A term that refers to the staging of a duodenal neuroendocrine tumor according to the American Joint Committee on Cancer, 8th edition. This staging system applies to well-differentiated neuroendocrine tumors of the duodenum. Carcinomas of the duodenum, including high-grade (grade 3), poorly differentiated neuroendocrine carcinomas are not included in this staging system. (from AJCC 8th Ed.) [from NCI]