Breast cancer is the most common invasive cancer in women and the second leading cause of cancer death in women after lung cancer.
Breast cancer is cancer that develops in breast cells. Typically, the cancer forms in either the lobules or the ducts of the breast.
Lobules are the glands that produce milk, and ducts are the pathways that bring the milk from the glands to the nipple. Cancer can also occur in the fatty tissue or the fibrous connective tissue within your breast.
Breast cancer can spread outside the breast through blood vessels and lymph vessels. When breast cancer spreads to other parts of the body, it is said to have metastasized.
Kinds of Breast Cancer
The most common kinds of breast cancer are—
- Invasive ductal carcinoma. The cancer cells grow outside the ducts into other parts of the breast tissue. Invasive cancer cells can also spread, or metastasize, to other parts of the body.
- Invasive lobular carcinoma. Cancer cells spread from the lobules to the breast tissues that are close by. These invasive cancer cells can also spread to other parts of the body.
Types of Breast Cancer
- Ductal carcinoma in situ. Ductal carcinoma in situ (DCIS) is a noninvasive condition. With DCIS, the cancer cells are confined to the ducts in your breast and haven’t invaded the surrounding breast tissue.
- Lobular carcinoma in situ. Lobular carcinoma in situ (LCIS) is cancer that grows in the milk-producing glands of your breast. Like DCIS, the cancer cells haven’t invaded the surrounding tissue.
- Invasive ductal carcinoma. Invasive ductal carcinoma (IDC) is the most common type of breast cancer. This type of breast cancer begins in your breast’s milk ducts and then invades nearby tissue in the breast. Once the breast cancer has spread to the tissue outside your milk ducts, it can begin to spread to other nearby organs and tissue.
- Invasive lobular carcinoma. Invasive lobular carcinoma (ILC) first develops in your breast’s lobules and has invaded nearby tissue.
Other, less common types of breast cancer include:
- Paget disease of the nipple. This type of breast cancer begins in the ducts of the nipple, but as it grows, it begins to affect the skin and areola of the nipple.
- Phyllodes tumor. This very rare type of breast cancer grows in the connective tissue of the breast. Most of these tumors are benign, but some are cancerous.
- Angiosarcoma. This is cancer that grows on the blood vessels or lymph vessels in the breast.
The type of cancer you have determines your treatment options, as well as your likely long-term outcome.
Doctors know that breast cancer occurs when some breast cells begin to grow abnormally. These cells divide more rapidly than healthy cells do and continue to accumulate, forming a lump or mass. Cells may spread (metastasize) through your breast to your lymph nodes or to other parts of your body.
Breast cancer most often begins with cells in the milk-producing ducts (invasive ductal carcinoma). Breast cancer may also begin in the glandular tissue called lobules (invasive lobular carcinoma) or in other cells or tissue within the breast.
Researchers have identified hormonal, lifestyle and environmental factors that may increase your risk of breast cancer. But it’s not clear why some people who have no risk factors develop cancer, yet other people with risk factors never do. It’s likely that breast cancer is caused by a complex interaction of your genetic makeup and your environment.
Each type of breast cancer can cause a variety of symptoms. Many of these symptoms are similar, but some can be different. Symptoms for the most common breast cancers include:
- A breast lump or tissue thickening that feels different than surrounding tissue and has developed recently
- Breast pain
- Red, pitted skin over your entire breast
- Swelling in all or part of your breast
- A nipple discharge other than breast milk
- Bloody discharge from your nipple
- Peeling, scaling, or flaking of skin on your nipple or breast
- A sudden, unexplained change in the shape or size of your breast
- Inverted nipple
- Changes to the appearance of the skin on your breasts
- A lump or swelling under your arm
If you have any of these symptoms, it doesn’t necessarily mean you have breast cancer. For instance, pain in your breast or a breast lump can be caused by a benign cyst. Still, if you find a lump in your breast or have other symptoms, you should see your doctor for further examination and testing.
