Pulmonary neuroendocrine cells: Spectrum of diseases and their radiological-pathological correlations

Pulmonary neuroendocrine cells, which constitute a small percentage (0.4%) of airway epithelial cells, play a key role in hypoxia detection, epithelial growth and regeneration, and in lung organogenesis through the synthesis and secretion of amines and peptides. Lesions resulting from pulmonary neuroendocrine cell proliferation range from benign and indolent to malignant and highly aggressive. The recently updated WHO classification of pulmonary neuroendocrine neoplasms includes typical and atypical carcinoid tumours as well as high-grade neuroendocrine carcinomas: large cell neuroendocrine carcinomas and small cell carcinomas. This classification also recognises a condition known as diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) as a distinct entity. Radiologists need to become familiar with these pathologies as the symptoms often lack specificity, and thus imaging plays a crucial role in diagnosis. An understanding of the correlation between the radiological and pathological examinations of these pathologies can enhance our awareness of the wide spectrum of imaging manifestations.