Ampullary Neuroendocrine Neoplasm: Clinicopathological Characteristics and Novel Endoscopic Entity

Abstract

Background: Neuroendocrine neoplasms of the ampulla of Vater (ampullary NEN) have features of both gastrointestinal and pancreato-biliary (PB) NEN. However, the limited number of studies examining ampullary NEN makes it difficult to clarify their unique characteristics. This study aimed to elucidate the clinical characteristics of ampullary NEN. Methods: We enrolled 162 patients with PB-NEN diagnosed at Kyushu University Hospital between 2011 and 2020. Clinical features, pathological diagnoses, treatments, and prognoses were retrospectively analyzed. We also compared ampullary NEN with pancreatic NEN (PanNEN). Results: We analyzed 10 ampullary NEN cases and 149 PanNEN cases. The ampullary NEN cases consisted of four cases of NET G1 (neuroendocrine tumor Grade 1), one NET G2 (Grade 2), and five NECs (neuroendocrine carcinoma). The incidences of NEC and cholangitis were significantly higher in ampullary NEN than in PanNEN. All ampullary NETs had a submucosal tumor-like appearance, as identified by endoscopic ultrasound-guided fine needle aspiration. We treated small NET G1 (<10 mm) with endoscopic papillectomy and large NET G1 with pancreaticoduodenectomy. There were no cases of recurrence after resection. All ampullary NECs presented with the characteristic endoscopic finding of a ‘‘crater sign” similar to deep-mining ulcers seen in gastric malignant lymphoma. Four cases underwent surgical resection, and one case was unresectable. Two patients who underwent multidisciplinary treatment were maintained without recurrence for over 2 years. Conclusions: Endoscopic findings showed identifiable distinctions between ampullary NETs and NECs.