Intestinal Neuroendocrine Tumors: The Hidden Hazards

Abstract

Neuroendocrine tumors (NETs) arise from secretory cells found throughout the body, which makes them biologically & clinically diverse; a diagnostic challenge for both researchers & practitioners. It is not uncommon for them to be diagnosed serendipitously. Two such cases exemplify the abstruse presentations of such tumors. Case 1: A 67 year old male came with abdominal pain & constipation for 5 days. An abdominal CT scan revealed a 1x2 cm necrotic mass adjacent to the uncinate process of pancreas & contiguous with multiple loops of bowel. An endoscopic biopsy with FNA & flow cytometry was non-diagnostic. Patient's symptoms improved with laxative use until 4 months later, when constipation returned. Repeat abdominal CT scan revealed that the mass had increased in size to 7x4 cm, with two new paraaortic lymph nodes. An exploratory laparoscopy was performed where only a partial resection was possible. Histology showed a low grade NET of gastrointestinal tract origin. Patient is currently undergoing octreotide therapy. Case 2: A 60 year old male with hypertension presented after having 3 episodes of bright red blood per rectum for 1 day. He continued to have multiple bleeding episodes in the ED, requiring resuscitation with 11 units of packed RBCs. An upper endoscopy showed a 3 cm clean based duodenal bulb ulcer with no signs of active bleeding. A bleeding scan revealed bleeding at the hepatic flexure & an emergent right hemi-colectomy was performed. During the procedure, liver was notable for multiple small lesions. A biopsy confirmed a low grade NET. Remarkably, the colonic specimen was completely normal. An octreotide scan done later showed increased radiotracer uptake in the mid transverse-colon, presumably the site of bleeding.Figure 1Figure 2Figure 3Discussion: Annual incidence of gastroenteropancreatic NETs in the US is 3.65/100,000 people, making it extremely rare. Patients with NETs may or may not have symptoms attributable to hormonal secretion posing a formidable diagnostic challenge. Revisiting our first patient's prior CT scans, it was found that the size of the tumor had been stable at 8 cm. Carcinoid tumors are highly vascular & can appear iso-dense with liver & pancreas on conventional CT scans, leading to diagnostic errors. Serum chromogranin A along with radiolabeled somatostatin receptor scintigraphy can be extremely useful to visualize non-functioning tumors. Patients with non-metastatic tumors should be treated with resection of the involved segment & small bowel mesentery. Somatostatin analogues & the molecularly targeted agents everolimus & sunitinib improve progression-free survival duration relative to supportive care alone in patients with metastases from a non-functioning pancreatic NET.