Introduction: Who Should Undergo Diagnostics
If you or your doctor notice any changes in your breast, such as a lump, unusual pain, skin changes, or nipple discharge, diagnostic testing is essential. These tests help determine whether breast cancer is present and, if so, what type it is. Not every breast concern means cancer, but proper diagnostics provide the clarity needed to move forward with confidence and appropriate care.[1]
When breast cancer is suspected, doctors need to know more than just whether cancer is present. They must understand the cancer’s specific characteristics to plan the most effective treatment. This is especially important for hormone receptor positive breast cancer, which makes up about 70 to 80 percent of all breast cancer cases in women. Men can also develop this type of cancer, with approximately 90 percent of breast cancers in men being estrogen receptor positive (ER-positive).[2][3]
Anyone diagnosed with breast cancer should undergo testing to determine their hormone receptor status, which means checking whether the cancer cells contain proteins called hormone receptors. These receptors can bind to hormones like estrogen and progesterone, which may fuel the cancer’s growth. Knowing your hormone receptor status helps doctors choose treatments that block these hormones from feeding the cancer.[4]
Most women with breast cancer will undergo diagnostic testing after noticing symptoms themselves or after an abnormal screening mammogram. The process typically starts with imaging, followed by tissue sampling to examine cells under a microscope. These steps help distinguish breast cancer from other breast conditions and identify its unique features.[1]
Diagnostic Methods
Understanding Hormone Receptors
Breast cells naturally contain special proteins called hormone receptors. These receptors receive messages from hormones traveling through your body and tell the cells what to do. In healthy breast tissue, this is a normal process. However, when breast cancer develops, some cancer cells also have these receptors. The two main types are estrogen receptors and progesterone receptors.[1]
When estrogen or progesterone hormones attach to these receptors on cancer cells, they can signal the cancer to grow and multiply. This is why identifying whether cancer cells have hormone receptors is so crucial—it reveals whether hormones are helping the cancer grow, which directly affects treatment choices.[4]
Biopsy: The First Step
To determine whether breast cancer is hormone receptor positive, doctors must examine actual cancer tissue. This requires a biopsy, which means removing a small sample of tissue from the suspicious area. The biopsy can be performed in different ways, but all aim to collect cells that can be studied in detail.[1]
The biopsy procedure might be done using a needle inserted into the breast to remove tissue, or it might involve surgical removal of the lump or suspicious area. Your doctor will recommend the best approach based on the location and size of the concerning area. The tissue sample is then sent to a laboratory for detailed analysis.[3]
Hormone Receptor Testing
All invasive breast cancers—meaning cancers that have the potential to spread to other parts of the body—should be tested for both estrogen and progesterone receptors. This testing is performed on the tissue obtained from the biopsy or after surgery to remove the cancer.[1]
The laboratory test used is called immunohistochemistry (IHC), which measures how many hormone receptors are present on the cancer cells. The results are reported as a percentage—higher percentages mean the tumor is more responsive to hormones. If the tumor cells contain estrogen receptors, the cancer is called estrogen receptor positive (ER-positive). If they contain progesterone receptors, it’s called progesterone receptor positive (PR-positive).[3][2]
Your cancer might be positive for one or both hormone receptors. This can be written in different ways, such as ER+/PR+, ER+/PR-, or ER-/PR+. Most ER-positive breast cancers are also PR-positive. Approximately 67 to 80 percent of breast cancers in women are ER-positive, and about 65 percent are positive for both estrogen and progesterone receptors.[2][7]
Interpreting Test Results
When the pathology report comes back, it will clearly state whether your breast cancer is hormone receptor positive or negative. If the report shows that the tumor has estrogen receptors, progesterone receptors, or both, this means the cancer is hormone receptor positive (HR-positive) or hormone sensitive. These cancers respond to treatments that block hormones or reduce hormone levels in the body.[2]
If the cancer lacks estrogen receptors, it’s called ER-negative. If it lacks both estrogen and progesterone receptors, it may be called HR-negative. These cancers grow without the help of hormones and don’t respond to hormone-blocking treatments. About 20 to 25 percent of breast cancers are ER-negative.[2]
There’s also a possibility of triple-positive breast cancer, which means the cancer is ER-positive, PR-positive, and also positive for another protein called HER2. Each combination responds differently to treatments, which is why accurate testing is so important.[3]
Additional Testing
Beyond hormone receptor testing, doctors typically order additional tests to get a complete picture of the cancer. These might include testing for HER2 status, determining the cancer’s grade (how abnormal the cells look), and establishing the stage (how far the cancer has spread). All this information together helps your medical team develop the most effective treatment plan.[4]
Hormone receptor positive breast cancers tend to grow more slowly than hormone receptor negative cancers. This is one reason why knowing your HR status matters—it provides insight into how the cancer might behave and what treatments are likely to work best.[3]
Diagnostics for Clinical Trial Qualification
Clinical trials are research studies that test new treatments or combinations of treatments. If you’re considering joining a clinical trial for hormone receptor positive breast cancer, you’ll need to undergo specific diagnostic tests to determine whether you’re eligible. These tests ensure that participants meet the study’s requirements and that the treatment being studied is appropriate for their specific type of cancer.[5]
Most clinical trials for HR-positive breast cancer require confirmation of your hormone receptor status through laboratory testing. This means you’ll need documentation from a biopsy showing that your cancer is indeed estrogen receptor positive, progesterone receptor positive, or both. The trial may have specific requirements about the percentage of cells that must test positive.[3]
Additionally, trials often require testing for HER2 status because some studies focus specifically on cancers that are HR-positive but HER2-negative, while others include or exclude HER2-positive cancers. Your complete biomarker profile—including hormone receptors and HER2—helps researchers match you with the most appropriate trial.[5]
Clinical trials may also require imaging tests such as CT scans, MRI scans, or bone scans to determine the extent of cancer spread. Blood tests to check liver and kidney function, blood cell counts, and overall health are typically needed as well. These baseline measurements help researchers track how well the treatment is working and monitor for any side effects during the trial.[2]
Some trials investigating new hormone therapies may require additional specialized tests, such as genetic testing or molecular profiling of the tumor. These tests can identify specific mutations or characteristics that might predict how well the experimental treatment will work. The trial team will explain exactly what tests are needed and why they’re important for the research.[5]
Before enrolling in a clinical trial, you’ll receive detailed information about what the study involves, including all required tests and procedures. This process, called informed consent, ensures you understand what to expect and can make an educated decision about participation. The diagnostic tests performed for trial qualification also provide valuable information about your cancer that can guide treatment decisions even if you choose not to participate.[2]
