Lung Cancer: An Overview of Introduction, Types, Pathogenesis, Laboratory Diagnosis, Treatment, Prevention, and Keynotes

Introduction

Lung cancer is one of the leading causes of cancer-related deaths worldwide. It arises from the epithelial cells of the bronchial tree or alveoli and is strongly associated with tobacco smoking, although non-smokers may also be affected due to environmental and occupational exposures. Late presentation and aggressive behavior contribute to its high mortality.

Types of Lung Cancer

It is broadly classified based on histology.

1. Non–Small Cell Lung Cancer (NSCLC) (≈85%)
   • Adenocarcinoma – most common, common in non-smokers
   • Squamous cell carcinoma – strongly linked to smoking
   • Large cell carcinoma
2. Small Cell Lung Cancer (SCLC) (≈15%)
   • Highly aggressive
   • Early metastasis
   • Strong association with smoking

Pathogenesis

Lung cancer develops due to genetic damage caused by carcinogens.

• Tobacco smoke contains multiple carcinogenic compounds
• DNA mutations in TP53, EGFR, KRAS, and ALK genes
• Chronic inflammation and epithelial dysplasia
• Uncontrolled cell proliferation and impaired apoptosis
• Tumor invasion, angiogenesis, and metastasis

Laboratory Diagnosis

Specimens

• Sputum
• Bronchial washings/brushings
• Fine-needle aspiration cytology (FNAC)
• Lung biopsy

Diagnostic methods

• Histopathological examination – gold standard
• Cytology (sputum, BAL)
• Immunohistochemistry (TTF-1, p40, synaptophysin)
• Molecular testing (EGFR, ALK, ROS1 mutations)

Imaging support

• Chest X-ray
• CT scan
• PET-CT

Treatment

Depends on the cancer type and stage.

• Surgery (early-stage NSCLC)
• Chemotherapy
• Radiotherapy
• Targeted therapy (EGFR inhibitors, ALK inhibitors)
• Immunotherapy (PD-1/PD-L1 inhibitors)
• Palliative care in advanced disease

Prevention

• Smoking cessation (most effective)
• Avoid passive smoking
• Control air pollution and occupational hazards
• Early screening in high-risk groups (low-dose CT)
• Healthy lifestyle and regular health check-ups

Keynotes

• Leading cause of cancer-related death.
• Smoking is the major risk factor.
• NSCLC is more common than SCLC.
• Molecular testing guides targeted therapy.
• Early diagnosis improves survival.
• Prevention focuses on tobacco control.

Further Readings

1. https://pubmed.ncbi.nlm.nih.gov/35559635
2. https://www.nhs.uk/conditions/lung_cancer
3. https://www.cancer.org/cancer/types/lung_cancer/about/what-is.html
4. https://bcsrj.com/ojs/index.php/bcsrj/article/view/1407
5. https://www.cancer.gov/types/lung/hp/non-small-cell_lung-treatment-pdq
6. https://www.cdc.gov/lung_cancer/treatment/index.html
7. https://www.cdc.gov/lung_cancer/prevention/index.html
8. https://uspreventiveservicestaskforce.org/uspstf/recommendation/lung_cancer-screening
9. https://www.cancer.org/cancer/types/lung_cancer/about/what-is.html
10. https://www.cancer.gov/types/lung/patient-lung-prevention-pdq
11. https://www.cancerresearchuk.org/about-cancer/lung_cancer/stages-types/types
12. https://iconcancercentre.co.uk/conditions/lung_cancer/
13. https://pubmed.ncbi.nlm.nih.gov/17225705
14. https://iasj.rdd.edu.iq/journals/uploads/2025/08/22/cc9d76a7a9d22ba87df05652e59495f1.pdf
15. https://study.com/academy/lesson/lung_cancer-causes-signs-treatments.html
16. https://www.virginiacancer.com/lung_cancer/types-of-lung_cancer
17. https://www.mayoclinic.org/diseases-conditions/lung_cancer/diagnosis-treatment/drc-20374627
18. https://europeanlung.org/en/information-hub/lung-conditions/lung_cancer