Normal breast cells grow and divide in a controlled manner to replace cells that have died because of damage or age. Breast cancer is a disease in which abnormal breast cells increase in size, divide and destroy normal tissue.
As the cancer cells grow out of control for several months or years, they can form different types of cancerous tumours. One is called an in situ carcinoma (cancer), which means the cancer cells are growing inside a boundary that separates the tumour from surrounding tissues. This boundary is like a capsule that contains the tumour.
The cells may acquire the ability to become invasive, which is another form of tumour in which some cells break through the boundary and invade nearby tissues.
This type of cancer is life-threatening if the cells reach vital organs like the kidneys, lungs, or liver. The danger is even greater if the cells become malignant, and the invasive tumour cells gain the ability to enter the blood stream or lymphatic system and travel to distant areas in the body to form new tumours, which is called metastatic cancer.
The symptoms of breast cancer
Breast cancer is most often noticed first as a painless lump in the breast or armpit. You or your partner may discover the lump, or your doctor may find it during a routine physical exam or screening mammogram.
Other signs might include:
- Lump or swelling in the armpit
- Changes in breast size or shape
- Dimpling or puckering of the skin–thickening and dimpling skin is sometimes called “orange peel”
- Redness, swelling and increased warmth in the affected breast (these may be symptoms of inflammatory breast cancer)
- Inverted nipple (nipple turns inwards)
- Crusting or scaling on the nipple
These symptoms can also be caused by health problems other than cancer.
Testing is necessary to make a diagnosis. Remember, most lumps that are not breast cancer–lumps in the breast are very common, especially just before your period.
What increases your risk of breast cancer?
Most cases of breast cancer — a full 80% — happen in women who are over the age of 50.
Some risk factors for breast cancer include:
- Having had breast cancer before
- Family history of breast cancer (especially in a mother, sister or daughter diagnosed before menopause or if mutations on BRCA1 or BRCA2 genes are present)
- Family history of ovarian cancer
- An above-average exposure to the hormone estrogen, which your body produces naturally, perhaps because you:
- Have never given birth or gave birth for the first time after age 30
- Began menstruating at a young age
- Reached menopause later than average
- Have taken hormone replacement therapy (estrogen plus progestin) for more than five years
- Have dense breast tissue (as shown on a mammogram)
- Have a history of breast biopsies showing certain breast changes, such as an increased number of abnormal cells that are not cancerous (atypical hyperplasia)
- Had radiation treatment to the chest area (for example, to treat Hodgkin’s lymphoma), especially before age 30
Other factors slightly increase your risk of breast cancer. You may be at slightly higher risk if you:
- Are obese (especially after menopause)
- Drink alcohol
- Take birth control pills for four or more years before your first full term pregnancy
Some women develop breast cancer without having any of these risk factors. Most women with breast cancer do not have a family history of the disease.
Learn more about how to prevent breast cancer by reading Lifestyle factors and the risk of breast cancer. Want more information and support? Search "breast cancer" in Find Support. for organizations in your area.