Early Definitive Diagnosis and Management of Incidental Neuroendocrine Tumors Found on Gastrointestinal Endoscopy

Neuroendocrine tumors (NETs) are tumors that originate from neuroendocrine cells and can be found throughout the body but are most commonly seen in the gastrointestinal tract, pancreas, and lungs. There is an increase in the diagnosis of NETs due to advances in diagnostic modalities. Although mucosal tumors are easily visualized on upper GI endoscopic imaging, neuroendocrine tumors are often missed due to their deep mucosal origin with normal overlying mucosa. We first present the case of a 46-year-old woman with anemia and epigastric discomfort who was found to have an incidental submucosal mass in the duodenal bulb on esophagogastroduodenoscopy (EGD), which on endoscopic ultrasound (EUS) with a fine needle biopsy (FNB) showed a neuroendocrine tumor. Imaging with CT, however, failed to detect the presence of the mass in the duodenum. Furthermore, a DOTATATE scan showed only a nonspecific signal near the liver. The patient then underwent an EGD-guided, laparoscopic, robot-assisted transduodenal resection of the tumor, together with the removal of enlarged peritumoral lymph nodes. Pathology showed a well-differentiated neuroendocrine tumor of the duodenal bulb with metastasis to one lymph node, which was confirmed via immunohistochemistry staining. The second case is of a 51-year-old female who presented with occasional constipation and rectal pain and was found to have a rectal polypoid lesion on her colonoscopy, jumbo biopsies of which revealed a NET. An EUS done for staging and endoscopic mucosal resection (EMR) revealed a grade 1 well-differentiated NET on pathology, which was confirmed by immunohistochemistry staining. These cases stress the need for timely, definitive diagnosis and intervention. Here, we discuss the clinical features and investigations of neuroendocrine tumors for early diagnosis and management.