Gastric Heterotopic Pancreas with Apparent Malignant Transformation after 24 Years' Clinical Surveillance

Abstract

The case of a patient in whom malignant transformation of a gastric heterotopic pancreas was suspected after clinical surveillance for 24 years is presented. A 66-year-old man was found to have a submucosal tumor in the gastric antrum in 1997, and since there was no sign of change in its size or shape, a policy of watchful waiting was adopted. On upper gastrointestinal endoscopy conducted during a regular health checkup in March 2021, the tumor was observed to have increased in size. Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) was therefore performed, and adenocarcinoma was diagnosed. Abdominal contrast-enhanced computed tomography (CT) showed a submucosal mass measuring 25 mm × 19 mm in the gastric antrum, and positron-emission tomography CT (PET-CT) showed abnormal uptake only at that site. Blood tests showed that CA19-9 was elevated at 64 U/mL, but CEA, DUPAN-2, and SPAN-1 were normal. In addition to the endoscopic ultrasound findings, the fact that there were no other signs indicative of any other malignancy on PET-CT strongly suggested malignant transformation of the gastric heterotopic pancreas. Open distal gastrectomy and D2 lymph node dissection were performed. Postoperative histopathological examination demonstrated that this was a heterotopic pancreas-derived adenocarcinoma (General Rules for the Study of Pancreatic Cancer, 7th Edition : pT2N0M0, Stage Ib). The patient's postoperative course was uneventful, and the patient was discharged on postoperative Day 11, with S-1 as adjuvant chemotherapy. Six months postoperatively, the patient continues to survive recurrence-free.