Lung Cancer: An Overview of Introduction, Types, Pathogenesis

Introduction

Table of Contents

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.

Non–Small Cell Lung Cancer (NSCLC) (≈85%)
- Adenocarcinoma – most common, common in non-smokers
- Squamous cell carcinoma – strongly linked to smoking
- Large cell carcinoma
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

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.

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