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Breast Pathology

Accurate Results

Ensuring the accuracy of your pathology results is of utmost importance. Knowing the exact type of breast cancer and the specifics of its prognostic factors is critical to creating a treatment plan that will provide you with the best opportunity for defeating this disease.

Our team of breast specialists includes pathology faculty members who specialize in breast cancer and have extensive experience evaluating and accurately classifying breast tissue specimens. Our pathologists are so trusted that it’s common for women to bring their slides from another facility to us for a second opinion. On occasion we discover abnormalities, including breast cancer, which may have been previously overlooked.

Learn more about breast pathology at Johns Hopkins Medicine.

Common Breast Cancer Pathology Terms

The following terms were developed by pathologists to describe the types and kinds of breast cancers. These descriptions help the breast surgical oncologist, medical oncologist and radiation oncologist design an individualized treatment plan for each patient.

  • HR-positive/negative (hormone receptor status) – Most breast cancers make a protein called estrogen receptor.  Breast cancers that make this protein can usually be treated with anti-hormonal medications.   Breast cancers that make a lot of estrogen receptor and also a lot of a related protein, called progesterone receptor, usually have a favorable prognosis. Anti-hormonal therapy is often part of the treatment of these cancers. It can greatly aid in preventing recurrence of the disease and can also help control breast cancer that has spread to other organs.
  • HER-2/neu receptor – The human epidermal growth factor receptor 2 (HER-2/neu) is a protein that can drive breast cancer cells to divide.  About 15% of breast cancers are positive for this protein. These breast cancers have a higher recurrence risk than many other breast cancers, but they are effectively treated with anti-HER2 medications such as trastuzumab or pertuzumab.   

There are two different tests used to measure HER2 in breast cancer cells. The first uses immununohistochemistry (IHC) to measure how much HER2 protein is on the surface of the cells. An IHC score of 0 or 1+ means there is no excess protein, 3+  means there is excess HER2 protein (this is called “positive”), and 2+ is equivocal.   The equivocal IHC test is followed up with a test called fluorescence in situ hybridization (FISH) which measures the number of copies of the HER2 gene in each cell.  If there are too many copies of the HER2 gene the test is called “positive”.

There is also something commonly referred to as triple negative breast cancer. This means that the cells do not make estrogen receptor, progesterone receptor or the HER2 protein. 

  • Grade – This is a measure of how the breast cancer cells look under the microscope Grade 1 cells look almost like normal breast cells, while grade 3 cells look very disorganized (i.e. more aggressive).  Grade 2 cells are somewhere in between.  Proliferation:  This test, sometimes called a Ki67 test, measures the percentage of tumor cells that were actively making copies of themselves at the time of the biopsy. For younger women who are still having menstrual cycles a value < 15% is considered good prognosis.  For women who no longer have menstrual cycles, < 10% is good.

Breast cancers are as different from one another as the women who develop them.  At one end of the spectrum are slow growing breast cancers that are unlikely to ever cause harm, and at the other end are aggressive breast cancers that are difficult to treat.  Most breast cancers are somewhere in between.  The oncologist looks at factors like tumor size, grade and lymph node status as well as the results of the ER, PR, HER2 and Ki67 marker tests to get a sense as to how an individual cancer is likely to behave. 

  • Benign breast diseases – Around 80 percent of suspicious masses found on mammograms or breast exams are benign, meaning they are not cancerous and pose no health risk. If our pathologists examine your slides and find no evidence of cancer, the surgeon will determine if the benign tumor, usually a fibroadenoma, needs to be removed. If they are large, increasing in size or causing pain, the surgeon will remove them.
  • Malignant tumors – Malignant tumors are cancerous tumors and need to be treated as such. Our pathologists will carefully evaluate all biopsies and slides to give the treating surgical, medical and radiation oncologists information about the size, type and prognostic factors of the tumor. Armed with these precise facts, our team can create an individualized treatment plan that targets the exact nature of your breast cancer.

Frequently Asked Questions about Pathology Results

Many patients have posted questions related to their pathology results and have received responses from our expert pathologists. Please visit our Ask an Expert section to ask your own question and review similar questions.

Navigate our Pathology FAQs and Images

  1. Benign Breast FAQ
  2. Benign Diseases - Atlas of Images
  3. Atypical Hyperplasia
  4. Breast Cancer In-Situ
  5. Breast Cancer
  6. Malignant Tumors - Atlas of Images
  7. Ask an Expert - Understanding Pathology Results