A case of pancreatic acinar cell carcinoma implantation in multiple branches of the pancreatic duct without main tumor continuity: a rare case report.

Background: Pancreatic acinar cell carcinoma (PACC) is a rare subtype of pancreatic cancer and the clinicopathological behavior of PACC is not yet fully understood. PACC rarely invades the main pancreatic duct (MPD), which causes intraductal growth. Thus, herein, we have reported a rare case of PACC that invaded the MPD and disseminated to the branches of the pancreatic duct (BDs) without exhibiting any continuity with the main tumor. Case Description: A 60-year-old man was found to have a hypo echoic pancreatic head mass on abdominal ultrasonography during a routine medical checkup. In computed tomography, a 30-mm hypo-dense mass was found in the pancreas head. An endoscopic retrograde pancreatography was performed to collect pancreatic juice for cytological examination. MPD was narrowing in pancreatic head and caudal MPD was slightly dilated. Although no malignant cells were detected, a pancreaticoduodenectomy was performed. Histological examination of the excised specimen confirmed the diagnosis of PACC with MPD invasion. Furthermore, tumor implantation was detected in multiple BDs that were downstream of the main tumor, without any continuity with the main tumor. Conclusions: PACC can metastasize and get implanted in multiple BDs. Thus, post-surgical relapse can occur due to metastatic lesions implanted in the remnant pancreas.