Webster's New World Medical Dictionary

breast cancer, familial
A form of breast cancer
that tends to occur in members of the same family. A
number of factors have been identified as increasing
the risk of breast cancer. One of the strongest is a
family history of breast cancer in a relative. About 15
to 20 percent of women with breast cancer have
such a family history of the disease, clearly reflecting
the participation of inherited (genetic) components
in the development of some breast cancers.
Dominant breast cancer susceptibility genes, includ-
ing BRCA1 and BRCA2, appear to be responsible for
about 5 percent of all breast cancer. See also 
BRCA1;
BRCA2; breast cancer susceptibility gene.
breast cancer, male
Breast cancer in men. Male
breast cancer is much less common than breast
cancer in women. Fewer than 1 percent of persons
with breast cancer are male. However, breast can-
cer is no less dangerous in males than in females.
After the diagnosis of breast cancer is made, the
mortality rates are virtually the same for men and
for women.
breast cancer susceptibility gene
An inherited
factor that predisposes an individual to breast can-
cer. Two of these genes, BRCA1 and BRCA2, have
been identified. Several other genes (those for Li-
Fraumeni syndrome, Cowden disease, Muir-Torre
syndrome, and ataxia-telangiectasia) are also
known to predispose women to breast cancer.
However, because all these known breast cancer
susceptibility genes together do not account for
more than a minor fraction of breast cancer that
clusters in families, it is clear that more breast can-
cer genes remain to be discovered. See also 
BRCA1;
BRCA2.
breast implant
See 
breast augmentation.
breast milk
Milk from the breast. Human milk
contains a balance of nutrients that closely matches
infant requirements for brain development, growth,
and a healthy immune system. Human milk also
contains immunologic agents and other compounds
that act against viruses, bacteria, and parasites.