E1102. Spectrum of Pulmonary Neuroendocrine Proliferations and Neoplasms: A Pictorial Review
  1. Selima Siala; University of North Carolina at Chapel Hill
  2. Muthu Sakthivel; University of North Carolina at Chapel Hill
  3. Nabil Rahoui; University of North Carolina at Chapel Hill
  4. Todd Hazelton; University of North Carolina at Chapel Hill
Neuroendocrine cells are normally present in the mucosa of bronchial and bronchiolar epithelium where they can be found singly or in clusters. They produce, store, and secrete amines and peptides and serve as chemoreceptors for detecting hypoxia. Therefore, reactive pulmonary neuroendocrine cell (PNEC) hyperplasia and proliferation can occur in response to chronic hypoxia or airway inflammation. However, these can also occur in the absence of predisposing factors. This variety of PNEC proliferations manifest with a wide range of imaging abnormalities.

Educational Goals / Teaching Points
Review the spectrum of neuroendocrine lung lesions. Illustrate the typical radiological and pathological appearance of neuroendocrine proliferations and neoplasm.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The clinical and radiological presentation of PNEC proliferations varies depending on the pathological basis of the lesions. One notable condition within this spectrum is diffuse idiopathic neuroendocrine cell hyperplasia (DIPNECH), a diffuse form of neuroendocrine cell hyperplasia confined to the epithelial basement membrane of the airway. DIPNECH is considered a preinvasive lesion that may give rise to carcinoid tumors. Predominantly affecting older women, it can be asymptomatic or present with chronic respiratory symptoms. High-resolution chest CT imaging in DIPNECH can demonstrate pulmonary micronodules with or without associated mosaic attenuation or air trapping on expiratory CT. Carcinoid tumors, on the other hand, are low-grade malignant neoplasms that primarily affect symptomatic children and young adults. Typical and atypical carcinoids have similar imaging features and usually appear as well-defined pulmonary nodules or masses, often in close proximity to central bronchi, and may exhibit calcification and contrast enhancement. While typical carcinoids have a favorable prognosis, atypical carcinoids are aggressive malignancies with a propensity for metastasis. The spectrum also includes highly aggressive neuroendocrine malignancies such as large cell neuroendocrine carcinoma of the lung and small cell lung carcinoma, typically found in elderly smokers. These malignancies present as large peripheral or central pulmonary masses and are frequently accompanied by local invasion, intrathoracic lymphadenopathy, and distant metastases at the time of diagnosis.

Pulmonary neuroendocrine proliferations and neoplasms arise from cells that normally line the respiratory tract mucosa and result in a broad range of clinical and imaging presentations but may be completely asymptomatic. Radiologists play an important role in the characterization of these entities and may be the first to suggest the correct diagnosis.