Intrinsic neuroendocrine cells in the outer wall of the human pyriform recess

The extrinsic neural supply of the hypopharynx is well established. However, little is known about the intrinsic neurons and neuroendocrine cells (NECs) of the human hypopharynx that are under the influence of the extrinsic nerves. We aimed to identify and characterize such cell populations within the outer wall of the pyriform recess. We applied antibodies for neuron-specific enolase (NSE), calretinin (CR) and neurofilaments (NF) to autopsy samples from four donor cadavers. Within the lamina propria and the muscle layer of the pyriform recess outer wall, usually in perivascular areas, we found NSE-, CR- and NF-positive cells, mostly apolar, that were considered on a histological and immunohistochemical basis to be NECs. Although these cells have not, to our knowledge, been described previously in this anatomical location, their presence within the hypopharynx wall may explain the appearance of rare forms of local primary neuroendocrine carcinomas.