A chest X-ray is always indicated, and a shadow caused by the tumour may often be seen, as marked ‘Ca’ here, or lymph involvement may indicate the presence of a tumour. The development of shadowing on an X-ray often lags behind formation of the cancer and a lesion has to be over a centimetre in diameter before it can be recognised. Thus a negative chest X-ray does not exclude cancer. CT scanning resolves smaller lesions and is commonly used for more accurate diagnosis and staging or when metastases are suspected. MRI⁴⁵ and PET⁴⁶ scanning have also been suggested, but are not feasible in routine diagnosis. Rigid Bronchoscopy is used to assess for tumours high up the bronchial tree. Bronchoscopy using fibre-optic equipment can visualise the lesion in about 70% of cases. Cytological examination of cells in sputum, pleural effusions or bronchoalveolar lavages may aid in diagnosis of malignancy, indicating the need for further tests, these tests have the advantage of being of low-invasion. Biopsy either by Transthoracic Needle Aspiration Biopsy (TNAB) or less commonly surgically is effective at giving an accurate diagnosis of tumour type and grade of abnormality.⁴⁷

Mediastinoscopy is a common procedure used for the diagnosis and in particular staging of lung cancer.⁴⁸ Though several techniques have been described, mediastinoscopy usually involves passing a telescopic instrument through an incision in the suprasternal notch allowing the surgeon to examine lymph nodes draining the lungs. The procedure is only able to access the paratracheal, tracheobronchial and subcarinal nodes, but is not able to reach the posterior subcarinal nodes, subaortic nodes and pulmonary ligament nodes.⁴⁸

This procedure is associated with a comparatively high rate of morbidity and occasional mortality. The role of this procedure is continually being evaluated as less invasive imaging techniques such as PET scanning are developing and improving.

Fluorescence bronchoscopy is being developed as a means of detecting lung cancer at an earlier stage, to enable more effective treatment. Currently the systems available have poor sensitivity and specificity, but there is potential for development.⁴⁹