Neuroendocrine Carcinomas of the Larynx and Head and Neck: Challenges in Classification and Grading.

Primary neuroendocrine carcinomas (NECs) of the larynx and head and neck are an uncommon and heterogeneous group of neoplasms categorized by the 2017 WHO Classification of Head and Neck Tumors as: (a) well-differentiated (WD-NEC), (b) moderately-differentiated (MD-NEC), and (c) poorly-differentiated (PD-NEC) with small cell and large cell types. The classification incorporates elements of differentiation and grading and closely correlates to the 5-year disease specific survival of 100, 52.8, 19.3 and 15.3% for each diagnostic category. These survival rates are based on historical data limited by the previous lack of standard pathologic diagnostic criteria. The classification has de-emphasized the use of the terms "carcinoid" and "atypical carcinoid" as diagnostic categories. The adoption of uniform pathologic criteria for the classification of NECs of the head and neck should enable the design of high quality studies in order to understand the molecular alterations of these neoplasms.