How Breast Cancer is Diagnosed


Diagnosing breast cancer is a process. Most women who are diagnosed with breast cancer do not have any symptoms; their cancer is found during routine screening, like a mammogram. If you do have symptoms, or if your mammogram shows something in your breast, tell your doctor as soon as you can. Finding breast cancer when it is still small can give you more treatment options and make you more likely to respond well to them.

Your doctor might also want to remove more tumor tissue and send it for an OnctotypeTM test, a genomic test that gives information about the behavior of the cancerous tissue. If you've been screened and had abnormal mammogram results, your doctor should do a physical exam, find out your medical history, and tell you if you need further screening to make a diagnosis.

Diagnostic Mammograms

Sometimes, if you've received abnormal mammogram results, your doctor might need more images to get more information about a suspicious area. S/he may order a diagnostic mammogram, which takes more images than a regular screening mammogram. A radiologist will be present during the diagnostic mammogram to make sure the doctor gets all the images needed. If you originally had a 3D mammogram (also known as 3D tomosynthesis), which takes more pictures than a traditional mammogram, you may not need a diagnostic mammogram and instead have an ultrasound.


When a mammogram shows something suspicious, if no further examination is necessary, a doctor will perform a biopsy. A biopsy removes a few sample cells from the suspicious area on your breast. A kind of doctor called a pathologist looks at the biopsied cells under a microscope and decides if the cells are cancer or not. 80% of the time, the cells are not cancer—they are “benign.”

Finding breast cancer when it is still small can give you more treatment options and make you more likely to respond well to them. If the cells are “malignant,” or cancerous, your doctor might send the tissue sample out for more tests to learn what kinds of treatment your tumor cells might respond to.

Biomarker Tests

Nowadays, the doctors will check biomarkers, molecules that indicate normal or abnormal process taking place in your body, in the tissue taken out as the biopsy. This gives a good picture upfront about the behavior of the tumor, and will help determine the best treatment. Oncotype™ and Mammaprint™ are examples of tests on tumor tissue that can assist in predicting the behavior of the tumor and the prognosis by analyzing its genetic profile.

Some breast cancer cells depend on hormones like estrogen or progesterone to grow. All cells also have proteins that can be switched on or off; in some breast cancer cells, the HER2 protein is switched on, encouraging the tumor to keep growing. There are treatments specifically for these cells. You may be offered targeted therapy such as antiestrogen therapy or herceptin, lapatinib, etc. respectively.

Written by: Dr. Deborah Axelrod, NYU Langone. Last Updated: September 3, 2017 by Melissa Sakow.

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