Which Breast Typically Gets Cancer?

Breast cancer refers to the uncontrollable growth of cells that starts in the breast tissue. Cancer cells divide rapidly and lose their functionality. 

Breast cancer usually develops within the lobules where breast milk is produced or ducts that carry milk to the nipples of the breast. Cancer may develop within the connective tissue and fatty tissues.

Cancer that develops in the breast may spread to the surrounding tissue and throughout the body and cause cancer in other parts of the body. This condition is known as metastasis.

Being a woman and age older than 50 years is the most important risk factor for breast cancer.

Risk factors that cannot be changed include:

• Genetics: Breast cancer is estimated to be hereditary in 5 to 10 percent of cases, originating directly from gene defects (caused by mutations) passed on through generations.
• Period of menstruation: Women who had their menstrual cycles started at an early age such as before 12 years or who had attained menopause after 55 years were at risk of breast cancer because they had prolonged exposure to hormones estrogen and progesterone.
• History of cancer: Women who had a history of other cancer and who underwent radiation therapy of the chest during teenage or young adulthood are at a greatly elevated risk of breast cancer.
• Family history: Women who have close blood relations who have breast cancer are at high risk. A woman's risk of breast cancer is almost doubled if she has one first-degree family (mother, sister, or daughter) who has the disease. Having two first-degree relatives may triple her risk of breast cancer. Having a father or brother with breast cancer can increase the risk.
• Ethnicity: Caucasian women are more likely to develop breast cancer than African American women, but African American women have a higher risk of dying from cancer. Asian, Hispanic, and Native American women are less likely to acquire and die from breast cancer.
• Exposure to diethylstilbestrol (DES): Pregnant women from the 1940s to 1960s were given the drug DES to prevent miscarriage. Later, it was found that moms who used DES during pregnancy may be at a slightly high risk of breast cancer.

Risk factors that can be eliminated with lifestyle modifications include:

• Having children: Pregnancy reduces the risk of breast cancer because the overall number of menstrual cycles reduces with pregnancy. Having multiple pregnancies and pregnancy at a young age reduces the risk of breast cancer. However, never having children or having a first child after 30 years of age may increase the risk of breast cancer.
• Breastfeeding: Studies report that continuous breastfeeding for 1.5 to 2 years may reduce the risk of breast cancer.
• Hormone replacement therapy: Women who receive hormone replacement therapy, especially with combination therapy of both hormones estrogen and progesterone, may have an increased risk of breast cancer while being on therapy. However, with the discontinuation of combination therapy, the risk reduces.
• Oral contraceptives: Research suggests that women who take oral contraceptives (birth control pills) have a slightly high risk of breast cancer. The risk reduces after stopping the pills.
• Alcohol use: Consumption of excess alcohol may increase the risk of breast cancer.
• Physical activity: Indulging in physical activity was proved to be effective in reducing the risk of breast cancer.

Depending on the type of cells that becomes cancerous, breast cancer is classified into various types, which include:

1. Ductal carcinoma: Ductal carcinoma is the most common type of breast cancer that is developed from the epithelial cells in the milk ducts that carry milk from the breast to the nipples, which is of two types:
   • Ductal carcinoma in situ: A precancerous condition that does not spread to surrounding breast tissue
   • Invasive ductal carcinoma: Cancer spreads to surrounding tissues accounting for 70 to 80 percent of all types of breast cancer
2. Lobular carcinoma: It is cancer developed from epithelial cells that line the lobules of the breast that produce breast milk and is of two types:
   • Lobular carcinoma in situ: A precancerous condition that is quite uncommon
   • Invasive lobular carcinoma: Begins in the lobules and spreads to the surrounding tissues
3. Inflammatory breast cancer: This is a rare type of cancer that accounts for one to five percent of all types of breast cancer, but it is a very aggressive type of breast cancer. Cancer cells block the blood vessels and lymph nodes that make the breasts look swollen, red, and tender. Eventually, the breasts become heavier, thickened, and feel warm.
4. Triple-negative breast cancer: Unlike other breast cancer cells, these cancer cells do not have estrogen or progesterone receptors and produce little or no human epidermal growth factor receptor 2. Due to the lack of hormonal receptors, treating this type of cancer cells with hormone therapy is not possible, but treatment with chemo drugs may be effective. This is a very aggressive type of breast cancer that accounts for 15 percent of all types of breast cancer.
5. Angiosarcoma: Angiosarcoma of the breast develops within the lining of the blood vessels and lymph vessels in the breast and involves surrounding the breast tissue and skin. This is the rarest type of breast cancer that accounts only for one percent of all types of breast cancer. It may be caused by prior radiation therapy done to that area.
6. Paget’s disease of the breast: Paget’s disease of the breast is uncommon and accounts for only about one to three percent of all types of breast cancer. It begins in the breast ducts and spreads to the nipple skin and subsequently to the areola (the dark circle around the nipple).
7. Phyllodes tumor: Phyllodes tumors are a type of uncommon breast tumor. In contrast to carcinomas, which originate in the ducts or lobules, Phyllodes tumors develop in the connective tissue (stroma) of the breast. The majority are benign (noncancerous); however, there are a few that are cancerous.

Not all patients with breast cancer need to have symptoms, and if present, they may vary from one patient to another.

