Encyclopedia of Health and Medicine

CANCER
The area of health care concerned with cancer prevention and treatment is oncology. Doctors who specialize in cancer
treatment are oncologists. This section, “Cancer,” presents an overview discussion of current understanding about cancer
and entries about cancer concepts and treatments. Entries in other sections of The Facts On File Encyclopedia of
Health and Medicine provide detailed content about specific types of cancer.
For example, this section, “Cancer,” contains the
entry HORMONE-DRIVEN CANCERS, whereas while the
section “The Reproductive System” contains
entries for BREAST CANCER, PROSTATE CANCER, and
TESTICULAR CANCER. Cross-references connect
entries with one another.
Cancer: Uncontrolled Cell Proliferation
Cancer is the uncontrolled growth and division
(proliferation) of cells. Cancer cells lack the proper
mechanisms for APOPTOSIS, the natural process that
establishes the end of a cell’s life cycle. In this
regard, cancer cells have an endless open throttle:
they can divide forever. Cancer cells also lack the
proper mechanisms for self-regulation that shut
down cell division in abnormal cells; they never
stop growing and dividing.
Ordinarily the IMMUNE SYSTEM detects cells that
present a threat to the body and mobilizes an
IMMUNE RESPONSE to neutralize them before they
can do much damage. Cancer cells appear able to
evade such detection by the immune system
because they arise from cells that belong to the
body (self cells). Even as they mutate cancer cells
retain enough essence of their self-cell origin to
fool the immune system into continuing to perceive
them as self cells. This deception allows cancer
cells to congregate, forming the tumors that
characterize the disease process of cancer.
Cancer may develop in any cell, with the potential
to affect any kind of body tissue. The cells form
tumors that invade healthy tissues and can spread
to parts of the body beyond the site of origin.
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Cancer is a threat to health because its presence
within tissues and organs disrupts their structure
and functions. Cancer tumors take space, NUTRI-
ENTS, and structure that tissues and organs need.
Heredity, Environment, and Aging
Researchers believe cancer is the result of genetic
damage within individual cells that allows uncontrolled
cell division and growth. This damage may
occur as a consequence of heredity or environment
or may develop through the process of
aging.
Heredity and cancer The tendency toward cancer
appears to run in families, providing much
anecdotal evidence of genetic mutations that contribute
to the risk for cancer. Researchers also
have isolated specific genes for certain types of
cancer, providing objective evidence that cancer
can have a hereditary component. When this is
the case, a person inherits mutated genes that do
not properly regulate specific functions. This lack
of regulation results in abnormal cell growth and
division that can result in cancer. The BRCA-
1/BRCA-2 GENE mutations are among the best
known; these mutations are prominent in women
who have some types of OVARIAN CANCER or breast
cancer. However, only a small percentage of
women who have these gene mutations develop
cancer, evidence that many factors converge
when cancer occurs.
Environmental influences and cancer More
than a thousand substances found in the environment,
natural and synthetic, may cause cancer.