Lung cancer has increased in incidence throughout the twentieth century and is 
now the most common cancer in the Western World. It has a poor prognosis, only 
10-15% of patients survive 5 years or longer. Outcome is dependent on clinical 
stage and cancer cell type. Lung cancer is broadly subclassified on the basis of 
histological features into squamous cell carcinoma, adenocarcinoma, large cell 
carcinoma and small cell carcinoma. The histopathological type of lung cancer 
correlates with tumour behaviour and prognosis. Staging based on prognosis is 
essential in clinical trials comparing different management strategies, and 
enables universal communication regarding the efficacy of different treatments 
in specific patient groups. The anatomic extent of disease determined either 
preoperatively using imaging supplemented by invasive procedures such as 
mediastinoscopy, and anterior mediastinotomy or following resection are 
described according to the T-primary tumour, N-regional lymph nodes, M-distant 
metastasis classification. The International System for Staging Lung Cancer 
attempts to group together patients with similar prognosis and treatment 
options. Various combinations of T, N, and M define different clinical or 
surgical-pathological stages (IA-IV) characterised by different survival 
characteristics. Refinements in staging based on imaging findings have enabled 
clinical staging to more accurately reflect the surgical-pathological stage and 
therefore more accurately predict prognosis. Recent advances including the use 
of positron emission tomography in combination with conventional staging 
promises to increase the accuracy of staging and therefore to reduce the number 
of invasive staging procedures and inappropriate thoracotomies.