A doctor stages cancer according to the size of the tumor and whether it has spread to lymph nodes or other parts of the body.
There are different ways of staging breast cancer. One way is from stage 0–4, with subdivided categories at each numbered stage.
Descriptions of the four main stages are listed below, though the specific substage of cancer may also depend on other specific characteristics of the tumor, such as HER2 receptor status.
- Stage 0: Known as ductal carcinoma in situ (DCIS), the cells are limited to within the ducts and have not invaded surrounding tissues.
- Stage 1: At this stage, the tumor measures up to 2 centimeters (cm) across. It has not affected any lymph nodes, or there are small groups of cancer cells in the lymph nodes.
- Stage 2: The tumor is 2 cm across, and it has started to spread to nearby nodes, or is 2–5 cm across and has not spread to the lymph nodes.
- Stage 3: The tumor is up to 5 cm across, and it has spread to several lymph nodes or the tumor is larger than 5 cm and has spread to a few lymph nodes.
- Stage 4: Cancer has spread to distant organs, most often the bones, liver, brain, or lungs.
A breast cancer risk factor is anything that makes it more likely you’ll get breast cancer. But having one or even several breast cancer risk factors doesn’t necessarily mean you’ll develop breast cancer. Many women who develop breast cancer have no known risk factors other than simply being women.
Factors that are associated with an increased risk of breast cancer include:
- Being female. Women are much more likely than men are to develop breast cancer.
- Increasing age. Your risk of breast cancer increases as you age.
- A personal history of breast conditions. If you’ve had a breast biopsy that found lobular carcinoma in situ (LCIS) or atypical hyperplasia of the breast, you have an increased risk of breast cancer.
- A personal history of breast cancer. If you’ve had breast cancer in one breast, you have an increased risk of developing cancer in the other breast.
- A family history of breast cancer. If your mother, sister or daughter was diagnosed with breast cancer, particularly at a young age, your risk of breast cancer is increased. Still, the majority of people diagnosed with breast cancer have no family history of the disease.
- Inherited genes that increase cancer risk. Certain gene mutations that increase the risk of breast cancer can be passed from parents to children. The most well-known gene mutations are referred to as BRCA1 and BRCA2. These genes can greatly increase your risk of breast cancer and other cancers, but they don’t make cancer inevitable.
- Radiation exposure. If you received radiation treatments to your chest as a child or young adult, your risk of breast cancer is increased.
- Obesity. Being obese increases your risk of breast cancer.
- Beginning your period at a younger age. Beginning your period before age 12 increases your risk of breast cancer.
- Beginning menopause at an older age. If you began menopause at an older age, you’re more likely to develop breast cancer.
- Having your first child at an older age. Women who give birth to their first child after age 30 may have an increased risk of breast cancer.
- Having never been pregnant. Women who have never been pregnant have a greater risk of breast cancer than do women who have had one or more pregnancies.
- Postmenopausal hormone therapy. Women who take hormone therapy medications that combine estrogen and progesterone to treat the signs and symptoms of menopause have an increased risk of breast cancer. The risk of breast cancer decreases when women stop taking these medications.
- Drinking alcohol. Drinking alcohol increases the risk of breast cancer.
A doctor often diagnoses breast cancer as the result of routine screening or when a woman approaches her doctor after detecting symptoms.
Several diagnostic tests and procedures help to confirm a diagnosis.
The doctor will check the breasts for lumps and other symptoms.
During the examination, the person may need to sit or stand with their arms in different positions, such as above their head or by their sides.
Several tests can help detect breast cancer.
Mammogram: This is a type of X-ray that doctors commonly use during an initial breast cancer screening. It produces images that can help a doctor detect any lumps or abnormalities.
A doctor will usually follow any suspicious results with further testing. However, mammography sometimes shows a suspicious area that turns out not to be cancer.
Ultrasound: This scan uses sound waves to help a doctor differentiate between a solid mass and a fluid-filled cyst.
