Diagnostic imaging of neuroendocrine tumours

Neuroendocrine tumours (NET) consists of a heterogeneous group of neoplasms, that are able to express cell membrane neuroamine uptake mechanisms and/or specific receptors, such as somatostatin receptors, which can be used in the localization and treatment of these tumours. Conventionally NETs may present with a wide variety of functional or nonfunctional endocrine syndromes and may be familial and have other associated tumors, also they have different histology pattern and prognosis. They originate from endocrine glands such as the pituitary, the parathyroids, and the (neuroendocrine) adrenal, as well as endocrine islets within glandular tissue (thyroid or pancreatic) and cells dispersed between exocrine cells, such as endocrine cells of the digestive system (gastroenteropancreatic GEP-NET) and respiratory tracts. GEP-NET are the most common including more then 70% of all NETs. Imaging modalities and assessment of specific tumor markers offers high sensitivity in establishing the diagnosis and can also have prognostic significance. Most important single imaging technique in terms of initial identification and staging of GEP-NET seems to be somatostatin receptor scintigraphy (SRS). Other investigations like helical computed tomography (CT), magnetic resonance imaging (MRI), endoscopic and/or peri-operative ultrasonography are used for the precise localization of NET. Another one functional approach include MIBG (meta-iodobenzylguanidine scintigraphy). This technique is sensitive in the identification of chromaffin cell tumours pheochromocytoma, and also medullary thyroid carcinoma (MTC), although SRS seems to be very useful in the localization of malignant chromaffin cell tumours and MTC as well. The further localization and monitoring of the response to treatment CT, SRS and MRI are used with high diagnostic accuracy. More recently, positron emission tomography (PET) scanning is being increasingly used for the localization of NETs, due to develop new PET tracers (Ga-68), the standard one FDG PET is currently used in groups of high malignant NET.