Chest ImagingLung cancer
(also called bronchogenic
carcinoma), by far the most common fatal
malignant neoplasm in men and it has now surpassed breast cancer as the leading cause of cancer death in women. Most lung cancer deaths are directly attributable to cigarette smoking. The risk of lung cancer occurrence is related to the number of cigarettes smoked, the number of smoking years, the age at which smoking began, and the depth of inhalation. The risk decreases with cessation of smoking but never completely disappears.
Other aetiological factors including genetic and occupational factors and the presence of concomitant disease in the lung may play a role in the development of lung cancer. Among the occupational agents that may increase the risk of lung cancer, asbestos is the most important. A combination of asbestos exposure and cigarette smoking has been proved to multiply the risk of lung cancer, particularly if asbestosis is present in the lung parenchyma. The other occupation agents associated with lung cancer include arsenic, coke, chromium, chloromethyl ether and mustard gas. The concomitant lung diseases associated with lung cancer usually reflect the presence of fibrosis in the lung. They include any cause of end-stage lung disease such as idiopathic pulmonary fibrosis or progressive systemic sclerosis and localizing fibrosing disease such as tuberculosis.
Most patients with lung cancer present with clinical symptoms, and only a minority are asymptomatic. Patients with central tumours obstructing a major bronchus may present with cough, wheezing, haemoptysis and lung infection. Local intrathoracic spread may result in left laryngeal nerve paralysis, pleural or chest wall pain, symptoms related to superior vena cava obstruction or Pancoasts neoplasm. Sometimes symptoms resulting from distant metastases may reveal the lung cancer. A large variety of paraneoplastic syndromes may also be associated with lung cancer. They include skeletal abnormalities such as clubbing, hypertrophic pulmonary osteoarthropathy (see osteoarthropathy) and osteomalacia or endocrine and metabolic disorders such as Cushing's syndrome from adenocorticotrophic hormone (ACTH) production, hyponatraemia associated with inappropriate antidiuretic hormone (ADH) syndrome production, and insulin-like activity. A variety of neurological paraneoplastic syndromes may occur including neuromuscular dysfunction, carcinomatous myopathy, peripheral neuropathies, subacute cerebellar degeneration and encephalomyelopathy. Other paraneoplastic syndromes include various haematological, dermatological and vascular disorders, such as a migratory thrombophlebitis and arterial thrombosis.
Histologically, the common cell types of lung cancers include adenocarcinoma pulmonary, squamous cell carcinoma pulmonary, small cell carcinoma and large cell undifferentiated carcinoma. Multidifferentiated carcinomas may also occur (adenosquamous carcinoma). Giant cell carcinoma is a subset of large-cell undifferentiated carcinoma. Bronchioalveolar cell carcinomatosis is a subset of adenocarcinoma.
The radiological appearances of lung cancer depend on the location of Signs of intrathoracic spread include bone destruction, pleural effusion, hilar and mediastinal lymphadenopathy, lung nodule in the contralateral lung, mediastinal mass, or pleural nodularity or nodular thickening of the interlobular septa (see Pancoasts neoplasm, lymphangitic carcinomatosis). For classification and staging of lung cancer, see lung cancer staging, lung cancer stage grouping and lung cancer TNM classification.
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