A high-grade carcinoma with neuroendocrine differentiation. This category includes small cell carcinomas, large cell neuroendocrine carcinomas, and Merkel cell carcinomas and excludes neuroendocrine carcinomas that arise from the head and neck. The head and neck neuroendocrine carcinomas include well-differentiated, moderately-differentiated, and poorly-differentiated (high-grade) neuroendocrine carcinomas. [from
NCI]