A resected case of recurrent ITPN in the remnant pancreas after pancreatoduodenectomy

BACKGROUND: Since intraductal tubulopapillary neoplasm (ITPN) is a rare disease, the clinical features of ITPN, especially the characteristics related to recurrence, have not been revealed. We performed a total remnant pancreatectomy for a patient whose ITPN recurred 16 months after pancreatoduodenectomy (PD). We report useful findings to clarify how ITPN reoccurs based on this experience and previously reported cases. CASE PRESENTATION: A 61-year-old male patient was diagnosed with pancreatic cancer and underwent PD. However, a postoperative pathologic examination diagnosed ITPN with invasive cancer. After receiving adjuvant chemotherapy, he was hospitalized for pancreatitis 16 months after the operation. He was diagnosed as having recurrence near the pancreato-jejunal anastomosis based on detailed examinations and underwent a remnant total pancreatectomy. From the results of the histopathological examination, he was found to have a recurrence of ITPN as a polypoid mass without invasion distant from the surgical stump of the first operation. Furthermore, tumor cells floating in the main pancreatic duct distant from the main tumor were observed at three locations. REVIEW OF THE LITERATURE: Including our case, five cases of recurrence in the remnant pancreas after surgery for ITPN have been reported. Recurrence in the main pancreatic duct was observed in four of these five cases. The primary tumor, which recurred in the remnant pancreas after surgery, was characterized as being relatively small and less invasive; however, Ki-67 labeling index was high. In immunohistochemical examination, the expression of MUC6, which is not one of characteristics of ITPN, tended to be positive. CONCLUSION: In this case, tumor cells were floating inside the pancreatic duct at several locations. From the results of this case and a review of previous reports, the cause of ITPN recurrence in this case seemed to be due to tumor cells leaving the tumor and implanting into the pancreatic duct.