Pancreatic-Type Acinar Cell Carcinoma of the Duodenum: A Case Report and Literature Review

Acinar cell carcinoma (ACC) is a rare malignant tumor arising from pancreatic exocrine cells. While it typically originates in the pancreas, ectopic occurrences, especially in the duodenum, are extremely uncommon. Few reports exist of duodenal ACC, particularly those presenting as large tumors.

An 83-year-old man presented with melena. Endoscopy and imaging revealed a large mass, approximately 7 cm in size, extending from the duodenal bulb to the descending portion of the duodenum. Contrast-enhanced CT showed no evidence of extramural invasion or distant metastasis. Although biopsy confirmed malignancy, a definitive diagnosis could not be established preoperatively. The patient underwent pancreaticoduodenectomy. Postoperative histopathological examination, including immunohistochemical staining positive for trypsin, confirmed the diagnosis of pancreatic-type ACC, likely arising from ectopic pancreatic tissue in the duodenum.

We report a rare case of a giant pancreatic-type ACC of the duodenum, which was strongly suspected to have arisen from ectopic pancreatic tissue. This case highlights the diagnostic challenges associated with pancreatic-type ACC of the duodenum and adds valuable information to the limited literature on this rare entity.