Acinar cell carcinoma arising from gastric heterotopic pancreas: a rare case report

Heterotopic pancreas is an uncommon congenital anomaly that is typically asymptomatic and benign. Malignant transformation within heterotopic pancreatic tissue is exceedingly rare, and acinar cell carcinoma is an especially unusual subtype. Preoperative diagnosis is challenging due to marked variability in endoscopic manifestations and the frequent occurrence of negative biopsy results. We report the case of a 64-year-old male who presented with an 8-month history of abdominal mild pain and distension. Endoscopy revealed an approximately 4-cm mass at the greater curvature of the gastric body, with surface congestion and erosion. Initial biopsies were non-diagnostic. Endoscopic ultrasound(EUS) and computed tomography (CT) indicated a spherical-like mass protruding into the gastric lumen, exhibiting homogeneous hypoechoic features. The patient underwent diagnostic endoscopic submucosal dissection (ESD). Imaging findings in conjunction with postoperative pathology indicated that the gastric lesion was an acinar cell carcinoma (ACC) originating from ectopic pancreatic tissue. Subsequently, to achieve curative resection, the patient underwent additional proximal gastrectomy with D1 + lymphadenectomy and esophagogastrostomy. Fortunately, no residual tumor or lymph-node metastasis was identified in the post-operative surgical specimen. During the 1-year follow-up period, the patient remained disease-free, with stable tumor marker levels and no evidence of recurrence on serial endoscopic and abdominal imaging evaluations. Ectopic pancreatic malignancy is rare, and ectopic pancreatic malignancy to acinar cell carcinoma is even rarer, the accurate identification of such lesions is crucial,, as complete imaging evaluation and thorough pathological analysis are essential for definitive diagnosis. Long-term postoperative monitoring plays a key role in accumulating clinical experience in the follow-up management of these patients.