About Breast Cancer
Breast cancer develops in the breast tissue, primarily in the milk ducts (ductal carcinoma) or glands (lobular carcinoma). The cancer is still called and treated as breast cancer even if it is first discovered after traveling to other areas of the body such as the lungs, liver, or bones. In those cases, the cancer is referred to as metastatic or advanced breast cancer.
Breast cancer usually begins with the formation of a small, confined tumour (lump), or as calcium deposits (micro calcifications) and then spreads through channels to the lymph nodes or through the blood stream to other organs. The tumour may also grow and invade tissue around the breast, such as the skin or chest wall. Different types of breast cancer grow and spread at different rates -- some take years to spread beyond the breast while other move quickly.
Some lumps are benign (not cancerous), however these can be premalignant. The only safe way to distinguish between a benign lump and cancer is to examine the tissue after a biopsy. Men can get breast cancer, too, but they account for less than 0.5% of all cases. Among women, breast cancer is the most common cancer and the second leading cause of cancer deaths behind lung cancer.
Fortunately, breast cancer is very treatable if detected early. Localized tumours can usually be treated successfully before the cancer spreads; and in nine in 10 cases, the woman will live at least another five years. Experts usually consider a five-year survival to be a cure although recurrences after five years are common.
Causes of Breast Cancer
Although the precise causes of breast cancer are unclear, the main risk factors are known. Among the most significant factors are
- advancing age and
- A family history of breast cancer.
Risk increases slightly for a woman who has had a benign breast lump and increases significantly for a woman who has previously had breast cancer or a history of endometrial, ovarian, or colon cancer. A woman whose mother, sister, or daughter has had breast cancer is two to three times more likely to develop the disease, particularly if more than one first-degree relative has been affected. This is especially true if the cancer developed in the woman while she was premenopausal, or if the cancer developed in both breasts.
Researchers have now identified two genes responsible for some instances of familial breast cancer -- called BRCA1 and BRCA2. About one woman in 200 carries it. Having the gene predisposes a woman to breast cancer and -- while it does not ensure that she will get breast cancer -- her lifetime risk is 56%-85%. Because of this, risk prevention strategies and screening guidelines for those with the BRCA genes are more aggressive. There are other genes that have been identified as increasing the risk of breast cancer, including the PTEN gene, the ATM gene, and the CHEK2 gene. However, these genes carry a lower risk for breast cancer development than the BRCA genes.
Generally, women over 50 are more likely to get breast cancer than younger women, and African-American women are more likely than Caucasians to get breast cancer before menopause.
A link between breast cancer and hormones is gradually becoming clearer. Researchers think that the greater a woman's exposure to the hormone oestrogen, the more susceptible she is to breast cancer. Oestrogen tells cells to divide; the more the cells divide, the more likely they are to be abnormal in some way, possibly becoming cancerous.
The link between diet and breast cancer is debated. Obesity is a noteworthy risk factor, predominately in postmenopausal women, because obesity alters a woman's oestrogen levels. Drinking alcohol regularly -- more than two drinks a day -- may also promote the disease. Many studies have shown that women, whose diets are high in fat, either from red meat or high-fat dairy products, are more likely to get the disease. Researchers suspect that if a woman lowers her daily calories from fat -- to less than 20%-30% -- her diet may help protect her from developing breast cancer.
Stages of Breast Cancer
- Early stage or stage
0 breast cancer
- The disease is localized to the breast with no evidence of spread to the lymph nodes (carcinoma in situ).
- Stage 1 breast cancer
- The cancer is two centimetres or less in size and it hasn't spread anywhere.
- Stage 2A breast cancer
- Tumour smaller than two centimetres across with lymph node involvement or a tumour that is larger than two but less than five centimetres across without underarm lymph node involvement.
- Stage 2B breast cancer
- Tumour that is greater than five centimetres across without underarm lymph nodes testing positive for cancer or a tumour that is larger than two but less than five centimetres across with lymph node involvement.
- Advanced breast cancer (metastatic) results after cancer cells spread to the lymph nodes and to other parts of the body.
- Stage 3A breast cancer
- Locally advanced breast cancer: The tumour is larger than five centimetres and has spread to the lymph nodes under the arm, or a tumour that is any size with cancerous lymph nodes that adhere to one another or surrounding tissue.
- Stage 3B breast cancer
- Tumour of any size that has spread to the skin, chest wall, or internal mammary lymph nodes.
- Stage 3C breast cancer
- Tumour of any size that has spread more extensively and involves more lymph node invasion.
- Stage 4 breast cancer
- Tumour, regardless of size, that has spread to places far away from the breast, such as bones, lungs, liver, brain, or distant lymph nodes.