Webster's New World Medical Dictionary

branchial cleft cyst
A cavity that is a remnant
from embryologic development and is still present
at birth in one side of the neck, just in front of the
large angulated muscle on either side (the stern-
ocleidomastoid muscle). The cyst may not be rec-
ognized until adolescence, when it enlarges its oval
shape. Sometimes a branchial cleft cyst develops a
sinus or drainage pathway to the surface of the skin,
from which mucus can be expressed. Total surgical
excision is the treatment of choice. Also known as
branchial cyst.
branchial cyst
See 
branchial cleft cyst.
Braxton Hicks contraction
An irregular con-
traction of the womb (uterus) that occurs toward
the middle of a woman’s first pregnancy and earlier,
and more intensely, in her subsequent pregnancies.
Braxton Hicks contractions tend to occur during
physical activity. The uterus tightens for 30 to 60
seconds, beginning at the top of the uterus, and the
contraction gradually spreads downward before the
uterus relaxes. Braxton Hicks contractions may be
quite uncomfortable and sometimes difficult to dis-
tinguish from the contractions of true labor.
BRCA1
A tumor suppressor gene that normally
acts to restrain the growth of cells. Mutated forms of
BRCA1 and BRCA2 are responsible for about half
the cases of inherited breast cancer, especially those
that occur in relatively young women. From the
words breast and cancer. See also 
breast cancer
susceptibility gene.
BRCA2
A tumor suppressor gene that normally
acts to restrain the growth of cells. Mutations of
BRCA2, like those of BRCA1, are responsible mainly
for hereditary breast cancer. They seldom appear to
be involved in sporadic, noninherited breast can-
cer—the 95 percent of breast cancer that does not
run in families. Both BRCA1 and BRCA2 are large,
complex genes. From the words breast and cancer.
See also 
breast cancer susceptibility gene.