Breast Cancer: Defining the Disease

Get an overview on what breast cancer is, how it’s diagnosed, and what symptoms to look for.

Know the facts

What is breast cancer?

Breast cancer is a disease in which cells in the breast grow out of control and form tumors. In most instances, these tumors can be felt as a lump. Type, stage, grade, and hormone receptor status are just a few ways to classify breast cancer.

TYPE AND SUBTYPE

Type refers to where the cancer has started, along with other factors. The most common breast cancer types are ductal and lobular. Ductal means that the cancer began in the milk ducts. Lobular means that the cancer began in the milk-producing glands. Each of these types has 2 subtypes: in situ and invasive. In situ means that the cancer has not spread. Invasive means that the cancer has spread to nearby tissue in the breast. Below is a list of the most common types and subtypes of breast cancer.

Ductal
Ductal carcinoma in situ (DCIS)

About 1 in 5 new breast cancers will be DCIS. This is considered a noninvasive or pre-invasive breast cancer.

Invasive ductal carcinoma (IDC)

This is the most common type of breast cancer and is invasive. IDC starts in the milk duct of the breast, breaks through the wall of the duct, and grows into the fatty tissue of the breast.

Lobular
Lobular carcinoma in situ (LCIS)

This is considered to be more of a breast change than a breast cancer. The cells that look like cancer cells are growing in the lobules, which are glands in the breast that are responsible for making milk, but they don’t grow through the walls of the lobules.

Invasive lobular carcinoma (ILC)

ILC is an invasive cancer that starts in the lobules and can spread to other parts of the body.

STAGE

The stage of the cancer refers to how far it has spread from the breast to other parts of the body. Breast cancer is divided into 5 stages. Staging is an important part of the process because accurate staging can help determine treatment.

The changes in the cells are considered precancer and have not spread to the lymph nodes.

 

The cancer is invasive and has spread to normal breast tissue, but not to distant sites.

Subgroups
  • IA:The tumor is 2 centimeters or less across and has not spread to the lymph nodes.
  • IB:The tumor is 2 centimeters or less across (or is not found) and has spread minimally to the lymph nodes in the underarm.
 

The cancer is invasive and has spread to nearby lymph nodes, but not to distant sites.

Subgroups
  • IIA: •The tumor is 2 centimeters or less across (or is not found) and has spread to the lymph nodes underneath the arm
  • The tumor is larger than 2 centimeters, but is less than 5 centimeters across and has not spread to the lymph nodes
  • IIB: •The tumor is larger than 2 centimeters, but is less than 5 centimeters across. It has spread to the lymph nodes underneath the arm, and/or small amounts of cancer are found in the lymph nodes near the breastbone
  • The tumor is larger than 5 centimeters across, but does not grow into the chest wall or skin and has not spread to the lymph nodes
 

The cancer is considered to be locally advanced, which means that it has spread to nearby tissues or lymph nodes, but not to distant sites.

Subgroups
  • IIIA: •The tumor is not larger than 5 centimeters across (or is not found) and has spread to lymph nodes clumped together underneath the arm or near the breastbone
  • The tumor is larger than 5 centimeters across, but does not grow into the chest wall or skin. It has spread to lymph nodes underneath the arm or near the breastbone
  • IIIB: The tumor has grown into the chest wall or skin and has not spread to the lymph nodes, or it has spread to some or many lymph nodes underneath the arm or near the breastbone.
  • IIIC: The tumor is any size (or is not found) and the cancer has spread to many lymph nodes underneath the arm, or under the collarbone, or underneath the arm and near the breastbone.
 

The cancer can be any size and may or may not have spread to nearby lymph nodes. It has spread to distant organs, such as the bones, liver, brain, or lungs. This stage is also called advanced breast cancer or metastatic breast cancer.

 

GRADE

Grade is a way to describe the look of cancer cells when compared with healthy cells.

Grade 1:

Cells look more like normal cells and are growing slowly.

Grade 2:

Cells look and act somewhere in between Grade 1 and Grade 3.

Grade 3:

Cells look very different from normal cells and are growing quickly.

RECEPTOR STATUS

During biopsy or surgery, breast cancer cells can be tested to see if they have certain receptors that fuel cancer growth. The 3 main types of receptors that doctors look at are estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2.

Estrogen
Receptor (ER)

An ER is a protein found on the cell surface that can bind to estrogen to help cells grow. ER-positive means that the cancer has ERs. If the cancer does not have any ERs, it’s considered ER-negative.

Progesterone
Receptor (PR)

A PR is a protein found on the cell surface that can bind to progesterone to help cells grow. PR-positive means that the cancer has PRs. If the cancer does not have any PRs, it’s considered PR-negative.

Human Epidermal Growth Factor
Receptor 2 (HER2)

HER2 is a protein found on the cell surface that normally helps control cell growth. HER2-positive cancer has too much HER2. HER2-negative cancer does not have an excessive amount of HER2.

 

Triple-negative

Breast cancer that is ER-negative, PR-negative, and HER2-negative is called triple-negative breast cancer. This type of breast cancer grows and spreads faster than other types of breast cancer.

Other breast cancers that test positive for hormone receptors may receive hormonal therapy. Triple-negative breast cancer tests negative for hormone receptors, meaning it cannot be treated effectively with hormonal therapy.

Who can get breast cancer?

Both men and women can get breast cancer, but women are more likely to develop the disease. Aside from skin cancer, breast cancer is the most common cancer in American women. This year alone, more than 252,000 women will learn that they have invasive breast cancer. Certain women may have high risk factors, such as inherited mutations or a family history of breast cancer.

How is breast cancer diagnosed?

There are several ways to diagnose breast cancer. Mammograms, ultrasounds, and magnetic resonance imaging (MRI) scans are tests that look for breast cancer. If any of these tests show signs of breast cancer, then a breast biopsy is done to confirm whether or not cancer is present.

Early diagnosis can lead to better outcomes

Finding breast cancer before it spreads is critical because it’s easier to treat successfully. Regular screenings, such as mammograms, are the most reliable way to find breast cancer early.

Signs and symptoms of breast cancer

It’s important to recognize the signs and symptoms of breast cancer. Finding breast cancer early leads to a better chance of successful treatment.

Signs and symptoms can include:

A new lump or mass in the breast

Swelling of all or part of the breast

Breast or nipple pain

Nipple retraction

Redness, scaliness, or thickening of the nipple or breast skin

Nipple discharge

A new lump or swelling in the lymph nodes under the arm or near the collarbone