Unusual Tissue – Unusual Issue: Pancreatic Heterotopia Presenting as Gastric Outlet Obstruction

Pancreatic heterotopia (PH) is a common, but typically small (<1 cm), incidental and asymptomatic finding; however, PH should be considered even for large and symptomatic upper gastrointestinal masses. A 27-year-old white woman presented with a 3-week history of burning epigastric pain, nausea, early satiety, and constipation. Physical examination revealed epigastric and right upper quadrant tenderness with normal laboratory workup, but imaging revealed a 5-cm, partly cystic mass arising from the gastric antrum with resulting pyloric stenosis and partial gastric outlet obstruction. Endoscopic ultrasound-guided fine needle aspiration revealed PH – an anomalous pancreatic tissue lying in a nonphysiological site. The patient ultimately underwent a resection and recovered uneventfully, with a complete pathologic examination revealing normal exocrine pancreatic tissue (PH type 2) without malignant transformation. We report a case of heterotopic pancreas manifesting as severe gastric outlet obstruction, in addition to a thorough diagnostic workup and surgical follow-up, in a young adult. Differential diagnoses and features that speak to benignity of a large, symptomatic mass lesion (PH in particular) are discussed.

Mixed Acinar-Neuroendocrine Carcinoma of the Stomach: A Case Report and Review of the Literature

Introduction/Objective Mixed Acinar Neuroendocrine Carcinoma (MACNEC) is rare and usually occurrs in the head of the pancreas. This is an epithelial neoplasm of the pancreas exhibiting both acinar and neuroendocrine differentiation. Each component must represent at least 30% of the tumor. Extrapancreatic acinar cell carcinoma arising in the stomach are also rare and represent &lt;1% of all gastric neoplasms. Here we report a case of MACNEC arising in the stomach of a 60 yo female and we review the literature. Methods The specimen was formalin-fixed and paraffin embedded. 4-microns sections of the tumor block were stained for hematoxylin and eosin and immunostained for CAM5.2, Chromogranin, synaptophysin, trypsin, chymotrypsin, BCL10, HepPar1 and AFP using a Ventana Discovery XT automated system (Ventana Medical Systems, Tucson, Ariz) as per manufacturer’s protocol with proprietary reagents. Results The patient presented with heartburn and weight loss. An upper endoscopy revealed an ulcer along the stomach greater curvature. Endoscopic ultrasound revelaed an hypoechoic round mass involving the submucosa. Imaging showed no lesions in the pancreas. A stomach wedge resection was performed: a 1.2 x 0.6 x 0.5 cm. submucosal tan-brown mass was found. Microscopically the tumor had alternated solid/acinar areas with cords/ribbons neuroendocrine-like areas. Both components were immunohistochemically positive for keratin (CAM 5.2), chromogranin (diffuse), and synaptophysin (patchy). The trypsin, chymotrypsin and BCL10 immunostains were patchy and stained 30 to 40% of the tumor. The immunostains for HepPar-1 and AFP were negative. These results support the diagnosis of MACNEC. Pancreatic heterotopia was not identified in the tissue examined. The margins of resection were free of tumor. The tumor was staged as T1NXMX. The patient has been under close surveillance for 3 years and she has no radiographic evidence of tumor recurrence or metastases. Conclusion We found only 6 prior cases of MACNEC originating in the stomach. They had similar histopathologic and immunohistochemical features. In the absence of a pancreatic lesions, in this patient the tumor may have originated from ectopic pancreatic tissue or from a pluripotent stem cell in the stomach.

Pancreatic Endocrine Heterotopia Involving Meckel’s Diverticulum: A Potential Mimic of Neuroendocrine Tumor

Pancreatic heterotopia most commonly occurs in the upper gastrointestinal tract, but can occur in other sites, including Meckel’s diverticulum. When multiple histologic elements of the pancreatic tissue (acini, ducts, and endocrine cells) are present, the diagnosis is typically straightforward. In this article, we report a rare case of pure endocrine pancreatic heterotopia involving a Meckel’s diverticulum, a potential mimic of a well-differentiated neuroendocrine tumor. Several features were useful in making the distinction, including lack of desmoplasia and mass forming lesion, and immunohistochemical staining in a physiological pattern similar to that of islets of Langerhans. It is important for pathologists to be aware of this entity and its features to avoid misdiagnosis of a neuroendocrine tumor.

A Rare Case of Well-Differentiated Neuroendocrine Tumor Arising From a Jejunal Pancreatic Heterotopia

Pancreatic heterotopia is a well-described entity occurring at multiple abdominal sites, most commonly the stomach and small intestine. They can develop similar disease processes as the pancreas ranging from acute pancreatitis, cyst formation, or neoplasms, most commonly ductal adenocarcinoma. Neuroendocrine tumors (NETs) arising in pancreatic heterotopias are exceedingly rare with only 3 prior published cases. In this article, we describe the first reported case of a NET arising in a jejunal pancreatic heterotopia in a 59-year-old woman presenting with abdominal pain and diarrhea. The submucosal tumor was composed of a well-differentiated NET (World Health Organization grade 1) directly intermixed with a heterotopic pancreas consisting of acinar cells, islet cells, and ducts. This case illustrates that NETs can occur in association with pancreatic heterotopias at any site. Also, the importance for pathologists to recognize that pancreatic heterotopias can give rise to a variety of neoplasms and is not limited to ductal adenocarcinoma.