What Are the Stages and Grades of Breast Cancer?

Medically Reviewed by Jennifer Robinson, MD on March 17, 2023
5 min read

If you've been diagnosed with breast cancer, you’ll want to know what stage and grade it is. The answers will help you and your doctors know more about what’s ahead and decide on your treatments.

Doctors have many ways to find out what stage of breast cancer you have. Clues come from physical exams, biopsies, X-rays, bone scans and other images, and blood tests. A doctor called a pathologist puts tissue samples from the breast and lymph nodes under the microscope to find out even more.

Based on these findings, doctors string together letters and numbers to assign a stage to every case of breast cancer. It may seem like a strange code, but it’s really just a way to pinpoint exactly what’s going on with your cancer. Think of it like this: The longer the list of letters and numbers, the more exact the diagnosis and the more precise the treatment plan.

The stages are the number zero and the Roman numerals I, II, III, or IV (often followed by A, B, or C). In general, the higher the number, the more advanced the cancer. But there’s more to it than that.

Stage 0. The cancer has been diagnosed early. It started in the breast ducts or milk glands and has stayed there. You’re likely to hear or see the words in situ, meaning “in the original place.” Get more details about stage 0 breast cancer types and treatment options.

Stage I. Starting at this level, breast cancer is called invasive, meaning it has broken free to attack healthy tissue.

Stage 1A means the cancer has spread into the fatty breast tissue. The tumor itself is no larger than a shelled peanut, or there may be no tumor.

Stage IB means some cancer cells, but just tiny amounts, have been found in a few lymph nodes.

Learn more about stage I breast cancer treatment.

Stage II. The cancer has grown, spread, or both.

IIA means the tumor in the breast is still small, if there's one at all. There may be no cancer in the lymph nodes, or it may have spread to as many as three.

A stage IIB breast tumor is bigger -- it may be the size of a walnut or as big as a lime. It may or may not be in any lymph nodes.

Read more on treatment options for stage II breast cancer.

Stage III. The cancer has not spread to bones or organs, but it’s considered advanced, and it’s harder to fight.

IIIA means the cancer has been found in up to nine of the lymph nodes that form a chain from your underarm to your collarbone. Or it has spread to or enlarged the lymph nodes deep in your breast. In some cases there is a large tumor in the breast, but other times there’s no tumor.

IIIB means the tumor has grown into the chest wall or skin around your breast, even if it hasn’t spread to the lymph nodes.

IIIC means cancer has been found in 10 or more lymph nodes, or has spread above or below your collarbone. It’s also IIIC if fewer lymph nodes outside the breast are affected but those inside it are enlarged or cancerous.

Get more information on stage III breast cancer treatment options.

Stage IV. Breast cancer cells have spread far away from the breast and lymph nodes right around it. The most common sites are the bones, lungs, liver, and brain. This stage is described as “metastatic,” meaning it has spread beyond the region of the body where it was first found.

Learn more about the types of treatment for stage IV breast cancer.

In addition to finding out the stage of your cancer, your doctor will want to know its grade. This is a way to measure how the cells look and how fast they’re growing compared to normal cells. It will also tell them how likely the cancer is to spread to other parts of your body. The stage and grade together will help them decide on a likely outcome for your cancer and the best treatment for you.

Doctors base a cancer cell’s grade on how different it looks from normal cells. They’ll look at three different features of the cells under a microscope and assign each one a score. They add these scores together to assign a grade of between 1 and 3:

  • Grade 1 (well differentiated): The cells look similar to normal breast tissue and are growing slowly.
  • Grade 2 (moderately differentiated): The cells look slightly different from normal cells and are growing slightly faster.
  • Grade 3 (poorly differentiated): The cells look very different from normal cells. They’re growing quickly and are likely to spread.

If you have Stage 0 ductal carcinoma in situ (DCIS), your doctors will grade the cells based on how they look. They’ll also look to see if dead or dying cancer cells are present. If there are, this means that they’re growing quickly. If there are a lot of dead or dying cancer cells, this means you have a higher grade of DCIS.

Doctors also group cancers by the letters T, N, or M. Each of those letters tells you something about your cancer.

T” stands for tumor, or the lump of cancer found in the breast itself. The higher the number assigned after it, the bigger or wider the mass.

N” stands for nodes, as in lymph nodes. These small filters are found throughout the body, and they're especially dense in and around the breast. They're meant to catch cancer cells before they travel to other parts of the body. Here, too, a number (0-III) tells you whether the cancer has spread to lymph nodes near the breast and, if so, how many.

M” stands for metastasis. The cancer has spread beyond the breast and lymph nodes.

The 5-year survival rate shows how many people live for at least 5 years after being diagnosed with breast cancer. It's based on the stage at the time of diagnosis. This rate is only an estimate, and some people will live much longer. The lower the stage, the better the chances of living longer. Your doctor can help you understand survival rates and what they mean for you.

According to the National Cancer Institute, the 5-year survival rates for breast cancer are:

Localized:  99%
Regional:  86%
Distant: 30%
All stages combined: 91%

A breast cancer diagnosis is a lot to take in. You’ll have questions. Tell your doctor when you don’t understand something. Let them know when you want more information. Find out more on breast cancer survival rates.