A case report of metastatic mixed adeno-neuroendocrine carcinoma of the anus presenting as anal pain

Mixed adeno-neuroendocrine carcinoma (MANEC) is a rare disease, and much of the available literature to date has consisted of case reports. A recent systematic review revealed heterogeneity in the data as not all reports documented treatment regimens and course of disease. The recent 2019 WHO update on neuroendocrine carcinoma nomenclature adds to the pre-existing classification system based on biologic activity, to better represent the spectrum...