A case of pancreatic hamartoma with difficult preoperative diagnosis.

A 70-year-old woman presented with a mass in the tail of the pancreas, which was incidentally detected during screening with plain computed tomography (CT). Dynamic CT revealed a 14-mm mass in the pancreatic tail, characterized by low density in the early arterial phase and delayed contrast enhancement from the portal to the equilibrium phase. Magnetic resonance imaging revealed that the tumor had slightly high signal intensity dorsally and slightly low signal intensity ventrally on T1-weighted fat suppressed images, and low signal intensity on T2-weighted images. Endoscopic ultrasonography revealed a well-demarcated hypoechoic mass. However, biopsy showed no definitive tumor cells. Due to the difficulty in ruling out acinar cell carcinoma, laparoscopic distal pancreatectomy was performed. Histologically, the lesion revealed an enlarged pancreatic duct and adenohypophysis with fibrosis, lacking concentric elastic fibers in the duct walls, peripheral nerves, and islets of Langerhans. The final pathological diagnosis was pancreatic hamartoma-a rare tumor with only 52 cases reported previously in the literature. Preoperative histological diagnosis is extremely challenging. Here, we report a case of pancreatic hamartoma that was difficult to distinguish from malignant tumor preoperatively.