Mixed adenoneuroendocrine carcinoma of the ampulla of Vater: Case report Introduction: Mixed adenoneuroendocrine carcinomas (MANEC) are types of biphasic tumors, morphologically recognized in the presence of a neoplastic formation constituted simultaneously by glandular epithelium and neuroendocrine cells. Only 19 cases located in the ampulla of Vater have been reported in the literature. Within the gastrointestinal tract, these neoplasms predominate in the stomach or colon. Aim: Report a case of MANEC; review of the epidemiology, prognosis and treatment of these tumors. Materials and Method: Case presentation of a patient diagnosed with mixed adeno-neuroendocrine carcinoma of the ampullary region. Discussion: The clinical presentation, management and prognosis are similar to ampullary adenocarcinoma. These tumors are diagnosed with a histopathological examination of the resected specimen. Both components must be histologically malignant, and each of them must represent at least 30% of the lesion. Conclusion: MANEC of the ampulla are rare tumors worldwide, being this case the first reported in our institute.