Facts on File Encyclopedia of Health and Medicine

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 SYSTEMdetects cells that
present a threat to the body and mobilizes an
IMMUNE RESPONSEto 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 per-
ceive them as self cells. This deception allows can-
cer cells to congregate, forming the tumors that
characterize the disease process of cancer.
Cancer may develop in any cell, with the poten-
tial 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.

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 uncon-

trolled cell division and growth. This damage may

occur as a consequence of heredity or environ-

ment or may develop through the process of

aging.

Heredity and cancerThe tendency toward can-

cer appears to run in families, providing much

anecdotal evidence of genetic mutations that con-

tribute 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 CANCERor 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 environ-

ment, natural and synthetic, may cause cancer.

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 can-
cer and entries about cancer concepts and treatments. Entries in other sections of The Facts On File Encyclopedia of
Health and Medicineprovide detailed content about specific types of cancer.

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