Breast Cancer Diagnosis and Staging

April 10, 2025

This page was reviewed under our medical and editorial policy by Susan Yost, Ph.D., staff scientist, Department of Medical Oncology & Therapeutics Research, City of Hope^® Cancer Center Duarte

If breast cancer is suspected, a diagnosis typically begins with a physical examination and imaging in order to pinpoint the area of concern. If a breast lump or other signs are found, the care team will likely order a biopsy to obtain a tissue sample for examination under a microscope. More tests may also be needed to learn more about the cancer and its characteristics.

All of the information found during testing factors into a patient’s treatment plan.

Tests for Breast Cancer

The care team may use results from several types of tests to diagnose breast cancer. Other tests may also be used to stage breast cancer — that is, to determine the extent of the cancer and where it is in the body. Tests that may be used include the following.

Mammogram: This is a low-dose X-ray of the breasts. In a patient with breast cancer symptoms, a diagnostic mammogram is used. It typically includes extra views of the breast that are usually not included in a regular screening mammogram.

Breast ultrasound: This imaging test uses sound waves to create a digital picture of the inside of the breast. It might be used to obtain greater detail when a mammogram shows a suspicious area, or it may be used during a biopsy to help zero in on the exact location for tissue removal.

Breast magnetic resonance imaging (MRI): In this imaging test, the patient lies face down on a table, which then slides into the MRI machine. The machine uses radio waves and strong magnets to create a digital picture of the inside of the breast. This test may be used when images from other types of tests are not as clear.

Breast biopsy: With a biopsy, some tissue is removed to test the cells for the presence of cancer, or to learn more about a cancer. There are several types of biopsies, depending on how much tissue is needed for analysis. A thin needle may be used to obtain a small sample of tissue or fluid (fine needle aspiration biopsy), or a wide needle may be used to obtain a larger sample (core biopsy). Sometimes, part or all of a lump is removed.

These are not the only tests that are used in breast cancer diagnosis and staging, but they are the most common. Newer tests are being evaluated to determine if they are as helpful as the more common tests above.

Once cancer is diagnosed, the following tests may be used to learn more about it and help the care team develop an appropriate treatment plan.

Estrogen and progesterone hormone receptor test: This test checks cancer cells removed during a biopsy or surgery for elevated levels of receptors for the hormones estrogen and progesterone. If the cancer is determined to be estrogen and/or progesterone receptor positive, hormone therapy drugs may be prescribed.

Human epidermal growth factor type 2 receptor (HER2/neu) test: This test requires a sample of blood or other body tissue to look for the HER2/neu gene and the high levels of the HER2/neu protein. Cancers that are HER2/neu positive may be fast-growing and are more likely to spread, and a treatment plan may include drugs that specifically target the HER2/neu protein.

Multigene tests: These tests use a sample of blood or other body tissue to look at many genes at the same time. Knowing more about specific genes helps the care team determine if the cancer is apt to spread or may be likely to recur after treatment.

Breast Cancer Stages

Staging for breast cancer helps doctors understand a cancer’s size, location in the body and whether or not it has spread, as well as other characteristics — such as hormone receptor status — in order to plan the appropriate treatment and gauge long-term survival.

Breast cancer staging includes both a clinical and a pathologic stage. This is determined by the type of information the care team has about the cancer.

Clinical stage is determined by studying results of tests done before surgery. These tests may include mammograms, ultrasounds, MRI, biopsies, X-rays, computed tomography (CT) scans, positron emission tomography (PET) scans or bone scans. It may provide a less reliable gauge of a patient’s overall survival odds.

Pathologic stage is generally considered more accurate. It is determined after studying breast or lymph node tissue removed during surgery and provides the care team with more information.

The TNM Staging System

The American Joint Committee on Cancer’s TNM system is used to stage breast cancer.

TNM stands for tumor, lymph nodes and metastasis. Additional letters and/or numbers after each of these letters represent details about the cancer’s size, location and spread.

Tumor (T): This measures the size of the tumor.

Lymph nodes (N): This indicates whether the cancer has spread into lymph nodes — and if so, into how many.

Metastasis (M): This describes whether the cancer has spread to distant areas of the body, such as the bones or brain.

Four other characteristics are also determined during the breast cancer staging process:

• How much the cancer cells resemble normal cells (grade)
• Estrogen receptor (ER) status
• Progesterone receptor (PR) status
• HER2 protein status

Stage 0

Stage 0 breast cancer is also called carcinoma in situ. It has not spread beyond the breast lobules or ducts, though it may spread in the future.

Stage 1

The cancer may be too small to see, but it is invasive, meaning it has begun to spread. Stage 1 breast cancer may have reached nearby lymph nodes.

Stage 2

In Stage 2 breast cancer, cancer cells may be in nearby lymph nodes and not in the breast itself; there may be a 2- to 5-centimeter tumor in the breast and cancer in some nearby lymph nodes; or there may be a tumor in the breast larger than 5 centimeters in size, but no cancer in nearby lymph nodes.

Stage 3

Stage 3 breast cancer is divided into three substages.

Stage 3a: Cancer has spread to between four and nine nearby lymph nodes; or there is a tumor larger than 5 centimeters in the breast with spread to three lymph nodes.

Stage 3b: The tumor has grown in the chest wall or skin, which may cause swelling or an ulcer. Cancer may have also spread to nearby lymph nodes.

Stage 3c: Cancer has spread to 10 or more nearby lymph nodes, and possibly into the chest wall or skin, but it has not gone beyond.

Stage 4

Cancer has spread outside the area of the breast to distant organs. In breast cancer, this often means the bones, brain, liver or lungs. Stage 4 is also called metastatic breast cancer.