Typical lung carcinoids: review of classification, radiological signs and nuclear imaging findings

Purpose: In this comprehensive review we present an overview of the main aspects of classification, radiological signs and nuclear imaging findings of typical lung carcinoids (TCs). Methods: A literature search on the PubMed literature database was conducted using the terms “positron emission tomography—PET”, “PET/CT”, “FDG”, “18F-fluorodeoxyglucose”, “MDCT—Contrast-enhanced multi-detector computed tomography” “typical lung carcinoid” “SRS—Somatostatin receptor scintigraphy”, “68 Ga DOTA-peptides” alone and in combination, extending until December 2019. Results: TCs are rare tumours, accounting for only 1–2% of all pulmonary neoplasms. They tend to occur usually in the fourth-to-sixth decade of life and are characterized by mitotic count of less 2/2 mm2 and absent necrosis. Contrast-enhanced multi-detector computed tomography (MDCT) is the most largely used imaging modality for the localization, characterization and staging of lung TCs. Nuclear medicine imaging assists MDCT in the diagnosis of these rare tumour entities, especially by somatostatin receptor scintigraphy, PET imaging with Gallium-68-tetrazacyclododecanetetraacetic acid (68 Ga DOTA-peptides) and with 18F-fluorodeoxyglucose (18F-FDG). Conclusions: TCs of lung are rare lung tumours placed within a defined classification system. MDCT morphological features combined with functional nuclear medicine imaging are an important tool for the detection of these rare neoplasms and contribute to their characterisation and staging. Therefore, MDCT and nuclear medicine parameters could give a preliminary orientation before the pathological examination, on the biological behaviour and the prognostic outcome of TCs.