aims to summarize the most important clinical, morphologic, immunohistochemical, and genetic features of skin tumors with neuroendocrine phenotype focusing on Merkel cell carcinoma, Wnt/betacatenin rosette-forming carcinoma, endocrine mucin-producing sweat gland carcinoma, and the related sweat gland carcinoma with neuroendocrine differentiation. We especially focused on diagnosis management of these tumor entities in current practice as well as differential diagnosis.