A case of pathologically complete response after preoperative chemotherapy in a pancreatic acinar cell carcinoma patient with portal vein tumor thrombosis.

Preoperative treatment is being proposed as a standard treatment for pancreatic ductal adenocarcinoma though few cases show a pathologically complete response. On the other hand, there is no consensus regarding preoperative chemotherapy for pancreatic acinar cell carcinoma (ACC). The present study described a rare case of ACC in the pancreatic head with portal vein tumor thrombosis (PVTT) treated with preoperative chemotherapy using modified FOLFIRINOX, which achieved a pathologically complete response. A 65-year-old man was referred for consideration of treatment strategy. Contrast-enhanced abdominal computed tomography revealed a pancreatic tumor and PVTT. The pancreatic tumor was diagnosed as ACC by an endoscopic ultrasound-guided fine-needle aspiration biopsy. Initially, the tumor was assessed as unresectable due to the presence of PVTT, and therefore, a chemotherapy using modified FOLFIRINOX was administered. After 14 courses of the chemotherapy, imaging studies revealed that the tumor and PVTT showed marked reduction in size; thus, the patient underwent pancreaticoduodenectomy with combined resection of the portal vein (PV). A pathological examination uncovered a complete degeneration of the primary tumor and the PV embolus without any residue of carcinoma. The patient did not receive adjuvant chemotherapy and survived with no evidence of recurrence for 33 months after surgery. The chemotherapy using modified FOLFIRINOX could give a complete response in patients with pancreatic ACC with PVTT.