Pulmonary neuroendocrine neoplasms: the molecular landscape, therapeutic challenges, and diagnosis and management strategies.

Lung neuroendocrine neoplasms are a group of diverse, heterogeneous tumours that range from well-differentiated, low-grade neuroendocrine tumours-such as typical and atypical carcinoids-to high-grade, poorly differentiated aggressive malignancies, such as large-cell neuroendocrine carcinoma (LCNEC) and small-cell lung cancer (SCLC). While the incidence of SCLC has decreased, the worldwide incidence of other pulmonary neuroendocrine neoplasms has been increasing over the past decades. In addition to the standard histopathological classification of lung neuroendocrine neoplasms, the introduction of molecular and sequencing techniques has led to new advances in understanding the biology of these diseases and might influence future classifications and staging that can subsequently improve management guidelines in the adjuvant or metastatic settings. Due to the rarity of neuroendocrine neoplasms, there is a paucity of prospective studies that focus on the lungs, especially in rare, well-differentiated carcinoids and LCNECs. In contrast with the success of targeted therapies in non-small-cell lung cancer (NSCLC), high-grade neuroendocrine carcinomas of the lung often only have a few specific targetable gene alterations. Optimal therapy for LCNECs is not well defined and treatment recommendations are based on extrapolating guidelines for the management of patients with SCLC and NSCLC. This Review explores the epidemiology, diagnosis, and staging of lung neuroendocrine neoplasms to date. In addition, we focus on the evolving molecular landscape and biomarkers, ranging from tumour phenotypes to functional imaging studies and novel molecular biomarkers. We outline the various clinical outcomes, challenges, the treatment landscape, ongoing clinical trials, and future directions.