Lung cancer !
Lung cancer is a malignant tumour that starts in the lining of the airways or air sacs; it is grouped as small cell or non-small cell cancer.
Updated 2026-10-30
Structures involved
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- Right upper lobe
- Left upper lobe
- Main bronchi
- Lobar bronchi
- Mediastinal lymph nodes
- Pleura
- Superior vena cava
- Recurrent laryngeal nerves
- Sympathetic trunk
- Phrenic nerves
In biochemistry
In immunology
In histology
In the clinical exam
- Digital clubbing and nail signs
- Medicines, allergies and habits: tobacco, alcohol and other substances
- Respiratory symptoms: cough, sputum, hemoptysis and dyspnea
- Consolidation syndrome
- Pleural effusion syndrome
- Atelectasis syndrome
- Cavitation syndrome
In physiology
Why it happens
- Oncogenes: RAS, MYC, HER2, BCR-ABL and the table to know
- Chemical carcinogens: initiation, promotion and the table to know
- Tobacco: how smoking injures tissue
- Molecular pathology: PCR, FISH, sequencing and liquid biopsy
- Invasion and metastasis: the metastatic cascade, step by step
- The hallmarks of cancer
Show 16 more
- Paraneoplastic syndromes: the table to know
- Local effects of tumours and cancer cachexia
- How tumours evade the immune system
- From specimen to report: fixation, margins and the pathology report
- Evading cell death and replicating without limit: BCL2 and telomerase
- Grading and staging: what TNM means
- Air pollution and occupational exposures
- Metaplasia
- Cancer epidemiology: age, environment, predisposing conditions (and Colombia)
- Immunohistochemistry: the principle and the markers to know
- Tumour angiogenesis
- Pathways of spread and the usual metastatic sites
- Translocations, amplifications and epigenetic changes in cancer
- Frozen section: the intraoperative consultation
- Cytology: the Pap test, fine-needle aspiration and body fluids
- Radiation and cancer: ultraviolet and ionizing
What it is
Malignant tumour arising from the bronchial or alveolar epithelium, divided into non-small cell lung cancer (most cases) and small cell lung cancer.
Who gets it
A leading cause of cancer death worldwide, usually diagnosed late. In Colombia and Latin America tobacco is the main cause, but household smoke from wood or other biomass used for cooking also contributes, especially in rural women. National claims data estimated a prevalence of 11.14–18.05 per 100,000 inhabitants in Colombia in 2017–2019.
Causes
- Tobacco smoking (main cause; risk rises with pack-years)
- Second-hand smoke
- Indoor smoke from biomass fuels (wood, coal) used for cooking or heating
- Radon, asbestos and other occupational carcinogens
- Air pollution
- Driver mutations (e.g. EGFR, ALK), more common in never-smokers with adenocarcinoma
Risk factors
- Current or former smoking
- Older age
- COPD and pulmonary fibrosis
- Family history of lung cancer
- Occupational or household exposure to carcinogens or biomass smoke
- Previous chest radiation
Pathophysiology
Repeated carcinogen exposure causes cumulative genetic damage in airway epithelium, progressing from dysplasia to invasive cancer. Central tumours obstruct bronchi; peripheral ones invade the pleura and chest wall. Spread is to mediastinal nodes, brain, bone, liver and adrenals; some tumours secrete hormones that cause paraneoplastic syndromes.
Classification
- Non-small cell (NSCLC): adenocarcinoma (most common, peripheral), squamous cell (central, smoking), large cell
- Small cell (SCLC): central, aggressive, early spread, strongly linked to smoking
- TNM staging guides treatment; SCLC is often described as limited or extensive
Symptoms and signs
- Persistent cough or change in a chronic cough
- Haemoptysis
- Breathlessness, chest pain, weight loss and fatigue
- Hoarseness (recurrent laryngeal nerve involvement)
- Recurrent pneumonia in the same lobe
- Finger clubbing
Diagnosis
- Clinical
- Suspected from symptoms in at-risk people or from an incidental nodule. Paraneoplastic syndromes may appear first: SIADH and Cushing syndrome (small cell), hypercalcaemia (squamous), Lambert-Eaton syndrome.
