A Case of Intraductal Tubulopapillary Neoplasm of the Pancreas Requiring Superior Mesenteric Vein-Portal Vein Axis Resection after Systemic Chemotherapy.

INTRODUCTION: Intraductal tubulopapillary neoplasm (ITPN) is a rare intraductal pancreatic tumor, accounting for approximately 3% of all intraductal neoplasms. ITPN is characteristically paucimucinous and lacks low-grade (adenomatous) components. Since reported cases of ITPN remain limited, its prognosis, prognostic factors, and role of perioperative chemotherapy are not well defined. CASE PRESENTATION: A 64-year-old man presented with loss of appetite and abdominal pain in year X-1. Endoscopic US-guided fine-needle aspiration (EUS-FNA) was performed, and the findings showed atypical epithelial cells suspicious for adenocarcinoma. The lesion was radiologically assessed as borderline-resectable pancreatic head cancer with portal venous involvement. Curative-intent resection was attempted at the referring hospital; however, the tumor was judged intraoperatively to be locally unresectable because safe vascular dissection around the superior mesenteric vein (SMV) was difficult. Choledochojejunostomy, cholecystectomy, and gastrojejunostomy were performed for obstructive jaundice and duodenal stenosis. From October X-1, the patient received gemcitabine plus nab-paclitaxel, followed by tegafur/gimeracil/oteracil. The maximum tumor diameter decreased from 60 to 50 mm, and the imaging response to systemic chemotherapy was classified as stable disease according to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, without distant progression. In May X, the patient was referred to our department for consideration of surgical treatment. Repeat EUS-FNA strongly suggested ITPN. Subtotal stomach-preserving pancreatoduodenectomy with SMV-portal vein (PV) axis resection and reconstruction was performed using a right common femoral vein graft. Postoperative right deep femoral vein thrombosis was managed with anticoagulation. The patient was discharged on POD 16, and follow-up CT 1 year after surgery confirmed thrombus resolution. Histopathological examination confirmed invasive ITPN without lymph node metastasis or vascular invasion. The histological treatment effect was classified as grade 1a according to the Japanese classification of pancreatic carcinoma by the Japan Pancreas Society, eighth edition, and as grade I according to the Evans classification. Adjuvant chemotherapy was not administered. The patient remained disease-free 29 months after surgery. CONCLUSIONS: This case highlights the importance of multidisciplinary re-evaluation in pancreatic tumors initially managed as pancreatic ductal adenocarcinoma, particularly when an unusual histology such as ITPN is suspected.