Diagnostic work-up of gastroenteropancreatic neuroendocrine tumors

Abstract

Neuroendocrine tumors are a heterogeneous group of malignancies that present a diagnostic challenge. The majority of patients (more than 60%) present with metastatic disease at diagnosis. The diagnosis is based on histopathology, imaging, and circulating biomarkers. The histopathology should contain specific neuroendocrine markers such as chromogranin A, synaptophysin, and neuron-specific enolase and also an estimate of the proliferation by Ki-67 (MIB-1). Standard imaging procedures consist of computed tomography or magnetic resonance imaging together with somatostatin receptor scintigraphy. 68Ga-DOTA-octreotate scans will in the future replace somatostatin receptor scintigraphy because they have higher specificity and sensitivity. Other positron imaging tomographic scanning tracers that will come into clinical use are 18F-DOPA and 11C-5HTP. Neuroendocrine tumors secrete many different peptides and amines that can be used as circulating biomarkers. The most useful general marker is chromogranin A, which is both a diagnostic and prognostic marker in most neuroendocrine tumors. However, there is still a need for improved biomarkers for early detection and follow-up of patients during treatment. In addition, molecular imaging can be further developed for both detection and evaluation of treatment.

Current Concepts in 68Ga-DOTATATE Imaging of Neuroendocrine Neoplasms: Interpretation, Biodistribution, Dosimetry, and Molecular Strategies

“…Somatostatin receptor (SSR) imaging offers an opportunity to identify receptor-expressing neuroendocrine neoplasms (NENs) (2,3). Radiolabeled somatostatin analogs (SSA) were introduced in the 1980s for imaging of NENs ( Fig.…”

Pancreatic Neuroendocrine Tumors: an Update

“…Magnetic resonance (MR) imaging techniques are particularly useful for lesions that are too small to be seen by CT or for the identification and follow-up of liver metastatic disease, where MR has been shown to be superior to CT [27][28][29]. The reported sensitivity of MR ranges from 85 to 100 % with a specificity of 75 to 100 % [25,27].…”

Review: Screening, Diagnosis and Management of Gastric Carcinoid

“…Plasma Chromogranin A (CgA): Chromogranin A, a neuroendocrine peptide precursor released by neuron secretory vesicles, has been widely accepted as a screening marker for neuroendocrine tumors [12][13][14]. Although use of plasma CgA as a diagnostic indicator has been supported by a high sensitivity, previous literature has criticized its use due to comparatively low specificity [15].…”

“…The majority of gastric NETs are discovered incidentally during surgery or diagnostic procedures [12]. Perhaps the greatest challenge in identifying patients who warrant screening for gastric carcinoid is its clinical silence.…”

“…An alternate for biochemical screening of carcinoids is 5-HIAA, a renally excreted serotonin metabolite produced by functioning carcinoid tumors [12]. There are several challenges in evaluation of 5-HIAA levels, the most obvious of which is the requirement of a 24 hour urine collection.…”