Diagnosis and prevention

Performing a chest x-ray is the first step if a patient reports symptoms that may be suggestive of lung cancer. This may reveal an obvious mass, widening of the mediastinum (suggestive of spread to lymph nodes there), atelectasis (collapse), consolidation (pneumonia), or pleural effusion. If there are no x-ray findings but the suspicion is high (such as a heavy smoker with blood-stained sputum), bronchoscopy and/or a CT scan may provide the necessary information. Bronchoscopy or CT-guided biopsy is often used to identify the tumor type.

The main causes of lung cancer (and cancer in general) include carcinogens (such as those in tobacco smoke), ionizing radiation, and viral infection. This exposure causes cumulative changes to the DNA in the tissue lining the bronchi of the lungs (the bronchial epithelium). As more tissue becomes damaged, eventually a cancer develops.

Symptoms that suggest lung cancer include:^[27]

• dyspnea (shortness of breath)

• hemoptysis (coughing up blood)

• chronic coughing or change in regular coughing pattern

• wheezing

• chest pain or pain in the abdomen

• cachexia (weight loss), fatigue and loss of appetite

• dysphonia (hoarse voice)

• clubbing of the fingernails (uncommon)

• dysphagia (difficulty swallowing).

The vast majority of lung cancers are carcinomas—malignancies that arise from epithelial cells. There are two main types of lung carcinoma, categorized by the size and appearance of the malignant cells seen by a histopathologist under a microscope: non-small cell (80.4%) and small-cell (16.8%) lung carcinoma. This classification, based on simple histological criteria, has important implications for clinical management and prognosis of the disease.