- Tests
- Tissue diagnosis by bronchoscopy, CT-guided or EBUS-guided biopsy; molecular testing for targetable mutations and PD-L1 in NSCLC. Calcium, sodium and liver tests; lung function before surgery.
- Imaging
- Chest X-ray then contrast CT of chest and upper abdomen; PET-CT and brain MRI for staging. Low-dose CT screening is offered to selected heavy smokers in some guidelines; criteria vary.
Differential diagnosis
- Pulmonary tuberculosis
- Community-acquired pneumonia or lung abscess
- Benign lung nodule or granuloma
- Lung metastases from another primary
- Lymphoma or other mediastinal mass
Goal of treatment
Cure localised disease where possible, and otherwise prolong survival and relieve symptoms, guided by stage, histology, molecular profile and fitness.
Treatment
- Surgical
- Surgical resection (lobectomy with lymph node sampling) for early-stage NSCLC in fit patients.
- Medical
- Chemotherapy, often combined with radiotherapy; platinum-based combinations are the standard for SCLC.
- Medical
- Targeted therapies (e.g. tyrosine kinase inhibitors for EGFR or ALK changes) and immune checkpoint inhibitors in selected NSCLC.
- Procedure
- Radiotherapy, including stereotactic radiotherapy for early tumours in patients unfit for surgery, and palliative radiotherapy for symptoms.
- Conservative
- Palliative care from diagnosis for pain, breathlessness and quality of life.
- Lifestyle
- Smoking cessation at any stage.
Drugs for this condition
Complications
- Malignant pleural effusion
- Superior vena cava obstruction
- Post-obstructive pneumonia and haemoptysis
- Brain, bone, liver and adrenal metastases
- Paraneoplastic syndromes (SIADH, hypercalcaemia, Lambert-Eaton)
- Recurrent laryngeal or phrenic nerve palsy
Prognosis
Strongly stage-dependent: early resected NSCLC can be cured, but most patients present with advanced disease. SCLC responds initially to treatment but usually relapses. Targeted therapy and immunotherapy have improved survival in selected patients.
Prevention
- Not smoking and quitting at any age
- Cleaner cooking fuels and good ventilation to reduce household smoke
- Workplace protection against asbestos and other carcinogens
- Low-dose CT screening of eligible high-risk people where programmes exist
Test yourself
Think of the answer, then tap the question to see it.
What are the two main histological groups of lung cancer?
Non-small cell lung cancer (adenocarcinoma, squamous, large cell) and small cell lung cancer.
Which paraneoplastic syndromes are classically linked to small cell lung cancer?
SIADH (hyponatraemia), ectopic ACTH (Cushing syndrome) and Lambert-Eaton myasthenic syndrome.
Which lung cancer type classically causes hypercalcaemia?
Squamous cell carcinoma, through PTH-related peptide.
What is a Pancoast tumour and how does it present?
A lung apex tumour invading the brachial plexus and sympathetic chain: shoulder and arm pain, hand weakness and Horner syndrome.
Which imaging test is used to screen selected heavy smokers for lung cancer?
Low-dose CT of the chest, offered to eligible high-risk people; criteria vary by guideline.
Related conditions
- Chronic obstructive pulmonary disease (COPD)
- Pulmonary tuberculosis
- Pleural effusion
- Community-acquired pneumonia
- Thoracic outlet syndrome
- Interstitial lung disease
- Oesophageal cancer
- Laryngeal cancer
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Non–Small Cell Lung Cancer (StatPearls (NCBI Bookshelf), 2023); Small Cell Lung Cancer (StatPearls (NCBI Bookshelf), 2026); Prevalence of lung cancer in Colombia and a new diagnostic algorithm using health administrative databases: A real-world evidence study (PloS one, 2023) · adapted, CC BY 4.0.
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Representative model, for educational purposes only.
