Breast Cancer: What It Is, Symptoms, Types, Stages & Treatments

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Breast cancer remains the number one diagnosed cancer in women in the United States, other than skin cancer, according to the American Society of Clinical Oncology (ASCO).

If you’re concerned about breast cancer affecting you or someone close to you, this article can help you learn more about:

  • How breast cancer starts in cells

  • The different types of breast cancer

  • Possible symptoms of breast cancer

  • How breast cancer is treated today

What is breast cancer? 

Breast cancer occurs when cells change and start multiplying out of control, creating a cancerous (malignant) mass, or tumor. Breasts are made up of several types of tissue, and cancer may start in any of them, but it most often starts in the ducts that transport milk to the nipple and the lobules that produce milk, according to the Centers for Disease Control and Prevention (CDC). The tissue where cancer begins is tied to the type of breast cancer that develops. 

According to the American Cancer Society (ACS), in addition to lobules and ducts, other types of breast tissue in which cancer may arise include:

  • Nipple

  • Stroma (the fat and connective tissue)

  • Lymph and blood vessels

What causes breast cancer? 

Why one individual gets cancer may not be known, and for many, there is no inherited or personal risk factor that helps explain why cancer occurred. However, there are some things that seem to be tied to breast cancer risk.

According to ASCO, several factors are associated with a higher risk of developing breast cancer. They may include:

  • Being female

  • Age (the majority of breast cancer cases occur in women 50 or older)

  • Previous history of breast cancer

  • Family history of breast cancer

  • Ethnicity and race. White women are diagnosed at higher rates than Black women, but among women younger than 45, breast cancer occurs more often in Black women than white women. Black and Hispanic women are often diagnosed at more advanced stages of cancer than white women. Ashkenazi Jewish ancestry raises risk.

  • Some genetic mutations, notably BRCA1 and BRCA2, and also PALB2

  • Some hereditary conditions, including Lynch syndrome and Li-Fraumeni syndrome

  • Menstruation that began before age 11 or 12

  • Menopause that began after age 55

  • Postmenopausal hormone replacement therapy 

  • First pregnancy after age 35

  • Having dense breasts

  • Being overweight or obese

  • Low amount of regular exercise

  • Drinking more than 1 to 2 servings of alcohol a day

A strong family history refers to:

  • One or more female relatives diagnosed with breast cancer before age 45

  • A female relative diagnosed with a second breast cancer or breast and ovarian cancer

  • One or more female relatives diagnosed with breast cancer before age 50, along with a family history of some other cancers, including ovarian and metastatic prostate cancer and pancreatic cancer

  • Occurrence of breast cancer and ovarian cancer on either parent’s side

  • A male relative diagnosed with breast cancer

Can men develop breast cancer?

Yes, men may develop breast cancer, too, although it’s more rare compared to women. According to the CDC, for every 100 cases of breast cancer in the U.S., one is male. These additional factors may also increase male breast cancer risk:

  • Cirrhosis of the liver

  • Radiation therapy

  • Estrogen therapy

  • Testicular conditions such as Klinefelter syndrome, when a man has a second X chromosome

Breast cancer symptoms 

Symptoms of breast cancer vary from person to person, and some people have no signs of breast cancer before being diagnosed. According to the CDC, breast cancer may give rise to these symptoms:

  • Lump in breast or armpit

  • Swelling or distension of a portion of a breast, or any change in size or shape

  • Dimpling of breast skin

  • Redness, irritation or flaking of breast skin or nipple

  • Nipple becomes flatter or inverted

  • Blood or discharge (other than milk) from nipple

  • Pain in nipple or other area of the breast

Types of breast cancer 

Breast cancers are most often carcinomas, arising from the type of cells that line the organs and vessels in your body. Cancers that start in the cells of the milk ducts or lobules are a subset of carcinomas called adenocarcinoma, according to the ACS.

Ductal carcinoma in situ (DCIS) breast cancer

This is when cancer cells form in the lining of the milk ducts and have not spread into neighboring tissue. About one-fifth of newly diagnosed cases of breast cancer are DCIS, and most cases may be cured, according to the ACS

Invasive vs. noninvasive breast cancer

DCIS is considered either noninvasive or preinvasive, meaning it hasn’t spread or hasn’t yet spread to nearby tissue.

Invasive breast cancer has grown from the original site into nearby tissue. Up to 80% of invasive breast cancers start in the ducts and the lobules, according to ACS.

Triple-negative breast cancer

This cancer accounts for about 10 to 15% of breast cancers, according to ACS. It’s called triple-negative because these cancer cells lack receptors for the hormones estrogen and progesterone, and they don’t produce much of the protein HER2. These characteristics make it harder to treat. 

