A neoplasm with neuroendocrine differentiation that arises from the rectum. It includes well differentiated neuroendocrine tumors (low and intermediate grade) and poorly differentiated neuroendocrine carcinomas (high grade). The disease is rectum neuroendocrine neoplasm (MONDO_0003646). Also known as: neuroendocrine neoplasm of rectum, neuroendocrine neoplasm of the rectum, rectal neuroendocrine neoplasm.