Gastrointestinal Carcinoids: The Evolution of Diagnostic Strategies

Abstract

Carcinoid tumors are rare, often insidious neoplasms arising from neuroendocrine cells. The majority arise in the gastrointestinal system, and are often incidentally found during investigation, although some may present as an emergency bleed or perforation. The prosaic symptoms of flushing, diarrhea, and sweating are often overlooked; thus, the diagnosis is usually much delayed and the tumor is advanced at presentation. This diagnostic delay renders effective management difficult and adversely affects outcome. This overview provides a current assessment of the evolution of the diagnostic techniques available to establish an accurate biochemical (5-hydroxyindole-3-acetic acid and chromogranin A) and topographic diagnosis (octreoscan, radio-labeled metaidobenzylguanidine, computerized tomography, magnetic resonance imaging, positron emission tomography, enteroclysis, endoscopic ultrasound, enteroscopy, capsule endoscopy, and angiography) of carcinoid tumors. The utility and shortcomings of the respective modalities available are evaluated. Although considerable advances have been made in establishing the diagnosis of carcinoid tumors and in defining the topography of metastatic disease, the major limitation is the inability to establish an early and timely diagnosis before the advent of metastatic disease.

The Hidden Evil: Gastrointestinal Bleed and Small Bowel Obstruction Caused by Carcinoid Tumor Found on Exploratory Laparotomy

“…Second, carcinoid tumors are mostly asymptomatic but can sometimes cause small bowel obstruction and rarely, bleeding too. Third, CT and MRI may be used for initial localization of the tumor only because both imaging techniques may miss lesions otherwise detected by 111In-octreotide scintigraphy; one study has shown that lesions in 50% of patients were missed, especially in lymph nodes and extrahepatic locations [6,7]. Last but not the least, prognosis can be markedly improved by early diagnosis and surgical management.…”

Primary Epithelial Neuroendocrine Tumors of the Retroperitoneum

“…6 Overall sensitivity of the octreotide scan is reported to be as high as 90%; however, false negatives (ie, failed detection) may result from various technical issues including small tumor size, or from inadequate expression of somatostatin receptors. 7 CT and magnetic resonance imaging (MRI) are important modalities used in the localization of carcinoid primaries and/or metastases. The median detection rate and sensitivity of CT and/or MRI have been estimated at 80%; detection rates by CT alone vary from 76% to 100%, whereas MRI detection rates vary from 67% to 100%.…”

Clinicopathological features and prognostic factors of colorectal neuroendocrine neoplasms.

“…Widespread endoscopic screening, increased awareness of neuroendocrine histology, and improved data capture likely have contributed to this trend [4,5,[9][10][11]. The most common primary site of colonic NENs is the cecum, followed by sigmoid colon and ascending colon.…”