Inflammatory breast cancer (IBC)

This rare cancer accounts for 1 to 5% of new breast cancer cases, according to ACS. It causes the breasts to appear inflamed, red and swollen. IBC is harder to diagnose because it doesn’t always form a lump, and it may not appear on a mammogram. Typically, this aggressive cancer has already spread into the skin when diagnosed.

Other breast cancers

Each of these other, rare breast cancer types account for less than 3% of all breast cancers:

  • Paget disease of the breast

  • Angiosarcoma

  • Phyllodes tumor

Stages of breast cancer 

Staging is a method doctors use to define characteristics of the cancer, and it may be done before or after surgery to remove cancer. Staging helps guide treatment and predict prognosis. One system often used to stage cancer is called the TNM staging system. The letters T, N and M stand for:

  • T: What is the tumor size and are there special biomarkers (genes and substances associated with cancer cells)?

  • N: Has the cancer spread to lymph nodes (pockets of tissue in the armpits and and other areas that help drain fluid) and to what degree?

  • M: Has the cancer spread (metastasized) to distant parts of the body?

Each of these factors are measured and combined to create a TNM stage. According to ASCO, under the TNM system, there are five overall stages of breast cancer progression, ranging from 0 to 4. The letters A, B and C sometimes follow the stage number and further specify the stage. In general, the five breast cancer stages based on TNM measurements include the following.

Stage 0 breast cancer: Cancer has not spread from the ducts (Tis, N0, M0).

Stage 1 breast cancer, divided into 1A and 1B: Early breast cancer that is relatively contained in the duct lining or has very little spread to lymph nodes.

Stage 2 breast cancer, divided into 2A and 2B: Cancer is found in a small breast tumor or lymph nodes in the armpits.

Stage 3 breast cancer, divided into 3A, 3B and 3C: Cancer tumor is larger than Stage 2, may have moved into the chest wall, and cancerous cells have spread to some breast, armpit, and nearby lymph nodes.

Stage 4 (metastatic breast cancer): Tumor is of any size, and cancer has spread to organs and tissues outside of the breast.

Recurrent breast cancer: Cancer that has returned after treatment. 

Breast cancer tests 

Several methods are used to diagnose breast cancer, according to the CDC. These may include:

Mammograms: This method uses X-rays to create sharp images of the breast.

Ultrasound (sonogram): This method uses sound waves to create images of the interior of your breast.

MRI (magnetic resonance imaging): Uses very strong magnets and radio waves to make detailed images.

Breast biopsy: A few different methods are available to extract fluid or tissue for laboratory examination. 

Breast cancer treatments 

Treatment for breast cancer may take many forms, which may be done one at a time or in combination, depending upon the type of cancer, its stage, and the health and age of the patient. 

Breast cancer surgery often follows shortly after diagnosis to remove as much cancerous tissue as may be removed, according to ACS. It may be: 

  • Breast-conserving surgery (lumpectomy): The goal is to remove the tumor and some of the surrounding tissue.

  • Mastectomy: One or both breasts are removed. 

  • Sentinel lymph node biopsy: One or more of the axillary lymph nodes may be biopsied to check for the presence of cancer cells.

  • Axillary lymph node dissection: Less common than sentinel lymph node biopsy. Up to 20 axillary nodes may be removed.

  • Reconstruction: Done to restore breast appearance after surgery.

  • Other surgeries may be performed to remove metastases from other organs or provide symptomatic relief in advanced cancer.

Radiation therapy includes external beam radiation therapy and brachytherapy. These treatments utilize X-rays or other radiation waves or particles to destroy cancer cells in the breast with a targeted procedure.

Chemotherapy uses chemicals that destroy cancer cells and other fast-growing cells, such as hair follicles. It’s systemic, meaning the drugs travel throughout the body. These drugs may be given as pills, but more often they’re injected into a vein and given slowly as an intravenous (IV) infusion. According to ACS, chemotherapy may be given after surgery (adjuvant), when it may help destroy traces of cancer, or before surgery (neoadjuvant), which may be done to shrink a tumor before surgery, or because many lymph nodes are affected or the breast cancer is inflammatory.

Hormone therapy attempts to block or limit the hormones estrogen and progesterone from feeding the growth of breast cancer, a contributing factor for about 66% of breast cancers, according to ACS. Treatment typically begins after surgery and may extend for 5 years or more.

Immunotherapy drugs enhance the body’s immune system and help it fight off cancer. They’re usually given by infusion. One type of immunotherapy drug is called a checkpoint inhibitor, which helps to restore the immune response against cancer cells, according to ACS.