Common symptoms of breast cancer include:

1. Presence of a lump in the breast or the armpit
2. Breast pain at any location
3. Swelling that is felt in some part of the breast
4. Soreness around the nipple or pulling of the nipple
5. Dimpling or irritation of the breast skin
6. Discharge of fluids other than breast milk or blood from the nipple
7. Red of flaky skin around the nipple 
8. Changes in the size and shape of the breast

Breast cancer is differentiated into five stages (0 to IV) depending on the following:

• Size of the tumor
• Type of tumor whether it is invasive or noninvasive
• Involvement of the lymph nodes
• Metastasis

The five stages of breast cancer include:

1. Stage 0: Breast cancer is said to be in stage 0 when the cancer cells are present only in the milk ducts of the breast, and this is known as ductal carcinoma in situ. 
2. Stage I:
   • Stage Ia: The size of the tumor is two centimeters; cancer cells invade other parts of the breast, but cancer does not spread to lymph nodes and other parts of the body.
   • Stage Ib:
     • The tumor is absent in the breast, but small groups of cancer cells are present in the lymph nodes that are no larger than two millimeters.
     • The size of the tumor is smaller than two centimeters, and cancer cells found in the lymph nodes are not larger than two millimeters.
3. Stage II:
   • Stage IIa:
     • The tumor is absent in the breast, but small cancer cells larger than two millimeters are seen in one to three axillary lymph nodes (lymph nodes in the arm) or lymph nodes under the breastbone.
     • The size of the tumor is two centimeters, and cancer cells are seen in axillary lymph nodes.
     • The size of the tumor ranges between two and five centimeters without any involvement of the lymph nodes.
   • Stage IIb:
     • The size of the tumor ranges between two and five centimeters, and small cancer cells not larger than two millimeters are present in the lymph nodes.
     • The size of the tumor ranges between two and five centimeters, and cancer spreads to one to three axillary lymph nodes (lymph nodes in the arm) or lymph nodes under the breastbone.
     • The size of the tumor is larger than five centimeters, but the axillary lymph nodes are not involved.
4. Stage III:
   • Stage IIIa:
     • The breast may have no tumor at all, or a tumor of any size may be present; the main feature of this stage is the presence of cancer in four to nine axillary lymph nodes or lymph nodes under the breastbone.
     • The size of the tumor is larger than five centimeters; cancer cells not larger than two millimeters are present in the lymph nodes, or one to three axillary lymph nodes or lymph nodes under the breastbone are involved.
   • Stage IIIb:
     • The tumor may be of any size, but it invades the chest wall or skin.
     • Cancer cells may be seen in up to nine axillary lymph nodes or lymph nodes under the breastbone.
   • Stage IIIc:
     • The tumor may be absent in the breast, or the tumor may be of any size that invades the chest wall or skin and cancer is found.
       • 10 or more axillary lymph nodes
       • Lymph nodes above or below the collarbone
       • Lymph nodes near the breastbone
       • Internal mammary nodes
5. Stage IV: The tumor may be of any size, but cancer spreads to the lymph nodes around the breast, distant lymph nodes, and other organs of the body such as
   • Lungs
   • Skin
   • Brain
   • Liver
   • Bones

The following tests detect the presence of lumps in the breast and differentiate between benign and malignant tumors.

1. Mammogram: Mammogram, also referred to as mammography, is a radiological imaging technique that uses X-rays to examine the breasts. The breasts are exposed to a low dose of ionizing radiation, and images of the insides of the breasts are captured. These images show us any possible tumors in the breasts.
2. Breast ultrasound: Ultrasound waves are used to detect the presence of lumps in the breasts. This is helpful to detect lumps that are not visible in a mammogram. A breast ultrasound helps determine if the lump is a solid or a cyst.
3. Ultrasound-guided biopsy: A needle is inserted into the lump while using real-time ultrasound images to aspirate some tissue. This tissue is analyzed under the microscope to determine the presence of cancer cells.
4. Magnetic resonance imaging (MRI) of the breasts: MRI is another imaging technique performed to visualize the insides of the breast. MRI helps analyze breast tumors that are not detectable on mammography or ultrasound, especially in women with thick breast tissue.
5. MRI-guided biopsy: MRI-guided biopsy is performed to aspirate abnormal breast tissue through a needle for microscopic analysis.
6. Positron emission tomography/Computed tomography (PET/CT): With the help of a combined imaging technique of PET/CT, doctors can see sites of abnormal metabolic activity within the breasts. PET/CT not only identifies breast cancer but also determines the spread of cancer to other parts (metastasis), evaluates the effectiveness of the treatment, and determines relapse of the disease following treatment.

The treatment regimen for breast cancer may vary from patient to patient because it depends on both the type and stage of cancer.

Usually, a patient may receive different treatments where one type treats cancer and the other one may help prevent reoccurrence.

1. Surgery: Surgeries such as lumpectomy (breast-conserving surgery) and mastectomy (removal of the breast) may be performed depending on the condition of the patient and stage and grade of the tumor. Along with breast tissue removal, local lymph nodes will be removed. The doctor may perform a breast reconstruction surgery after a few months or years following a mastectomy.
2. Chemotherapy: Special drugs are injected into the patient’s body or given to them orally in consecutive cycles. These drugs attack cancer cells and kill them. They attack normal functioning cells in the body, leading to various side effects. However, the advantage of chemo drugs is greater than the side effects because they improve the life span of the patient and reduce symptoms of cancer. Chemotherapy may be given as a primary treatment or given before or after surgery to eliminate cancer cells.
3. Radiation therapy: Radiation therapy is given to a patient following a lumpectomy or mastectomy or given adjuvant with chemotherapy to kill cancer cells with high energy particles such as
   • X-rays
   • Gamma rays
   • Protons
   • Electron beams
4. Hormonal therapy: Breast cancer cells grow under the influence of the estrogen hormone. Hormone therapy is given to patients to prevent the effect of estrogen on breast cancer cells. This prevents the growth of cancer cells.
5. Targeted therapy: Targeted therapy drugs directly act on proteins of the cancer cells that are responsible for their growth and destroy them or slow down their growth.
6. Immunotherapy: Immunotherapy drugs boost immune cells in the body such that they recognize and eliminate the cancer cells from the body.