Intraductal Papillary Mucinous Neoplasm Arising in a Heterotopic Pancreas: A Case Report

Abstract

To the Editor : A 44-year-old man was referred to our outpatient gastroenterology clinic for a 3-year history of abdominal bloating and epigastric pain, which were relieved by belching. Th e past medical history was notable for HIV diagnosed 11 years ago, with a preserved CD4 count and no history of opportunistic infections. His medication regimen included lamivudine, zidovudine, and nevirapine, which he had started in the last year. Th ere was no family history of gastroenterologic disease. Physical exam was unremarkable. Laboratory studies including liver function tests and serum amylase / lipase were normal. Because of his persistent unexplained symptoms, a computer tomography scan was obtained, which revealed a 3 × 4 cm complex cystic lesion in the greater curvature of stomach ( Figure 1 ). Subsequent endoscopic ultrasound revealed a subepithelial complex cystic mass at the junction of stomach body and antrum. Th e wall layer could not be clearly identifi ed. A fi ne-needle aspirate of the cyst revealed serous-appearing brown-tinged fl uid. Cytology revealed only very scant infl ammatory cells, and chemistries were notable for amylase 0 IU/L and carcinoembryonic antigen 319 ng / ml. Molecular analysis of the fl uid was also performed; the sample was negative for the K-ras mutation, but there were loss-of-heterozygosity (LOH) mutations of 10q and 17q. Th e LOH mutations were low amplitude in clonal extent, and interpreted as “ consistent with an indolent, low grade, benign neoplastic processes. ” Th e patient subsequently underwent a limited partial gastrectomy for excision of the mass. Pathology of the surgical specimen revealed a 3 cm heterotopic pancreas with a 0.9 cm intraductal papillary mucinous neoplasm ( Figure 2 ), with low-grade adenomatous cytologic features. Th e prevalence of heterotopic pancreas is not well established, but surgical and autopsy studies in the 1940 – 1950s suggest a prevalence ranging from 0.6 to 15 % ( 1,2 ). Th e most common locations of heterotopic pancreas are the stomach, duodenum, and jejunum, but other locations including the esophagus, common bile duct, mediastinum, and fallopian tubes have also been described ( 3 ). Heterotopic pancreas is most commonly found incidentally at endoscopy, surgery, or during other investigations. Although most patients are asymptomatic, heterotopic pancreas can occasionally lead to gastrointestinal obstruction, upper gastrointestinal bleeding, obstructive jaundice, and other presentations depending on the location of the abnormal tissue. In addition to eff ects on adjacent organs, heterotopic pancreatic tissue can itself undergo pathological changes including pancreatitis and rarely malignant transformation ( 4,5 ). To our knowledge, this is only the second reported case of intraductal papillary mucinous neoplasm in heterotopic pancreas, providing another example of the fact that heterotopic pancreas can develop pathological changes similar to the native pancreas ( 6 ).