Mixed Adeno-Neuroendocrine Neoplasms: Two Cases, One Institution.

Epithelial tumors with neuroendocrine and nonendocrine components constitute the rare yet aggressive entity of neoplasms of the gastro-entero-pancreatic tract. These tumors were first named "mixed adeno-neuroendocrine carcinomas" (MANECs) by the World Health Organization in 2010 and in 2017 renamed "mixed neuroendocrine non-neuroendocrine neoplasms" (MiNENs). Combined adenocarcinoma and neuroendocrine carcinoma neoplasms are a rare occurrence within the gastrointestinal tract. In this report, we describe two separate cases of mixed rectal adeno-neuroendocrine carcinomas and their treatment. We describe two cases at one institution of mixed neuroendocrine non-neuroendocrine rectal neoplasms. Given the rarity of diagnosis and inconsistencies in both nomenclature and treatment recommendations in the literature, mixed adeno-neuroendocrine carcinoma epidemiology and prognosis are not yet fully understood. Future prospective trials with a focus in management of MiNENs will offer valuable insight into these rare mixed carcinomas.