MRI: Magnetic Resonance Imaging (MRI) combines different images of the breast to help a doctor identify cancer or other abnormalities. A doctor may recommend an MRI as a follow-up to a mammogram or ultrasound. Doctors sometimes use them as a screening tool for those at higher risk of breast cancer.
In a biopsy, the doctor extracts a sample of tissue and sends it for laboratory analysis.
This shows whether the cells are cancerous. If they are, a biopsy indicates which type of cancer has developed, including whether or not the cancer is hormone sensitive.
Diagnosis also involves staging the cancer to establish:
- The size of a tumor
- How far it has spread
- Whether it is invasive or noninvasive
Staging provides a picture of a person’s chances of recovery and their ideal course of treatment.
Treatment will depend on several factors, including:
- The type and stage of the cancer
- The person’s sensitivity to hormones
- The age, overall health, and preferences of the individual
The main treatment options include:
- Biological therapy, or targeted drug therapy
- Hormone therapy
Factors affecting the type of treatment a person has will include the stage of the cancer, other medical conditions, and their individual preference.
If surgery is necessary, the type will depend on both the diagnosis and individual preference. Types of surgery include:
Lumpectomy: This involves removing the tumor and a small amount of healthy tissue around it.
A lumpectomy can help prevent the spread of the cancer. This may be an option if the tumor is small and easy to separate from its surrounding tissue.
Mastectomy: A simple mastectomy involves removing the lobules, ducts, fatty tissue, nipple, areola, and some skin. In some types, a surgeon will also remove the lymph nodes and muscle in the chest wall.
Sentinel node biopsy: If breast cancer reaches the sentinel lymph nodes, which are the first nodes to which a cancer can spread, it can spread into other parts of the body through the lymphatic system. If the doctor does not find cancer in the sentinel nodes, then it is usually not necessary to remove the remaining nodes.
Axillary lymph node dissection: If a doctor finds cancer cells in the sentinel nodes, they may recommend removing several lymph nodes in the armpit. This can prevent the cancer from spreading.
Reconstruction: Following mastectomy, a surgeon can reconstruct the breast to look more natural. This can help a person cope with the psychological effects of breast removal.
The surgeon can reconstruct the breast at the same time as performing a mastectomy or at a later date. They may use a breast implant or tissue from another part of the body.
A person may undergo radiation therapy around a month after surgery. Radiation involves targeting the tumor with controlled doses of radiation that kill any remaining cancer cells.
A doctor may prescribe cytotoxic chemotherapy drugs to kill cancer cells if there is a high risk of recurrence or spread. When a person has chemotherapy after surgery, doctors call it adjuvant chemotherapy.
Sometimes, a doctor may choose to administer chemotherapy before surgery to shrink the tumor and make its removal easier. Doctors call this neoadjuvant chemotherapy.
Hormone Blocking Therapy
Doctors use hormone-blocking therapy to prevent hormone-sensitive breast cancers from returning after treatment. Hormone therapy may be used to treat estrogen receptor (ER)-positive and progesterone receptor (PR)-positive cancers.
They usually administer hormone blocking therapy after surgery but might sometimes use it beforehand to shrink the tumor.
Hormone blocking therapy may be the only option for people who are not suitable candidates for surgery, chemotherapy, or radiotherapy.
Doctors may recommend a person has hormone therapy for 5–10 years after surgery. However, the treatment will not affect cancers that are not sensitive to hormones.
Examples of hormone blocking therapy medications may include:
- Aromatase inhibitors
- Ovarian ablation or suppression
- Goserelin, which is a luteinizing hormone-releasing agonist drug that suppresses the ovaries
Hormone treatment may affect fertility.
Targeted drugs can destroy specific types of breast cancer. Examples include:
- Trastuzumab (Herceptin)
- Lapatinib (Tykerb)
- Bevacizumab (Avastin)
Treatments for breast and other cancers can have severe adverse effects. When deciding on a treatment, people should discuss the potential risks with a doctor and look at ways to minimize the side effects.