Gastric Neuroendocrine Tumor: A Rare Tumor With Different Types

Abstract

Gastric neuroendocrine tumors (GNETs) are rare submucosal lesions that arise from enterochromaffin-like cells of the stomach. GNETs consist of a large group of neoplasms comprising tumor types of varying pathogenesis, biological behavior and histomorphologic characteristics. 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, less than 2% of all NETs and less than 1% of all stomach neoplasms. Considering the rarity of this neoplasm, we are reporting a case with this disease focusing on the importance of a timely diagnosis in improving outcomes. 63-year-old female presented with progressive dysphagia and postprandial emesis of few weeks duration. CT and EGD showed pre-pyloric submucosal non-obstructing mass measuring 3x3 cm. Endoscopic Ultrasound (EUS) showed a well-defined round mass arising from the muscularis propria measuring 4x4 cm. Fine needle biopsy (FNB) showed well-differentiated neuroendocrine tumor. This diagnosis was supported by strong and diffuse immunoreactivity for Cam 5.2 and synaptophysin. Chromogranin showed patchy positivity. Ki-67 stain showed positivity in less than 2%. She underwent subtotal gastrectomy and lymph node dissection with follow up Octreotide scan showing no abnormal focal radiotracer uptake to suggest residual or metastatic tumor. GNETs are classified into four clinicopathological types. Type I is the most common, related to atrophic gastritis, represents as multiple neoplasms and has an excellent prognosis after resection. Type II is related to hypergastrinemia secondary to gastrin-secreting tumor. Both type I and II are usually benign with low malignancy risk. Type III is a sporadic tumor, solitary and infiltrating, well-differentiated and usually accompanied by angioinvasion and lymph node metastasis resulting in a poorer prognosis. Type IV is rare, usually solitary, poorly differentiated with an aggressive behavior and extremely poor prognosis. Our patient had type III GNET with good response to surgical treatment and no residual tumor on follow up implicating the importance of a timely diagnosis of such tumors to improve outcomes. In conclusion, type III GNETs is a sporadic tumor usually accompanied by local invasion and lymph node metastasis resulting in a poor prognosis. Awareness of such tumor and a timely diagnosis using EUS can result in improved outcomes after surgical treatment.Figure: CT scan images show pre-pyloric non-obstructing mass measuring 3x3 cm.Figure: EGD (upper left) shows pre-pyloric submucosal non-obstructing mass measuring 3x3 cm. EUS (upper right) shows a well-defined round mass arising from the muscularis propria measuring 4x4 cm. EUS-guided fine needle core biopsy (lower left) shows a monotonous population of uniform appearing cells with immunostaining (lower right) showing synaptophysin positivity which is expected in neuroendocrine tumors.