A term that refers to the staging of ampulla of Vater cancer according to the American Joint Committee on Cancer, 8th edition. This staging system does not apply to well-differentiated neuroendocrine (carcinoid) tumors but does apply to high-grade neuroendocrine carcinomas, such as small cell carcinoma and large cell neuroendocrine carcinoma. (from AJCC 8th Ed.) [from NCI]