31st December 2024

Pathology of lung cancer

Lung cancer has been classically divided into small cell and non-small cell types. Small cell lung cancers (SCLC) account for approximately 20% of all cases, whilst the majority are non-small cell lung cancers (NSCLC). ‘NSCLC’ is a blanket term comprising a variety of histological types including adenocarcinoma (approximately 40% of cases), squamous cell carcinoma (SCC, approximately 30%), large cell carcinoma, and other rarer histological types.

Adenocarcinoma of the lung is the most common histological type both overall and in non-smokers. Adenocarcinomas usually arise in the lung periphery. By comparison, SCCs typically arise centrally and cavitation may be another distinguishing feature. SCLCs are aggressive tumours arising from neuroendocrine cells, typically of the larger airways. SCLCs tend to carry a worse prognosis and a majority of patients already have distal metastases at the time of diagnosis (de novo metastatic disease).

Common sites of lung cancer metastasis include the adrenal glands, bone, brain, liver and other parts of the lung.