About This Page
This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Lung Cancer is a high-yield USMLE Step 2 CK respiratory topic requiring diagnosis plus next-best-step management
- Severity assessment comes first: unstable patients need immediate stabilization before definitive diagnostic workup
- Use US guideline pathways, imaging, physiology, microbiology, pathology, or risk scoring depending on the condition
- Management depends on cause, severity, comorbidities, and risk of complications
- Exam stems often hinge on classic clues, contraindications, and when to escalate to imaging, procedure, or ICU care
Overview
Lung cancer is divided into non-small cell lung cancer and small cell lung cancer. Adenocarcinoma is the most common subtype overall and is common in peripheral lung and in never-smokers. Squamous cell carcinoma is classically central and cavitary and is associated with hypercalcemia. Small cell carcinoma is central, strongly linked to smoking, metastasizes early, and is associated with neuroendocrine paraneoplastic syndromes.
Epidemiology
Lung cancer is the second most commonly diagnosed cancer and the leading cause of cancer death in the United States. Tobacco smoke is the most important risk factor. Other risks include radon exposure, asbestos, occupational carcinogens, air pollution, prior chest radiation, family history, COPD, and pulmonary fibrosis.
Clinical Features
Symptoms
Progressive or acute dyspnea depending on severity and underlying cause
Cough, chest discomfort, fatigue, or exercise limitation
Fever, weight loss, night sweats, or hemoptysis when infection or malignancy is present
Syncope, confusion, severe hypoxemia, or rapidly worsening respiratory distress
Symptoms may be absent when the condition is detected incidentally
Signs
Abnormal breath sounds, crackles, wheeze, dullness, or reduced air entry depending on pathology
Tachypnea, tachycardia, or oxygen desaturation when clinically significant
Cyanosis, hypotension, altered mental status, or respiratory exhaustion
Clubbing, lymphadenopathy, cachexia, or signs of chronic disease when present
Physical examination can be normal in early or mild disease
Investigations
First-line
Chest CT with contrastDefines mass, lymph nodes, mediastinal involvement, pleura, and local invasion
Tissue diagnosisBronchoscopy for central lesions; CT-guided biopsy for peripheral lesions; thoracentesis cytology if pleural effusion is present
Low-dose CT screeningAnnual LDCT for eligible high-risk adults; screening is not chest X-ray
Second-line
PET-CTStaging for suspected NSCLC and evaluation of metabolically active nodes or metastases
Brain MRIFor stage II or higher NSCLC, neurologic symptoms, or any small cell lung cancer staging depending on protocol
Molecular testingEGFR, ALK, ROS1, BRAF, MET, RET, NTRK, KRAS, PD-L1 and other markers guide targeted therapy and immunotherapy in advanced NSCLC
Specialist
Specialist referralPulmonology, infectious disease, oncology, sleep medicine, critical care, or thoracic surgery depending on diagnosis and severity
Advanced testingBronchoscopy, PET-CT, sleep study, HRCT, echocardiography, or interventional radiology procedures when indicated
1
Initial management
- Assess severity, oxygenation, hemodynamics, airway risk, and need for hospital or ICU care
- Treat immediately reversible threats such as hypoxemia, bronchospasm, sepsis, PE, pneumothorax, or respiratory failure
- Use diagnosis-specific guideline therapy rather than empiric escalation without a working differential
2
Definitive treatment
- Treat the underlying cause according to US guideline recommendations
- Use imaging, microbiology, pathology, physiology, and risk stratification to guide therapy
- Escalate to procedural or specialist management when medical therapy is insufficient or diagnosis remains uncertain
3
Follow-up and prevention
- Arrange follow-up imaging or functional testing when recommended
- Address smoking cessation, vaccination, occupational exposure, medication toxicity, and comorbidity optimization
- Educate patients on red flags including worsening dyspnea, hemoptysis, syncope, hypoxemia, or persistent fever
Complications
- Respiratory failure: Severe disease can progress to hypoxemia, hypercapnia, or need for ventilatory support
- Secondary infection: Damaged or obstructed lung is prone to bacterial infection
- Pulmonary hypertension: Chronic hypoxemia or parenchymal disease can increase pulmonary vascular resistance
- Delayed diagnosis: Incidental or nonspecific presentations may hide malignancy, TB, PE, or ILD
- Treatment toxicity: Antimicrobials, corticosteroids, anticoagulants, chemotherapy, or procedures can cause harm
USMLE Step 2 CK Exam Tips
- 1Adenocarcinoma is the most common lung cancer overall and the most common in never-smokers; usually peripheral
- 2Squamous cell carcinoma is central, can cavitate, and causes hypercalcemia via PTHrP
- 3Small cell carcinoma causes SIADH, ectopic ACTH, and Lambert-Eaton; it is treated primarily with chemotherapy/radiation, not surgery
- 4Pancoast tumor = apical lung cancer + shoulder/arm pain + Horner syndrome
- 5Screening test is low-dose CT, not chest X-ray or sputum cytology
- 6Recurrent pneumonia in the same lobe in an older smoker = obstructing lung cancer
- 7Finger clubbing and hypertrophic osteoarthropathy are classically associated with lung cancer
practicetest your knowledge on lung cancerApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — respiratory and beyond.
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