Lung cancer

Last revised by Calum Worsley on 18 Feb 2024

Primary lung cancer is a broad term referring to the main histological subtypes of primary lung malignancies that are mainly linked with inhaled carcinogens, with tobacco smoke being a key risk factor. 

This article will broadly discuss all the histological subtypes as a group, focussing on their common aspects; for further details please refer to the specific articles on each subtype described below. 

Bronchogenic carcinoma is a term that is frequently used as a synonym for lung cancer although is not strictly accurate, in that lung cancers can arise from the lung parenchyma and not just the airways 17.

Lung cancer is a leading type of cancer, equal in prevalence to breast cancer 13. It is the leading cause of cancer mortality worldwide; accounting for ~20% of all cancer deaths 1.

The major risk factor is tobacco smoking, which is implicated in 90% of cases and increases the risk of lung cancer (by histological subtype) 10:

  • squamous cell lung cancer: 11x (men), 15x (women)

  • small cell lung cancer: 10x (men), 25x (women)

  • large cell lung cancer: 7x (men), 8x (women)

  • lung adenocarcinoma: 4x (men and women)

Other risk factors:

Various paraneoplastic syndromes can arise in the setting of lung cancer:

Patients with lung cancer may be asymptomatic in up to 50% of cases. Cough and dyspnea are rather non-specific symptoms that are common amongst those with lung cancer.

Central tumors may result in hemoptysis and peripheral lesions with pleuritic chest pain.

Pneumonia, pleural effusion, wheeze, lymphadenopathy are not uncommon. Other symptoms may be secondary to metastases (bone, contralateral lung, brain, adrenal glands, and liver, in frequency order for NSCLC 12) or paraneoplastic syndromes.

The term bronchogenic carcinoma is somewhat loosely used to refer to primary malignancies of the lung that are associated with inhaled carcinogens 1 and includes four main histological subtypes. These are broadly divided into non-small cell carcinoma and small cell carcinoma as they differ clinically regarding presentation, treatment, and prognosis:

Other malignant pulmonary neoplasms include lymphoma and sarcoma (rare).

Each subtype has different radiographic appearances, demographics, and prognoses:

Several antibodies or markers from tissue samples may be useful in the diagnosis and prognostication of disease. These include

  • ROS1 mutation: 1-2% of NSCLC 15; more common in females 14

  • ALK mutation: 2-5% of NSCLC; more common in males, younger, light/never smokers, and more likely to be adenocarcinoma presenting with advanced disease 16 (see: main article)

Treatment and prognosis vary not only with stage but also with cell type. In general, surgery, chemotherapy, and radiotherapy are offered according to the stage, resectability, operability, and functional status. Targeted treatments depend on molecular testing, e.g. ALK mutated lung cancers can be treated with ALK-inhibitors (e.g. crizotinib) 16.

  • treatment

    • operable disease (stage I to IIIA): surgery

    • unresectable disease: neoadjuvant chemotherapy, radiotherapy

    • advanced disease: palliative combined chemotherapy

  • prognosis (5-year survival rates):

    • local (stage I): 55-67%

    • locally advanced (stages II-IIIA): 23-40%

    • advanced (stages IIIB and IV): 1-3%

  • treatment

    • limited disease: chemoradiotherapy

    • extensive disease: palliative combined chemotherapy

  • prognosis: poor

    • limited: 5-year survival rate 15-25%

    • extensive: 2-year survival 20% (with palliative combined chemotherapy and supportive care)

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