Pancreatic Acinar Metaplasia (PAM) in the Distal Esophagus - Is it a Variant of Pancreatic Heterotopia or an Under Reported Histological Finding?

Abstract

Purpose: Introduction: PAM consists of nests or lobules of pancreatic acinar cells which are characterized by the presence of fine acidophilic granules in the apical cytoplasm and prominent basophilia of the basal portion of the cells. They contain exocrine pancreatic markers such as lipase, trypsinogen, and pancreatic alpha-amylase. Pancreatic heterotopia (PH) (pancreatic rest) is distinguished from PAM by the presence of ductal elements, pancreatic stroma or well defined islets. We report a case of PAM above the gastro esophageal junction (GEJ) and present a brief review of the literature. Case: A 77 year old woman with known GERD for more than 10 years underwent a follow up EGD for refractory symptoms. Patient had a known history of acoustic neuroma treated with resection and radiotherapy, and hyper plastic colon polyps. The current EGD showed a small hiatus hernia and irregular Z line, a fundic gland polyp, and erythematous gastropathy. Biopsies of the distal esophagus showed gastric mucosa with ectopic pancreatic tissue and adjacent inflammation. There was no evidence of BE or H. Pylori gastritis. Discussion: Out of 644 patients who underwent EGD Johansson et al identified PAM above GEJ in 40 (6%), below GEJ in 67 (10%) and both above and below GEJ in 14 (2%). Female gender, H. Pylori infection and GERD were associated with PAM above the GEJ. Focal PAM was found in 11 of 350 (3.14%) biopsies of Barrett's mucosa from 120 patients with BE enrolled in a clinical efficacy trial of omeprazole versus ranitidine for treatment of GERD. Another study by Popiolek et al examined GEJ specimens from 69 young adults and children and found that PAM was present in 16% of the study population and was not associated with BE. The data suggested that PAM at the GEJ develops independently of inflammation and was felt to be a congenital. In contrast, anecdotal reports of heterotopic pancreas (commonly recognized as pancreatic rest) causing abdominal pain, acute pancreatititis, GI bleeding, gastric perforation, gastric outlet obstruction, obstructive jaundice, intussuception, pseudocyst formation, and rarely adenocarcinoma have been described. The presence of PAM above GEJ is likely congenital and may have no clinical relevance or malignant potential. However it remains a distinct and common histological finding and may be underreported in clinical practice.