Neuroendocrine tumors, such as carcinoid tumors, overexpress somatostatin receptors in their membranes. Octreotide is an analogue whose molecule is a shortened version of somatostatin's with a high affinity for these receptors. The labelled form of octreotide is able to be imaged in scans (Octreoscan) and, therefore, pathological conditions overexpressing somatostatin receptors are easily recognized in this technique. Specifically, in the case of the detection of carcinoid tumors, the Octreoscan has sensitivity nearly to 90%.
A research article to be published on September 14, 2008 in the World Journal of Gastroenterology addresses this question. The research team led by Alberto Fernandez from POVISA Hospital in Spain presents a case of a patient with a high suspicious of ileal carcinoid tumor (according to CT-scan and colonoscopy results) with a positive Octreoscan, showing uptake in the same bowel reported as pathological in CT. The patient underwent surgery and histological analysis reported Crohn's disease.
This article is the second report of CD a cause of false positive in octeotride scan. In order to explain this abnormal uptake, immunohistochemical studies were performed but the authors did not find somatostatine receptors in the sample. In the previous report published of CD mimicking an ileal carcinoid there is no evidence that somatostatin receptors were determined.
The authors did not find any explanation, and concluded encouraging physicians to be aware of CD as a cause of false positive results of Octreoscan and that further studies should be made in order to assess the possible causes of this abnormal uptake.
Source: World Journal of Gastroenterology