Human Health and Diseases - Notes | Class 12 | Part 4: Cancer



·   Cancer is an abnormal and uncontrolled multiplication of cells resulting in the formation of tumour (masses of cells).

·   Normal cells show a contact inhibition (contact with the other cells inhibits their uncontrolled growth). Cancer cells do not have this property.

Types of Tumours

o Benign tumours: Confined to the place of its origin. They do not spread to other parts. Cause little damage.

o Malignant tumours: Mass of proliferating cells (neoplastic or tumour cells) that grow rapidly, invade and damage the surrounding normal tissues. Due to active division and growth, they starve normal cells by competing for nutrients.

Cells sloughed from tumours reach other sites via blood where they form a new tumour. This is called metastasis.

Causes of cancer (Carcinogens)

§ Physical agents: E.g. Ionizing radiations like X-rays and gamma rays and non-ionizing radiations like UV.

§ Chemical agents: Tobacco smoke (major cause of lung cancer), vinyl chloride, caffeine, nicotine, mustard gas etc.

§ Biological agents: E.g. oncogenic viruses, c-onc (cellular oncogenes or proto oncogenes) etc. When C-onc in normal cells is activated, the cells become oncogenic.

Cancer detection and diagnosis

o Biopsy: A thin piece of the suspected tissue is stained and examined under microscope (histopathological studies).

   In case of leukemia: Biopsy & histopathological studies. Blood & bone marrow tests for increased cell counts.

o Imaging techniques:

§ Radiography: Use of X-rays.

§ CT (Computerized tomography) scan: Uses X-rays to generate a 3D image of the internals of an object.

§ MRI (Magnetic Resonance Imaging): Uses magnetic fields and non-ionising radiations to detect pathological and physiological changes in the living tissue.

o Use of Antibodies against cancer-specific antigens.

o Molecular biology technique:  To detect cancer related genes. Such individuals should avoid carcinogens (e.g. tobacco smoke).

Treatment of cancer

o Radiotherapy: Tumour cells are irradiated lethally, without damaging surrounding normal tissues.

o Chemotherapy: Use of chemotherapeutic drugs. Many drugs have side effects like hair loss, anaemia etc.

o Immunotherapy: The patients are given biological response modifiers (e.g. α- interferon) which activates their immune system and helps in destroying the tumour.

o Surgery.

Most cancers are treated by combination of surgery, radiotherapy and chemotherapy.


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