Cancer



Cancer facts
• Second leading cause of death
• Classified by tissues or blood cells of origin
• Can metastasize by circulating through blood and lymphatic system, spreading to adjacent organs and tissues, and accidental transplantation during surgery
• No single cause identified.



Abnormal cell growth
Cancer is characterized by the abnormal growth of cells that develop from tissues or blood. Most cancers develop from epithelial tissues and are called carcinomas. Others arise from these tissues and cells:

• glandular tissues (adenocarcinoma)
• connective, muscle, and bone tissues (sarcomas)
• tissue of the brain and spinal cord (gliomas)
• pigmented cells (melanomas)
• plasma cells (myelomas)
• lymphatic tissue (lymphomas)
• luekocytes (leukemia)
• erythrocytes (erythroleukemia).


Uncontrolled cell growth
Cancer cells develop without the control that normal cell have and they spread from the site of origin in three ways:
• circulating through the blood and lymphatic system
• accidentally transplanted during surgery
• spreading to adjacent organs and tissues.


Causes of cancer
Carcinogenesis, the cell’s transformation from normal to cancerous, has no single cause but may result from complex interactions between:
• viruses
• physical and chemical carcinogens
• genetic, dietary, immunologic, and hormonal factors.


How cancer develops
Breast cancer — genetic link BRCA1 and BRCA2
Colorectal cancer — genetic link deletion on chromosomes 17 and 18 may promote malignancy.
Hodgkin’s disease — virus may have indirect relationship. Proliferation of
lymphocytes and histiocytes cause lymph node enlargement.
Acute leukemia — immature cells transform to leukemia cells, multiply, crowd out other cells.
Chronic myelogenous leukemia — Philadelphia chromosome present; in the terminal phase myeloblasts proliferate rapidly.
Chronic lymphocytic leukemia — proliferation and accumulation of immunodeficient lymphocytes.
Lung cancer — epithelial cells develop chromosomal changes, dysplastic cells arise, cells turn into cancer and invade deeper tissues.
Malignant melanoma — arises from melanocytes, spreads through lymph and vascular systems, metastasizes in skin, liver, lungs, CNS.
Multiple myeloma — B lymphocytes stimulated to turn into malignant plasma cells; leads to hyperviscosity.
Prostate cancer — age, diet high in saturated fats, and hormones play a role; cancer grows slowly.

No comments

Powered by Blogger.