Cancer is a group of
diseases in which cells are aggressive (grow and divide without
respect to normal limits), invasive (invade and destroy adjacent
tissues), and sometimes metastatic (spread to other locations in
the body). These three malignant properties of cancers
differentiate them from benign tumors, which are self-limited in
their growth and do not invade or metastasize (although some
benign tumor types are capable of becoming malignant). Cancer
may affect people at all ages, even fetuses, but risk for the
more common varieties tends to increase with age. Cancer causes
about 13% of all deaths. According to the ACS, 7.6 million
people died from cancer in the world during 2007. Apart from
humans, forms of cancer may affect other animals and plants.
Nearly all cancers are caused by abnormalities in the genetic
material of the transformed cells. These abnormalities may be
due to the effects of carcinogens, such as tobacco smoke,
radiation, chemicals, or infectious agents. Other
cancer-promoting genetic abnormalities may be randomly acquired
through errors in DNA replication, or are inherited, and thus
present in all cells from birth. Complex interactions between
carcinogens and the host genome may explain why only some
develop cancer after exposure to a known carcinogen. New aspects
of the genetics of cancer pathogenesis, such as DNA methylation,
and microRNAs are increasingly being recognized as important
.
Genetic abnormalities found in cancer typically affect two
general classes of genes. Cancer-promoting oncogenes are often
activated in cancer cells, giving those cells new properties,
such as hyperactive growth and division, protection against
programmed cell death, loss of respect for normal tissue
boundaries, and the ability to become established in diverse
tissue environments. Tumor suppressor genes are often
inactivated in cancer cells, resulting in the loss of normal
functions in those cells, such as accurate DNA replication,
control over the cell cycle, orientation and adhesion within
tissues, and interaction with protective cells of the immune
system.
Cancer is usually classified according to the tissue from which
the cancerous cells originate, as well as the normal cell type
they most resemble. These are location and histology,
respectively. A definitive diagnosis usually requires the
histologic examination of a tissue biopsy specimen by a
pathologist, although the initial indication of malignancy can
be symptoms or radiographic imaging abnormalities. Most cancers
can be treated and some cured, depending on the specific type,
location, and stage. Once diagnosed, cancer is usually treated
with a combination of surgery, chemotherapy and radiotherapy. As
research develops, treatments are becoming more specific for
different varieties of cancer. There has been significant
progress in the development of targeted therapy drugs that act
specifically on detectable molecular abnormalities in certain
tumors, and which minimize damage to normal cells. The prognosis
of cancer patients is most influenced by the type of cancer, as
well as the stage, or extent of the disease. In addition,
histologic grading and the presence of specific molecular
markers can also be useful in establishing prognosis, as well as
in determining individual treatments.
Classification Nomenclature
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Cancer
Classification
1. Nomenclature
2. Adult cancers
3. Childhood cancers
Signs and symptoms
Diagnosis
1. Investigation
2. Biopsy
Treatment
1. Surgery
2. Radiation therapy
3. Chemotherapy
4. Targeted therapies
5. Immunotherapy
6. Hormonal therapy
7. Symptom control
8. Complementary and alternative
9. Treatment trials
Prognosis
1. Emotional impact
Causes
1. Chemical carcinogens
2. Ionizing radiation &
Infectious diseases
3. Hormonal imbalances
& Immune system dysfunction
4. Heredity & Other causes
Pathophysiology
1. Epigenetics
2. Oncogenes
3. Tumor suppressor genes
4. Cancer cell biology
4.1 Clonal evolution
4.2 Biological properties of cancer cells
Prevention
1. Modifiable ("lifestyle") risk factors
2. Diet
3. Vitamins
4. Chemoprevention
5. Genetic testing
6. Vaccination
7. Screening
Epidemiology
History
Research |
