Can You See the Carcinoid Tumor? A Case of Autoimmune Metaplastic Atrophic Gastritis (AMAG) and Carcinoid Tumor

Abstract

Atrophic gastritis is a known risk factor for the development of carcinoid tumor and gastric adenocarcinoma. In AMAG, there is destruction of parietal cells which leads to G-cell hyperplasia and elevated gastrin levels resulting in the proliferation of enterochrommaffin-like cells. These cells serve as precursors to carcinoid tumors, thus can be neoplastic in nature. A majority of carcinoid tumors appear on upper endoscopy (EGD) as polypoid lesions in the gastric body or fundus. We would like to present a unique case of carcinoid tumor in the context of AMAG, with grossly normal EGD. Our patient is a 25 year old female without significant past medical history with sole complaint of chronic dyspepsia and upper abdominal pain. She presented to clinic for a second opinion after a recent diagnosis of a neuroendocrine malignancy on EGD one month prior. The patient underwent repeat EGD with biopsies taken from the antrum, body, and fundus. An area of hypopigmented mucosa was identified in the antrum, prompting biopsies. The remainder of the stomach, duodenum, and esophagus were grossly normal. Pathology from the antrum and fundus all revealed chronic gastritis with mild enterochromaffin-like cell hyperplasia and severe reactive changes. The fundic biopsy showed chronic atrophic gastritis with antralized mucosa, suggestive of AMAG. The biopsies from the body of the stomach demonstrated well-differentiated neuroendocrine tumor (NET) grade 1, arising in the background of chronic atrophic gastritis. KI67 demonstrates proliferation index less than 2%. No lymphovascular invasion was seen. Her prior EGD showed well differentiated NET on antral biopsy. Patient underwent EGD/EUS with biopsies at a tertiary center, which was unremarkable, and biopsy showed atrophic gastritis. She was advised to repeat EGD every 6-12 months. This case raises concern for therapy modalities as minimal literature exists in regards to treatment of NET in the setting of AMAG with normal EGD. Given the lack of gross focality to the carcinoid lesion, does one resect or surveil? Although gastric carcinoid in the setting of atrophic gastritis is rarely malignant, one must ponder the malignancy potential given that we were unable to pinpoint the lesion despite multiple EGD's. Further cases must be studied to adequately manage such patients and better understand disease progression.3087_A Figure 1. EGD with normal appearing mucosa3087_B Figure 2. EGD with normal appearing mucosa and narrow band imaging