Ectopic Pancreatic Adenocarcinoma Arising in the Mesentery of the Jejunum: A Case Report.

INTRODUCTION

Ectopic pancreas is defined as pancreatic tissue lacking anatomical and vascular continuity with the main pancreas. Malignant transformation within ectopic pancreatic tissue is extremely rare, and cases arising in the mesentery are exceptionally uncommon. We report a rare case of adenocarcinoma arising from ectopic pancreatic tissue in the proximal jejunal mesentery.

CASE PRESENTATION: An 80-year-old man presented with abdominal pain. Contrast-enhanced CT showed a 3-cm mass adjacent to the proximal jejunum, initially suspected to be a jejunal submucosal tumor, such as gastrointestinal stromal tumor. Laparoscopy identified a firm mesenteric tumor closely associated with the superior mesenteric artery and jejunal branches, necessitating conversion to open surgery. The tumor was completely excised while preserving the small intestine. Histopathological examination demonstrated well-differentiated adenocarcinoma arising within ectopic pancreatic tissue containing acinar, ductal, and islet of Langerhans. Immunohistochemistry showed positive staining for carbohydrate antigen 19-9, p16, p53, and S100A4, supporting the diagnosis of pancreatic ductal adenocarcinoma. The postoperative course was uneventful except for transient paralytic ileus. The patient was discharged on POD 19 and has remained recurrence-free for 9 months.

CONCLUSIONS

Adenocarcinoma arising from ectopic pancreatic tissue in the mesentery is exceedingly rare and difficult to diagnose preoperatively. Complete surgical excision is essential for definitive diagnosis and curative treatment. Further case accumulation is required to better define its clinical characteristics and optimal treatment strategies.