Breast cancer is the most common invasive cancer in women and the second leading cause of cancer death in women after lung cancer.

Advances in screening and treatment for breast cancer have improved survival rates dramatically since 1989. According to the American Cancer Society (ACS), there are more than 3.1 million breast cancer survivors in the United States. The chance of any woman dying from breast cancer is around 1 in 38 (2.6%).

The ACS estimate that 268,600 women will receive a diagnosis of invasive breast cancer, and 62,930 people will receive a diagnosis of noninvasive cancer in 2019.

In the same year, the ACS report that 41,760 women will die as a result of breast cancer. However, due to advances in treatment, death rates from breast cancer have been decreasing since 1989.

Awareness of the symptoms and the need for screening are important ways of reducing the risk. In rare instances, breast cancer can also affect men, but this article will focus on breast cancer in women. Learn about breast cancer in men here.

Symptoms

The first symptoms of breast cancer usually appear as an area of thickened tissue in the breast or a lump in the breast or an armpit.

Other symptoms include

pain in the armpits or breast that does not change with the monthly cycle

pitting or redness of the skin of the breast, similar to the surface of an orange

a rash around or on one of the nipples

discharge from a nipple, possibly containing blood

a sunken or inverted nipple

a change in the size or shape of the breast

peeling, flaking, or scaling of the skin on the breast or nipple

Most breast lumps are not cancerous. However, women should visit a doctor for an examination if they notice a lump on the breast.

Stages

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 a 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: The cancer has spread to distant organs, most often the bones, liver, brain, or lungs.

Causes

After puberty, a woman’s breast consists of fat, connective tissue, and thousands of lobules. These are tiny glands that produce milk for breastfeeding. Tiny tubes, or ducts, carry the milk toward the nipple.

Cancer causes the cells to multiply uncontrollably. They do not die at the usual point in their life cycle. This excessive cell growth causes cancer because the tumor uses nutrients and energy and deprives the cells around it.

Breast cancer usually starts in the inner lining of milk ducts or the lobules that supply them with milk. From there, it can spread to other parts of the body.

Risk factors

The exact cause of breast cancer remains unclear, but some risk factors make it more likely. It is possible to prevent some of these risk factors.

1. Age

The risk of breast cancer increases with age. At 20 years, the chance of developing breast cancer in the next decade is 0.06%. By the age of 70 years, this figure goes up to 3.84%.

2. Genetics

Women who carry certain mutations in the BRCA1 and BRCA2 genes have a higher chance of developing breast cancer, ovarian cancer, or both. People inherit these genes from their parents.

Mutations in the TP53 gene also have links to increased breast cancer risk.

If a close relative has or has had breast cancer, a person’s chance of developing breast cancer increases.

Current guidelines recommend that people in the following groups seek genetic testing

those with a family history of breast, ovarian, fallopian tube, or peritoneal cancer

those in whose ancestry there is a history of breast cancer related to BRCA1 or BRCA2 gene mutations, for example, people with Ashkenazi Jewish ancestry

3. A history of breast cancer or breast lumps

Women who have previously had breast cancer are more likely to have it again than those who have no history of the disease.

Having some types of noncancerous breast lump increases the chance of developing cancer later on. Examples include atypical ductal hyperplasia or lobular carcinoma in situ.

Individuals with a history of breast, ovarian, fallopian tube, or peritoneal cancer should ask their doctors about genetic testing.

4. Dense breast tissue

Women with more dense breasts are more likely to receive a diagnosis of breast cancer.

Read more about dense breast tissue, here.

5. Estrogen exposure and breastfeeding

Extended exposure to estrogen appears to increase the risk of breast cancer.

This could be due to a person starting their periods earlier or entering menopause at a later than average age. Between these times, estrogen levels are higher.

Breastfeeding, especially for over 1 year, appears to reduce the chance of developing breast cancer. This is possibly due to the in estrogen exposure that follows pregnancy and breastfeeding.

6. Body weight

Women who become overweight or develop obesity after menopause may also have a higher chance of developing breast cancer, possibly due to increased estrogen levels. High sugar intake may also be a factor.

7. Alcohol consumption

A higher rate of regular alcohol consumption appears to play a role in breast cancer development.

According to the National Cancer Institute (NCI), studies have consistently found that women who consume alcohol have a higher risk of breast cancer than those who do not. Those who drink moderate to heavy levels of alcohol have a higher risk than light drinkers.

8. Radiation exposure

Undergoing radiation treatment for a different cancer may increase the risk of developing breast cancer later in life.

9. Hormone treatments

According to the NCI, studies have shown that oral contraceptives may slightly increase the risk of breast cancer

According to the ACS, studies have found that hormone replacement therapy (HRT), specifically estrogen-progesterone therapy (EPT), is related to an increased risk of breast cancer.

Cosmetic implants and breast cancer survival

A 2013 review found that women with cosmetic breast implants who received a diagnosis of breast cancer also had a higher risk of dying from the disease.

This could be due to the implants masking cancer during screening or because the implants bring about changes in breast tissue.

However, a 2015 review published in Aesthetic Surgery Journal found that having cosmetic breast implant surgery did not increase the risk of breast cancer.

Scientists need to carry out more research to confirm the link.

Types

There are several different types of breast cancer, including

Ductal carcinoma: This begins in the milk duct and is the most common type.

Lobular carcinoma: This starts in the lobules.

Invasive breast cancer occurs when the cancer cells break out from inside the lobules or ducts and invade nearby tissue. This increases the chance of cancer spreading to other parts of the body.

Noninvasive breast cancer develops when the cancer remains inside its place of origin and has not yet spread. However, these cells can sometimes progress to invasive breast cancer.

Diagnosis

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.

Breast exam

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.

Imaging tests

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.

Here, learn more about how to prepare for a mammogram.

Biopsy

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

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

radiation therapy

surgery

biological therapy, or targeted drug therapy

hormone therapy

chemotherapy

Factors affecting the type of treatment a person has will include the stage of the cancer, other medical conditions, and their individual preference.

Surgery

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.

Here, learn about the different types of mastectomy.

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.

Find out more about breast reconstruction su