Supplementary Material for: Advanced Adenosquamous Carcinoma of the Ampulla of Vater Treated with Adjuvant Chemotherapy After Pancreaticoduodenectomy

Introduction: Adenosquamous carcinoma (ASC) of the ampulla of Vater (AmV) is rare. The prognosis is generally worse in patients undergoing resection of ASC of the AmV than in those undergoing resection of adenocarcinoma of the AmV because the former shows early recurrence after surgery. A treatment strategy for adenosquamous carcinoma of the AmV has not been established, and the efficacy of adjuvant chemotherapy after curative resection is unclear. Given the paucity of data, we report a case of ASC of the AmV that was curatively resected and treated with adjuvant chemotherapy. Case presentation: A 66-year-old man presented with pruritus and anorexia. Contrast-enhanced computed tomography revealed a tumor measusing 1.6 cm in diameter located at the AmV and distal bile duct . Biopsy revealed adenocarcinoma of the AmV. The patient underwent subtotal stomach-preserving pancreaticoduodenectomy. Histopathological examination contradictorily revealed adenosquamous carcinoma of the AmV and lymph node metastases. The postoperative course of the patient was uneventful, and he was discharged on day 25. The patient underwent S-1 adjuvant chemotherapy for 6 months and did not exhibit any postoperative recurrence for a follow-up duration of 28 months. Conclusion: Although treatment strategy for ASC of the AmV has not been established, our case shows that surgery followed by S-1 adjuvant chemotherapy could improve prognosis of patients with such tumors. However, further research is required to determine the efficacy of adjuvant chemotherapy and treatment strategies for resectable ASC of the AmV.