Once breast cancer is diagnosed, it is graded and staged. The grade describes the appearance of the biopsied cancer cells under the microscope, and the stage describes the likely pattern of growth and spread of the cancer. Staging predicts how aggressive a cancer will be and helps the oncologist recommend the most effective breast cancer treatment. Grade is a factor in staging.

Grades of Breast Cancer

The grade of a tumor is an expression of how its cells appear under a microscope. Invasive tumors are graded 1 (low), 2 (medium), or 3 (high) by how much they look and grow like normal cells, in a regular and organized fashion. A low grade means that the cells are closer to normal, and more likely to grow slowly. Higher grades of cells are irregular and disorganized and may grow more quickly. Oncologists also describe low-grade tumors as well-differentiated, meaning they look and grow much like they should, or poorly differentiated, meaning they appear abnormal and grow in an unusual pattern.

Noninvasive (in situ) tumors may be described as low, medium, or high, rather than numbered 1 through 3. Read more about types of tumors.

The grade of a tumor can be found in the pathology report.

Stages of Breast Cancer

Traditionally, breast cancer was staged based on three factors: the size of the primary (original) tumor, the number of lymph nodes the cancer had spread to, and whether or not the tumor had metastasized – spread to other parts of the body such as the lungs, brain, bones, or liver. In 2018, the American Joint Committee on Cancer published new criteria that include additional characteristics to be considered: the grade of the tumor and the molecular subtype (read more about types of cancer and hormone receptor status). Molecular subtypes are determined using a test called Oncotype DX during the process of breast cancer diagnosis. Staging may also depend on whether surgery or another treatment approach is used first.

A prognosis is a forecast of how the disease will proceed and how many years the person will survive. Oncologists base an individual’s prognosis on the grade, stage, and type of their breast cancer and how thousands of similar cases of breast cancer have proceeded and responded to treatment. Generally, a more advanced stage means a poorer prognosis. More advanced stages of breast cancer are harder to treat. However, there are effective treatments for each stage of breast cancer.

In rare circumstances, breast cancer may be restaged to evaluate the effectiveness of treatment or assess a case of cancer that recurs after treatment. In most cases, the stage that was originally assessed remains in effect.

Stage 0

Extremely early cancer may be called stage 0. Stage 0 breast cancer is noninvasive. There are atypical cells, but they have not spread outside their tissue of origin. Stage 0 may be referred to as carcinoma in situ. It is very difficult to detect stage 0 breast cancer. Carcinoma in situ is sometimes found accidentally when breast tissue is biopsied for unrelated reasons, such as the investigation of a benign lump. Stage 0 breast cancer is usually very easy to treat.

Read more about stage 0 breast cancer.

Stage 1

In stage 1, cancer is easier to detect. If there is a tumor, it is very small, and if any lymph nodes are affected, they have tiny amounts of cancer cells. Stage 1 cancer is considered invasive – cancer cells have just barely begun to spread to adjacent breast tissues. Stage 1 may be further divided into 1A and 1B depending on the size of the tumor, whether lymph nodes are involved, and the grade and molecular subtype of the cancer cells. Stage 1 breast cancer is very treatable.

Read more about stage 1 breast cancer.

Stage 2

Breast cancer may be classed as stage 2 if no tumor is found, but there are larger collections of cancer cells in the lymph nodes; or if there is a larger tumor, but no lymph node involvement. Depending on the size of the tumor, lymph node involvement, and other factors, stage 2 breast cancer may be classified as 2A or 2B. Stage 2 breast cancer requires a more aggressive treatment approach, but usually responds well to treatment.

Read more about stage 2 breast cancer.

Stage 3

Stage 3 breast cancer may involve either a larger tumor or the spread of cancer cells as far as the skin or the lymph nodes under the arm or close to the sternum (breastbone). Stage 3 breast cancer is considered advanced. Substages 3A, 3B, and 3C are assigned based on the size of the tumor, the spread of the cancer, and specific characteristics of the cell. Stage 3 breast cancer is usually treated with a combination of techniques that depend on the substage and type of the cancer.

Read more about stage 3 breast cancer.

Stage 4

In stage 4 breast cancer, cancer cells have spread from the breast to other parts of the body, a process known as metastasis. Breast cancer most commonly metastasizes to the liver, lungs, brain, or bones. Breast cancer metastases (or mets) may also be found in distant lymph nodes or embedded in the chest wall. In 5 percent or 6 percent of women, breast cancer is first detected when it is in stage 4 — in these cases, breast cancer may be referred to as de novo.

Stage 4 breast cancer cannot be cured, but it is treatable. Metastatic breast cancer is often a chronic condition that requires ongoing or periodic treatment control. It may go into remission and later return.

Read more about stage 4 breast cancer.

Condition Guide

• Breast Cancer – An Overview
• Breast Cancer Symptoms
• Breast Cancer – The Path to Diagnosis
• Breast Cancer Treatment
• Side Effects of Breast Cancer Treatments
• Types of Breast Cancer
• What Causes Breast Cancer?