13. CANCER

Cancer is an abnormal and uncontrolled growth of cells forming a mass called a tumor or neoplasm. Unlike normal cells, cancer cells grow without control, do not respond to normal regulatory signals, and continue multiplying even when the stimulus stops. Tumors may be:

  • Benign (noncancerous) – slow growing, localized, and less harmful.
  • Malignant (cancerous) – fast growing, invasive, and able to spread.

The study of tumors is called oncology.

Classification of Cancer

1. Based on Site of Origin

Examples:

  • Breast cancer
  • Lung cancer
  • Prostate cancer
  • Liver cancer
  • Kidney cancer
  • Oral cancer
  • Brain cancer

2. Based on Tissue Type

  • Carcinoma: From epithelial tissue; accounts for 80–90% of cancers (breast, lung, prostate, colon).
  • Sarcoma: From connective tissues—bone (osteosarcoma), cartilage, fat, muscle.
  • Myeloma: Cancer of plasma cells in bone marrow.
  • Leukemia: Cancers of bone marrow producing abnormal WBCs.
  • Lymphoma: Cancers of lymphatic tissues; Hodgkin and Non-Hodgkin types.
  • Mixed types: Tumors containing more than one tissue type (e.g., carcinosarcoma).

3. Based on Grade

  • Grade 1: Well differentiated, mildly abnormal.
  • Grade 2: Moderately differentiated.
  • Grade 3: Poorly differentiated.
  • Grade 4: Undifferentiated, most aggressive.

4. Based on Stage – TNM System

  • T: Size of primary tumor.
  • N: Spread to lymph nodes.
  • M: Distant metastasis.

Etiology (Causes of Cancer)

Cancer develops due to mutations in DNA. These mutations may be inherited or acquired.

1. Host Factors

  • Age (risk increases with age)
  • Sex (some cancers are hormone-related)
  • Genetic background (inherited gene mutations)
  • Immune suppression (HIV, transplant patients)

2. Environmental and Lifestyle Factors

  • Smoking (major cause of lung cancer)
  • Diet high in red meat and low in fibre
  • Alcohol consumption
  • Obesity and lack of exercise
  • Occupational exposures (chemicals, asbestos)

3. Infections

  • Hepatitis B and C → liver cancer
  • HPV → cervical cancer
  • EBV → Burkitt lymphoma, nasopharyngeal carcinoma
  • HIV → Kaposi’s sarcoma
  • Helicobacter pylori → stomach cancer

4. Radiation

  • UV radiation → skin cancer
  • Ionizing radiation → leukemia and other cancers

5. Genetic Factors

Inherited mutations (e.g., BRCA genes) increase cancer risk.

Pathophysiology

1. Uncontrolled Cell Proliferation

Cancer cells ignore normal growth control signals and divide continuously. They may multiply slowly or rapidly depending on type.

2. Dedifferentiation

Cancer cells lose normal structure and function. Poorly differentiated tumors grow faster and behave more aggressively.

3. Invasiveness

Cancer cells invade nearby tissues by reducing cell adhesion and increasing mobility.

4. Metastasis

Spread from primary site to distant organs via:

  • Bloodstream
  • Lymphatic channels
  • Body cavities

Common metastatic sites include lungs, liver, bones and brain.

Genetic Basis of Cancer

  • Activation of proto-oncogenes → oncogenes (causing uncontrolled growth)
  • Inactivation of tumor suppressor genes (loss of growth regulation)

Symptoms of Cancer

Symptoms vary based on type and location but may include:

  • Unexplained weight loss
  • Fatigue
  • Skin changes (yellowing, darkening, redness)
  • Bowel or bladder changes
  • Persistent cough or hoarseness
  • Difficulty swallowing
  • Night sweats and fever
  • Pain due to nerve injury or tumor pressure
  • Bleeding disorders
  • Hormonal imbalances

Diagnosis of Cancer

  • Physical examination for lumps or abnormalities
  • Imaging: X-ray, CT, MRI, PET, ultrasound
  • Laboratory tests: CBC, tumor markers (CEA, AFP, HCG)
  • Biopsy: Gold standard for diagnosis
  • Genetic testing for inherited mutations
  • Autopsy in rare cases to confirm cause/development

Treatment of Cancer

  • Surgery: Removal of tumor
  • Chemotherapy: Drugs that kill cancer cells
  • Radiation therapy: High-energy beams to destroy cancer
  • Stem cell transplant: For blood cancers
  • Biological therapy: Cytokines, antibodies to enhance immunity
  • Hormone therapy: For hormone-dependent cancers
  • Gene therapy: Experimental approaches to repair defective genes
  • Targeted therapy: Drugs that block specific cancer cell pathways

Prevention

  • Avoid tobacco and alcohol
  • Healthy diet and weight control
  • Regular exercise
  • Vaccination (HBV, HPV)
  • Protection from sun exposure
  • Reduced exposure to carcinogens

Detailed Notes:

For PDF style full-color notes, open the complete study material below:

Share your love