A case of a mixed adenoneuroendocrine tumor of the colon

Neuroendocrine cells often coexist with exocrine neoplasms of the gut and each component is normally present in a variable range. Despite this frequent association, mixed exocrine-neuroendocrine carcinomas are rare. This entity is known as adenoneuroendocrine carcinoma (MANEC) and each of its malignant components represents at least 30%. In contrast, there are only a few reports of another rare association of an adenoma and a well differentiated neuroendocrine tumor (NET) in the colon and rectum. The term mixed adenoneuroendocrine tumor (MANET) was suggested due to its indolent behavior and distinct morphological characteristics with mild to moderate nuclear atypia and low number of mitoses1. However, it is not included in the recent World Health Organization (WHO) classification of tumors of the digestive system.