The molecular pathogenesis and management of bronchial carcinoids

INTRODUCTION: In terms of well-differentiated neuroendocrine tumors (NETs), the lung is the second most common site of occurrence, after the gastro-entero-pancreatic axis, and comprises ～ 25% of all NETs which may occur in various parts of the body. Pulmonary NETs are classified into four groups including typical carcinoid tumors, atypical carcinoid tumors, small cell lung carcinoma and large cell neuroendocrine carcinomas. Among pulmonary NETs, typical and atypical carcinoid tumors of the lung are generally indolent, but do have a (albeit low) potential to metastasize. AREAS COVERED: The molecular biology and novel molecular pathways and drug targets in bronchial carcinoids are reviewed in this paper. A full data search is performed through PubMed over the years 2000 - 2010 with key words 'neuroendocrine tumors of the lung, bronchial carcinoid, lung carcinoid, foregut carcinoid, pulmonary carcinoid, pulmonary NETs, lung NETs, molecular biology, autoradiography, nuclear medicine, treatment'; all relevant publications are included, together with selected publications prior to that date. EXPERT OPINION: Although lying at the benign end of the spectrum of pulmonary NETs, bronchial carcinoids can metastasize, and the pathogenesis of these tumors is poorly understood. Several intracellular signaling pathways are under investigation to define new targets for the successful treatment of these tumors. In terms of treatment, further research should additionally focus on the already known but promising drug options.