How is Breast Cancer Diagnosed?

This is the sixth page in the Understanding Breast Cancer Guide. This guide was developed by the HealthTree Education Team and was last updated and reviewed on May 18, 2026.

If your doctor thinks you may have breast cancer, there are several tests and procedures that can confirm a diagnosis. A single test is usually not enough. Diagnosis relies on a combination of your symptoms, a physical exam, and test results, including a biopsy.

This page lists all of the different tests that may be needed. Some are used to confirm a breast cancer diagnosis. Others are used to learn more about the cancer, such as genetic changes, that can help guide treatment. Some of these tests may also be used to monitor how well treatment is working. You may not have all of the tests on this list.

Talk to your care team if you have questions about which tests you received and what the results mean for your diagnosis.

Biopsy

A biopsy is the only way to confirm a diagnosis of breast cancer. During a biopsy, a small sample of tissue is removed from the breast and examined under a microscope. There are several types of biopsies:

• Core needle biopsy. The most common type. A hollow needle is used to remove small cylinders of tissue from the suspicious area.
• Fine needle aspiration (FNA). A thin needle is used to remove cells or fluid from a lump.
• Surgical biopsy. In some cases, a surgeon removes part or all of a lump for examination.

A pathologist then analyzes the sample to determine if cancer cells are present, and if so, what type of breast cancer it is. A pathologist is a doctor who specializes in studying cells and diagnosing diseases and other conditions.

Imaging tests to diagnose breast cancer

Imaging tests create pictures of the inside of the body and help doctors find and evaluate tumors:

• Mammography. Often the first imaging test used when breast cancer is suspected. A diagnostic mammogram (as opposed to a screening mammogram) takes more detailed images of the suspicious area.
• Breast ultrasound. Used to evaluate a specific area of concern found on a mammogram or physical exam. Ultrasound can distinguish between solid masses and fluid-filled cysts.
• Breast MRI. Provides detailed images of the breast and may be used to evaluate the extent of cancer, check the other breast, or screen high-risk women.
• Computed tomography (CT). A CT scan may be used to check whether breast cancer has spread to the lymph nodes, liver, lungs, or other areas.
• Positron emission tomography (PET). A PET scan can be used to check for cancer spread throughout the body.
• Bone scan. Used to check for spread of breast cancer to the bones.
• Chest X-ray. May be used to check whether cancer has spread to the lungs.

Blood tests to diagnose breast cancer

Blood tests used in the diagnosis and monitoring of breast cancer include:

• Complete blood count (CBC). Checks blood cell counts, which can be affected by cancer or treatment.
• Liver function tests. This test helps detect whether cancer may have spread to the liver
• Tumor markers such as CA 15-3 and CA 27-29. These proteins may be elevated in some people with breast cancer and are most useful for monitoring treatment response and checking for recurrence rather than for initial diagnosis.

Biomarker and genetic tests to diagnose breast cancer

Biomarker testing looks for specific features of the cancer cells to help guide treatment decisions. This is sometimes called molecular testing or tumor profiling. For breast cancer, important tests include:

• Hormone receptor (HR) testing. Tests whether the cancer cells have estrogen receptors (ER) and/or progesterone receptors (PR). HR-positive cancers can be treated with hormone therapy.
• HER2 testing. Checks for overexpression of the HER2 protein. HER2-positive cancers respond to HER2-targeted therapies.
• Ki-67. A marker of how quickly the cancer cells are dividing, which can help assess how aggressive the cancer is.
• Genomic tests (such as Oncotype DX, MammaPrint). These tests analyze the genes in a tumor to predict the likelihood of recurrence and help decide whether chemotherapy is needed, particularly for early-stage hormone receptor-positive, HER2-negative cancers.
• BRCA1/BRCA2 and other hereditary gene testing. May be recommended based on personal or family history to test for inherited gene mutations.
• PDL1 testing. Checks for expression of the PD-L1 protein, which may determine eligibility for immunotherapy (particularly in triple-negative breast cancer).
• Other biomarker tests. The field of biomarker testing is rapidly evolving. Your doctor may recommend additional tests based on your specific diagnosis, and new biomarkers are continually being studied. Ask your care team which tests were done on your tumor and what the results mean for your treatment.