Carcinoid and Other Lung Neuroendocrine Tumour: An Update
Dr Teo Yin Keong, Gleneagles Hospital Medini Johor

Well-differentiated lung neuroendocrine (bronchial carcinoid) tumours (NETs) are a rare group of pulmonary neoplasms that are often characterized by indolent clinical behaviour. Like other carcinoid tumours, lung NETs are thought to derive from peptide- and amine-producing neuroendocrine cells. NETs can arise from many sites in the body, including the thymus, lung, gastrointestinal (GI) tract, and ovary. The GI tract is the most frequently involved site for NETs, while the lung is the second most common.

Lung NETs are characterized by strikingly heterogeneous pathological features and clinical behaviour. At one end of the spectrum are the so-called typical carcinoids, which are well-differentiated, low-grade, slowly growing neoplasms that seldom metastasize to extrathoracic structures. At the other end of the spectrum are the poorly differentiated and high-grade neuroendocrine carcinomas, as typified by small cell lung cancer, which behaves aggressively, with rapid tumour growth and early distant dissemination. The biologic behaviour of intermediate-grade (atypical) NETs, which are of intermediate grade and differentiation, is intermediate between low-grade NETs and small cell lung cancer. The terms "typical" and "atypical" carcinoid of the lung correspond roughly to the terms "grade 1" and "grade 2," which are used more commonly in extra-thoracic NETs.

The treatment and prognosis of both low-grade (typical) and intermediate-grade (atypical) lung NETs (carcinoid tumours) will be discussed here.