[A Case of Invasive Intraductal Papillary Mucinous Neoplasm(IPMN)Where Determining the Intraoperative Resection Margin Was Challenging].

An 75-year-old man was diagnosed with a 4-mm branch-duct type intraductal papillary mucinous neoplasm(IPMN)in the pancreatic tail and placed under observation. After 3 years and 6 months, endoscopic ultrasound(EUS)revealed a suspected pancreatic mass, prompting referral. Contrast-enhanced CT showed a 7-mm dilation of the main pancreatic duct without clear enhancing nodules. ERCP detected a 2-cm region with poor visualization of the branch ducts and ductal narrowing. MRCP revealed a faint high-intensity signal on diffusion-weighted imaging. EUS identified a 7-mm hypoechoic mass with irregular margins, and fine-needle aspiration(FNA)suggested atypical glands. The patient underwent a distal pancreatectomy with lymph node dissection. Histopathological examination revealed an IPMN extending 81 mm, with an invasive IPMN(IPMC)measuring 5 mm located 2 cm from the surgical margin. Three years and 4 months postoperatively, the patient remained recurrence-free. Recurrence is common when an IPMN progresses to invasive IPMC. This case underscores the challenges of preoperative diagnosis and is reported along with a brief literature review.