What is breast cancer?
Breast cancer is a malignant tumor that develops in the breast tissue and rapidly invades the surrounding tissue. It is the most common form of malignancy in women in Western countries, with the exception of skin cancers. Apart from other risk factors, identification of breast cancer genes BRCA 1 and BRCA 2 strongly suggests that certain women have a genetic predisposition to developing this disease. Outlook is good if the cancer is detected early and appropriate treatment instituted. With increased awareness about breast cancer in this day and age, coupled with advances in diagnosis and treatment has definitely improved the outlook. Although breast cancer is predominantly a woman’s disease, it may rarely develop in men.
The breast is composed of 15 to 20 lobes. Each lobe is made up of lobules which are the milk producing glands. During breastfeeding, the lactiferous or milk ducts carry milk from the glands to the nipples. Fatty tissue, glands, and connective tissue make up most of the breast tissue. For more information, refer to female breast anatomy.
Cancer is a type of abnormal growth where cells multiply profusely, are abnormal in structure and invade surrounding tissue. It can arise from any tissue that makes up the breast but more commonly arises from the glandular epithelium lining the ducts. The transition from normal to cancerous cells may lead to a number of abnormalities in cell stucture and growth pattern that is neither normal, nor cancer. This is explained further under different types of breast tumors.
Types of Breast Cancer
- Carcinoma in situ is a pre-invasive cancer which has not breached the epithelial basement membrane. Most cases are asymptomatic and are usually detected during routine mammography.
- The hormone estrogen may cause some breast cancers to grow. These cancers, which have estrogen receptors on the surface of their cells, are said to be estrogen sensitive or estrogen dependent. Such cancers are known as estrogen receptor-positive or ER-positive breast cancers.
- HER 2 (human epidermal growth factor receptor 2) is a gene that is responsible for cell growth, cell division, and cell repair. Certain cancer cells have excess copies of this gene, which not only makes the cancer grow aggressively but it also has a tendency to recur. This type of breast cancer is known as HER 2-positive breast cancer.
- Ductal carcinoma. Cancer can arise from any of the tissues making up the breast, but it most frequently does so from the glandular epithelium lining the lactiferous ducts. This makes up about 80% of breast cancers. It may be in situ, when it is known as ductal carcinoma in situ (DCIS) or intraductal carcinoma. Routine mammography may be able to identify DCIS. Ductal carcinoma that spreads to surrounding tissues is known as invasive or infiltrating ductal carcinoma.
- Lobular carcinoma is a type of cancer develops in the lobules of the breast. It occurs in about 10 to 15% of cases. This may alsobe in situ (lobular carcinoma in situ or LCIS) or invasive (infiltrating lobular carcinoma).
- Rare histological types of breast cancer, which often have a better prognosis, includes :
- colloid carcinoma
- medullary carcinoma
- tubular carcinoma
- Inflammatory carcinoma is a rare but highly aggressive type of breast cancer, occurring due to blockage of the lymph vessels under the skin by cancer cells. On examination, the breast appears red, warm, swollen, and painful.
Risk Factors of Breast Cancer
- Age. Breast cancer may develop any time after the age of 20, but rarely before that. Risk increases with age.
- Geography. Breast cancer is more common in Western countries.
- Gender. Only 1% of breast cancer patients are male.
- Family history of breast cancer in first degree relatives (mother, sister, or daughter) increases the risk.
- Genetic factors. Inherited genetic mutations (alteration in the body’s genetic material) may be responsible for breast cancer. In about 5% of cases, mutations in the breast cancer genes BRCA 1 and BRCA 2 can be identified which may be a predisposing factor. A blood test may be done to test for alterations in a person’s BRCA 1 or BRCA 2 genes if there is a family history of breast cancer. If a woman tests positive for BRCA mutations, she may go for the most drastic option, that of prophylactic mastectomy (removal of the breasts). The other options available to decrease the risk of breast cancer are frequent cancer screenings, avoiding other risk factors, and prophylactic drug therapy such as tamoxifen and raloxifene.
- Past history of breast cancer.
- Personal history of ovarian, endometrial, or colon cancer.
- High fat diet.
- Alcohol intake.
- Nulliparity – never having been pregnant.
- Late age at first birth (having the first child later in life).
- Early menarche (onset of menstruation) before the age of 12 and late menopause after the age of 45. This may be related to more menstrual cycles in life which is associated with a higher incidence of breast cancer.
- Hormone replacement therapy (HRT).
- Contraceptive pills.
- Diethylstilbestrol (DES) is a drug which was previously given for the prevention of miscarriage but its use has now been discontinued in pregnant women. Women who had taken this drug may be at increased risk of breast cancer.
- Previous radiation therapy.
Early age at first birth and breastfeeding seem to protect against breast cancer.
Spread of Breast Cancer
Breast cancer may spread by the following means :
- Local spread. As the tumor increases in size, it may eventually involve the surrounding tissue and spread to the skin, pectoral muscles, and chest wall.
- Lymphatic spread. Cancer cell may spread to the axillary lymph nodes in the armpit and the internal mammary chain of lymph nodes. In late stages of the disease, the supraclavicular nodes and lymph nodes of the opposite side of the body may be involved.
- Bloodstream. Metastasis may occur in the liver, lungs, brain, and bones. The bones most commonly affected are lumbar and thoracic vertebrae, femur, ribs, and skull.
Signs and Symptoms of Breast Cancer
Early breast cancer may not cause any symptoms and may only be detected by screening mammography. The common signs and symptoms are :
- Firm breast lump, most often present in the upper and outer quadrant of the breast, and in the region behind the nipple and areola. The tumor is usually painless. The margin may be irregular and the tumor may be fixed to the underlying tissue.
- Breast pain may be present but is rare.
- Nipple retraction of recent onset.
- Dimpling of the skin (peau d’ orange).
- Nipple discharge, which may be blood stained.
- Symptoms of metastasis (distant spread to other sites), such as bone pain and shortness of breath.