A 71-year-old man was treated with tumor-forming pancreatitis in the pancreatic head. The tumor presented with rapid growth and duodenal invasion. Pancreaticoduodenectomy was performed with the diagnosis of carcinoma based on duodenal invasion with hemorrhage. Histopathological findings showed acinar structures with rosette-arranged circular cells. Immunohistochemical examination was positive for BCL-10 and INSM-1 and acinar cell carcinoma with neuroendocrine differentiation. CEA elevation and multiple liver metastases were found six months after resection. Needle biopsy of the liver metastases showed a recurrent acinar cell carcinoma component which was immunohistochemically positive for BCL-10 and INSM-1. A BRCA2 genetic mutation was shown by multi-gene cancer panel testing from the primary pancreatic tumor. Modified FOLFILINOX therapy followed by maintenance olaparib therapy was administered. The patient is alive with continuous shrinkage of metastatic lesions 20 months after resection.