than 70% of women who develop breast cancer have no known
risk factors for the disease.
Breast cancer is oFen signaled by a change in skin
texture, skin puckering, or leakage from the nipple. Since most
breast lumps are discovered by women themselves in routine
monthly breast exams, this simple examination should be a pri-
ority in every woman’s life.
Te American Cancer Society has recommended
—X-ray examination that detects breast cancers too small
to feel (less than 1 cm)—every year for women over 40 years old
(Figure 27.18)
. However, some authorities suggest that yearly
is too frequent, and the U.S. Prevention Services ±ask ²orce on
Breast Cancer Screening recommends delaying mammography
screening until age 50.
Diagnostic MRI scans seem to be preferable for at-risk
women who carry a mutated
gene. Besides heightened
monitoring, many women with the BRCA mutation are opt-
ing to have their breasts and/or ovaries surgically removed as a
preventive measure.
Once diagnosed, breast cancer is treated in various
ways depending on specific characteristics of the lesion. Current
therapies include (1) radiation therapy, (2) chemotherapy, and
(3) surgery, oFen followed by radiation or chemotherapy to de-
stroy stray cancer cells. Drug therapies for estrogen-responsive
cancers include:
of the breast is largely undeveloped and the duct system is rudi-
mentary. ²or this reason, breast size is largely due to the amount
of fat deposits.
Breast Cancer
Except for nonmelanoma skin cancer, invasive breast cancer
is the most common malignancy and the second most com-
mon cause of cancer death of U.S. women. Tirteen percent of
women in the general population (132 out of 1000 individuals)
will develop this condition—approximately 207,000 cases of in-
vasive breast cancer and an additional 54,000 cases of noninva-
sive breast cancer annually.
Breast cancer usually arises from the epithelial cells of the
smallest ducts, not from the alveoli. A small cluster of cancer
cells grows into a lump in the breast from which cells eventually
Known risk factors for developing breast cancer include:
early onset menstruation and late menopause, no pregnancies
or first pregnancy later in life and no or short periods of breast
feeding, and family history of breast cancer (especially in a sister
or mother).
Some 10% of breast cancers stem from hereditary defects
and half of these can be traced to dangerous mutations in a pair
of genes, dubbed
(breast cancer 1) and
. Of those
who carry the altered genes, 50–80% develop breast cancer, and
have a greater risk of ovarian cancer as well. However, more
Skin (cut)
Pectoralis major muscle
Suspensory ligament
Adipose tissue
Opening of lactiferous duct
Lactiferous sinus
Lactiferous duct
(superficial fascia)
Intercostal muscles
Lobule containing alveoli
First rib
Figure 27.17
Structure of lactating mammary glands. (a)
Anterior view of a partially
dissected breast.
Sagittal section of a breast.
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