Targeted therapy drugs seek out specific proteins and substances on cancer cells, such as HER2, and interfere with its growth in some way. Like chemotherapy, these drugs are systemic throughout the body. According to ACS, examples of targeted therapy drug categories for breast cancer include:

  • Monoclonal antibodies

  • Antibody-drug conjugates

  • Kinase inhibitors

Breast cancer screening

Screening refers to tests and procedures to look for cancer before being diagnosed with the disease. Many experts, such as ACS and CDC recommend mammography as the main screening tool for breast cancer. Mammography uses X-rays to look at internal breast tissue and may find tumors too tiny to be felt, including ductal carcinoma in situ.

According to ACS, women at average risk should follow these guidelines:

  • Women between 40 and 44 may start screening with a mammogram every year.

  • Women 45 to 54 should get mammograms every year.

  • Women over 55 may switch to a mammogram every other year, or they may choose to continue yearly mammograms. 

  • Clinical breast exams are no longer recommended for breast cancer screening among average-risk women at any age.

Other screening methods such as MRI may also be recommended for those at high risk.

Breast cancer survival rate 

The National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) program collects data on cancer cases and estimates 5-year relative survival rates. These rates reflect the percentage of people with cancer expected to live 5 years after diagnosis based on past treatments and data. However, each individual is different.

For all women with any type or stage of breast cancer, about 91% are expected to live at least 5 years after diagnosis, based on SEER data from 2013 to 2019.

The SEER program also calculates survival rates by these general stages:

  • Localized (contained in one place), about 99% (63% of cases)

  • Regional (some nearby spread), about 86% (28% of cases)

  • Distant (spread to faraway nodes or organs), about 31% (6%of cases)

The remaining 3% (unstaged) has a 5-year relative survival rate of about 70%.

Living with breast cancer

Being diagnosed and treated for breast cancer changes your life. It has physical, mental, emotional, sexual, social and financial implications. It may be exhausting and debilitating. It may also connect you to new people and give you a positive perspective on life. 

Side effects from treatment may be short-lived or long-lasting. Coping with them may be made easier by seeking the aid of a solid health team to help relieve bothersome symptoms.

You may also be interested in pursuing alternative and complementary health treatments, such as acupuncture, meditation or massage. The National Cancer Institute notes that some of these may help with side effects, but should be discussed with your healthcare provider, along with other treatments and therapies.

A healthy lifestyle with a nutritious diet and regular exercise, as well as not smoking and reducing alcohol consumption, may also help you be the best mentally and physically that you can be.

Support groups or online groups may provide places for you to discuss your thoughts with other cancer survivors. So can confiding with family, close friends or a therapist. Financial and insurance advice is available to assist with medicines and other expenses associated with cancer. Ask your healthcare provider and insurance plan. 


American Society of Clinical Oncology: Breast Cancer: Statistics.
Centers for Disease Control and Prevention: What is Breast Cancer?
American Cancer Society: What is Breast Cancer?
American Society of Clinical Oncology: Breast Cancer: Risk Factors and Prevention.
Centers for Disease Control and Prevention: Breast Cancer in Men.
Centers for Disease Control and Prevention: Breast Cancer. What Are the Symptoms?
American Cancer Society: Types of Breast Cancer.
American Cancer Society: Ductal Carcinoma in Situ.
American Cancer Society: Inflammatory Breast Cancer.
American Cancer Society: Paget Disease of the Breast.
American Cancer Society: Angiosarcoma of the Breast.
American Cancer Society: Phyllodes Tumors of the Breast.
American Society of Clinical Oncology: Breast Cancer: Stages.
American Cancer Society: Biomarker Tests and Cancer Treatment.
StatPearls: Anatomy, Shoulder and Upper Limb, Axillary Lymph Nodes.
Centers for Disease Control and Prevention: Breast Cancer, How Is Breast Cancer Diagnosed?
National Cancer Institute: Breast Cancer Screening (PDQ) – Patient Version.
National Breast Cancer Foundation: Breast Biopsy.
American Cancer Society: Surgery for Breast Cancer.
American Cancer Society: Chemotherapy for Breast Cancer.
American Society of Clinical Oncology: What is Chemotherapy?
American Cancer Society: Hormone Therapy for Breast Cancer.
American Cancer Society: Immunotherapy for Breast Cancer.

American Cancer Society: Targeted Drug Therapy for Breast Cancer.
National Cancer Institute, Surveillance, Epidemiology and End Results (SEER) Program: Cancer Stat Facts: Female Breast Cancer.
Susan G. Komen: Quality of Life After Breast Cancer Treatment.
National Cancer Institute: Complementary and Alternative Medicine.
American Society of Clinical Oncology: Breast Cancer – Metastatic: Living With Metastatic Breast Cancer.
Susan G. Komen: Financial Assistance.

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