Doctors use specialized tests to analyze your cancer cells and gather information to determine your breast cancer type.
Once you've been diagnosed with breast cancer, your doctor will review your pathology report and the results of any imaging tests to understand the specifics of your tumor.
Using a tissue sample from your breast biopsy or using your tumor if you've already undergone surgery, your medical team determines your breast cancer type. This information helps your doctor decide which treatment options are most appropriate for you.
Here's what's used to determine your breast cancer type.
The type of tissue where your breast cancer arises determines how the cancer behaves and what treatments are most effective. Parts of the breast where cancer begins include:
Milk ducts. Ductal carcinoma is the most common type of breast cancer. This type of cancer forms in the lining of a milk duct within your breast. The ducts carry breast milk from the lobules, where it's made, to the nipple.
Ductal carcinoma can remain within the ducts as a noninvasive cancer (ductal carcinoma in situ), or it can break out of the ducts (invasive ductal carcinoma).
Each breast contains 15 to 20 lobes of glandular tissue, arranged like the petals of a daisy. The lobes are further divided into smaller lobules that produce milk for breastfeeding. Small tubes (ducts) conduct the milk to a reservoir that lies just beneath your nipple.
When a sample of your breast cancer is examined under a microscope, here's what the pathologist looks for:
Some breast cancers are sensitive to your body's naturally occurring female hormones — estrogen and progesterone. The breast cancer cells have receptors on the outside of their walls that can catch specific hormones that circulate through your body.
Knowing your breast cancer is sensitive to hormones gives your doctor a better idea of how best to treat the cancer or prevent cancer from recurring.
Hormone status of breast cancers includes:
Doctors are just beginning to understand how the individual DNA changes within cancer cells might one day be used to determine treatment options. By analyzing the genes of cancer cells, doctors hope to find ways to target specific aspects of the cancer cells to kill them.
A sample of your tumor tissue from a biopsy procedure may be tested in a laboratory to look for:
Other tumor markers. Researchers are studying ways to interpret the genetic makeup of tumor cells. Doctors hope this information can be used to predict which cancers will spread and which may need aggressive treatments. That way, women with relatively low-risk breast cancers may avoid aggressive treatments.
Tests that analyze the genetic makeup of breast cancers are available but aren't recommended in all situations. Ask your doctor whether this type of test might be helpful in your case.
Doctors are increasingly using genetic information about breast cancer cells to categorize breast cancers. These groups help guide decisions about which treatments are best. Breast cancer groups include:
Understanding more about the chemical and genetic makeup of your cancer may help doctors choose the most effective treatment for your specific cancer.