Pancreatic hamartoma: Possibility of a preoperative diagnosis via endoscopic ultrasound-guided fine-needle aspiration biopsy.

Endoscopic ultrasound-guided fine-needle aspiration biopsy (EUS-FNAB) is useful for preoperatively diagnosing various pancreatic tumors. Although there is a risk of complications, such as pancreatitis, this procedure achieves the crucial need of reducing unnecessary invasive surgery for benign lesions. Herein, we reported a surgically resected case of pancreatic hamartoma in the pancreatic head whose retrospective analysis revealed that the specimens obtained via EUS-FNAB contained hamartoma fragments. Pancreatic hamartoma is an extremely rare benign disease that is exceptionally difficult to diagnose before surgical resection owing to its rarity and lack of established imaging findings. To the best of our knowledge, the preoperative diagnosis of pancreatic hamartoma via EUS-FNAB specimens has not been reported to date. Herein, postoperative EUS-FNAB evaluation revealed a collection of pancreatic hamartoma lesions, although the initial diagnosis was pancreatic tissue with focal atrophy and fibrosis. Diagnosis using EUS-FNAB can be challenging owing to the very small sample size. If mature acini and ducts with fibrous stroma without islets are observed in the EUS-FNAB specimen, pancreatic hamartoma should be considered as a differential diagnosis. Thus, careful follow-up or reexamination of EUS-FNAB should be considered instead of surgery if a benign lesion is suspected preoperatively.