A Rare Case of Gastric Neuroendocrine Tumor in a Patient with History of Familial Adenomatous Polyposis - Is There an Association?

Abstract

Familial adenomatous polyposis (FAP), is one of the genetic colorectal cancer syndromes. It is an autosomal dominant inherited disease caused by a somatic mutation in the APC tumor suppressor gene on the chromosome 5q21 with an estimated prevalence of this syndrome between 1 per 5,000-7,000. Adenomatous polyps of the upper intestinal tract (gastric, duodenal, periampullary, and ileal adenomas) are also commonly found in familial adenomatous polyposis (FAP). Gastric neuroendocrine tumors (GNETs) are a rare disease with a reported incidence of 1 to 2 cases/1,000,000 persons per year, comprising 8.7% of gastrointestinal neuroendocrine tumors. Rarely have GNETs been associated with FAP. We present a rare case of gastric neuroendocrine tumor in a patient with FAP. A 56-year-old woman with a past medical history of hypertension, hyperlipidemia, type 2 diabetes, hypothyroidism and FAP with a history of colectomy performed in 1989. As part of her surveillance for extracolonic manifestations of FAP, an Upper endoscopy was performed. Upper endoscopy revealed few 2-3mm gastric body and antral polyps, and multiple 2-3 mm polyps in the duodenal bulb.(Figure 1) Duodenal biopsy showed tubular adenomas. Biopsy of the gastric polyps revealed tubular adenomas with low-grade dysplasia and a low-grade neuroendocrine neoplasm. The tumor cells were positive for pancytokeratin (AE1/AE3), synaptophysin and chromogranin staining and were negative for CD3, CD20, and CD138, consistent with a diagnosis of neuroendocrine tumor. (Figure 2).The patient is undergoing further workup including a magnetic resonance imaging of abdomen and pelvis, and an octreotide scan to stage her disease.2663_A Figure 1. Endoscopic view of gastric and duodenal polyps2663_B Figure 2. Synaptophysin Positive, 400x, confirming presence of carcinoid tumor cells.Gastrointestinal neuroendocrine tumors may be found in association with neurofibromatosis (periampullary carcinoids), Zollinger-Ellison, and multiple endocrine neoplasia syndromes and have rarely been reported in association with FAP. Patients with FAP have dysregulation of the Wnt/b-catenin signaling pathway. Recent findings of b-catenin mutations in neuroendocrine tumors suggest that Wnt/b-catenin alterations may be the common pathway for both tumors. The presence of these two rare entities in the same patient might suggest an association and further research is indicated to determine this association.