BREAST CANCER
Breast cancer is one of the most common cancers that affects women and people assigned
female at birth (AFAB). It happens when cancerous cells in your breasts multiply and become tumors.
About 80% of breast cancer cases are invasive, meaning a tumor may spread from your breast to
other areas of your body. Breast cancer typically affects women age 50 and older, but it can also
affect women and people AFAB who are younger than 50. Men and people assigned male at birth
(AMAB) may also develop breast cancer.
BREAST CANCER TYPES:
Invasive (infiltrating) ductal carcinoma (IDC): This cancer starts in your milk ducts and
spreads to nearby breast tissue. It’s the most common type of breast cancer in the United
States.
Lobular breast cancer: This breast cancer starts in the milk-producing glands (lobules) in
your breast and often spreads to nearby breast tissue. It’s the second most common breast
cancer in the United States.
Ductal carcinoma in situ (DCIS): Like IDC, this breast cancer starts in your milk ducts. The
difference is DCIS doesn’t spread beyond your milk ducts.
ANATOMY AND PHYSIOLOGY
Anatomy of the Breast
The breast is a glandular organ located on the anterior thoracic wall, composed of various
tissues, including glandular, adipose, and connective tissue.
Key Structures
1. Lobes and Lobules
o The breast consists of 15–20 lobes, each divided into smaller lobules, which produce
milk during lactation.
o Lobules contain alveoli lined with milk-secreting epithelial cells.
2. Ducts
o Ducts transport milk from the lobules to the nipple.
o Most breast cancers originate in the ductal cells (ductal carcinoma).
3. Stroma
o Includes adipose and connective tissue providing structural support.
o Cancer may invade this area as it progresses.
4. Nipple and Areola
o The nipple is the outlet for milk ducts, surrounded by pigmented areolar tissue.
5. Lymphatic System
o Includes axillary, internal mammary, and supraclavicular lymph nodes.
o Lymphatic vessels are common pathways for cancer metastasis.
6. Blood Supply
o Provided by the internal thoracic (mammary) artery, lateral thoracic artery, and
intercostal arteries.
o Blood vessels facilitate tumor angiogenesis and metastatic spread.
Physiology of the Breast
1. Hormonal Regulation
o The breast responds to hormones like estrogen, progesterone, and prolactin, which
regulate growth, development, and lactation.
o Estrogen promotes ductal growth, while progesterone stimulates lobular
development.
2. Growth and Development
o During puberty, hormonal surges stimulate breast tissue growth.
o During pregnancy, alveoli proliferate to prepare for milk production.
3. Lactation
o Prolactin triggers milk production, while oxytocin stimulates milk ejection through the
ducts.
Pathophysiological Changes in Breast Cancer
1. Abnormal Cellular Proliferation
o Mutations in epithelial cells disrupt the normal regulation of cell growth.
o Cancer often begins in ducts (ductal carcinoma) or lobules (lobular carcinoma).
2. Loss of Differentiation
o Cancer cells lose their specialized function and structural organization, appearing
abnormal under a microscope.
3. Disruption of the Basement Membrane
o Cancer cells invade surrounding stromal tissue, blood vessels, and lymphatics.
4. Hormonal Dysregulation
o Estrogen and progesterone receptor-positive cancers exploit hormonal signaling for
growth.
5. Lymphatic and Hematogenous Spread
o Cancer cells travel through the lymphatic system to lymph nodes or via blood vessels
to distant organs.
What causes breast cancer?
Experts know breast cancer happens when breast cells mutate and become cancerous cells
that divide and multiply to create tumors. They aren’t sure what triggers that change. However,
research shows there are several risk factors that may increase your chances of developing breast
cancer. These include:
Age: Being 55 or older.
Sex: Women and people AFAB are much more likely to develop the condition than men and
people AMAB.
Family history: If your parents, siblings, children or other close relatives have breast cancer,
you’re at risk of developing the disease.
Genetics: Up to 15% of people with breast cancer develop the disease because they have
inherited genetic mutations. The most common genetic mutations involve the BRCA1 and
BRCA2 genes.
Smoking: Tobacco use has been linked to many different types of cancer, including breast
cancer.
Drinking beverages containing alcohol: Research shows that drinking beverages
containing alcohol may increase breast cancer risk.
Having obesity.
Radiation exposure: If you’ve had prior radiation therapy — especially to your head, neck or
chest — you’re more likely to develop breast cancer.
Hormone replacement therapy: People who use hormone replacement therapy (HRT) have
a higher risk of being diagnosed with the condition.
What are breast cancer symptoms?
The condition can affect your breasts in different ways. Some breast cancer symptoms are very
distinctive. Others may simply seem like areas of your breast that look very different from any other
area. Breast cancer may not cause noticeable symptoms either. But when it does, symptoms may
include:
A change in the size, shape or contour of your breast.
A mass or lump, which may feel as small as a pea.
A lump or thickening in or near your breast or in your underarm that persists through your
menstrual cycle.
A change in the look or feel of your skin on your breast or nipple. Your skin may look dimpled,
puckered, scaly or inflamed. It may look red, purple or darker than other parts of your breast.
A marble-like hardened area under your skin.
A blood-stained or clear fluid discharge from your nipple.
