Nearly half of all lung cancers are adenocarcinomas falling into various subtypes. Other common types of lung cancer include squamous cell carcinoma and small cell carcinoma. The pathogenesis and molecular biology of lung cancer has been the subject of considerable research over the last few years, and new pharmacologic therapies have been developed. The histological classification of lung adenocarcinomas has been revised in 2011, and is already becoming established in replacing the WHO classification. The aim of the new classification is to make the diagnostics of lung cancer and assessment of treatment options more precise.