Case Report: Unicentric Castleman disease at the superior border of the pancreatic body mimicking a pancreatic neuroendocrine tumor: a case report and literature review.

Peripancreatic unicentric Castleman disease is rare and may mimic a primary pancreatic neoplasm because it often presents as a well-circumscribed hypervascular mass. We report a 26-year-old woman with type 2 diabetes mellitus in whom an incidentally detected upper abdominal mass was initially considered to arise from the pancreatic body. Computed tomography and magnetic resonance imaging showed a sharply marginated hypervascular lesion with diffusion restriction at the superior border of the pancreatic body, leading to a preoperative suspicion of pancreatic neuroendocrine tumor. Laparoscopic exploration revealed a well-encapsulated mass in the lesser sac closely abutting the superior surface of the pancreas. A clear dissection plane between the lesion and the pancreatic parenchyma allowed complete excision without pancreatic resection or splenectomy. Histopathological examination confirmed hyaline vascular-type unicentric Castleman disease. The postoperative course was uneventful, and no residual or recurrent lesion was detected during 1 year of follow-up; glycemic status also remained stable. This case highlights that close proximity of a hypervascular mass to the pancreas does not necessarily indicate pancreatic origin. Careful multiplanar imaging and direct intraoperative assessment of the lesion-pancreas interface may help determine the appropriate surgical extent and avoid unnecessary pancreatic resection when complete excision is technically feasible.