Learn The BasicsThere are many different diagnostic methods and tests that can be used to diagnose breast cancer or determine a patient’s risk of developing it. The first step in the diagnosis of the disease is often a breast examination performed by the patient themselves or a doctor.
Other diagnostic tests include a mammogram, a breast ultrasound, a breast magnetic resonance imaging (MRI) and a breast biopsy.
There is also genetic testing that can help assess someone’s predisposition to developing breast cancer and biomarker testing that can help identify whether the cancer has spread, which treatment approach it is most likely to respond to and how well it is responding to a particular treatment.
Diagnostic tests
Breast examination
A self-examination or examination conducted by a doctor includes checking for something atypical in the breast. This could include changes in the skin or the nipple or the presence of any lumps in the breast, along the collarbone and in the armpit.
Mammogram
A mammogram uses low-dose X-rays to visualise breast tissue. It is usually used to screen for breast cancer.
During the procedure, a machine presses the breast between two surfaces to spread it out. The X-rays capture images of the breasts, which may show signs of breast cancer.
Breast ultrasound
A breast ultrasound provides images of the inside of the breast using high-frequency sound waves. It can show whether a breast lump is a cyst filled with fluid, which is usually non-cancerous, or a solid mass, which could be cancerous.
During the test, a handheld device called a transducer is run over the breast and surrounding tissues.
Breast MRI
A breast MRI is an imaging test that uses very strong magnets and radio waves to help doctors visualize the inside of the breast in great detail.
During a breast MRI, a patient is asked to lie face down on a padded table, which has a hollow space for the breasts to fit in. The table then slides inside the MRI machine.
A dye called a contrast agent may also be injected into the bloodstream to make the images easier to interpret.
A breast MRI may be done if signs of breast cancer have been seen in a biopsy to understand the extent of the cancer.
Breast biopsy
During a breast biopsy, a small sample of the breast tissue is taken out to be examined in the laboratory.
There are different types of biopsies depending on the location and the size of the affected area. These are needle biopsy, vacuum-assisted biopsy, fine needle aspiration, punch biopsy and wire-guided biopsy.
During a needle biopsy, a small cut is made in the skin of the breast and a hollow needle is used to take out a sample of the breast tissue.
During a vacuum-assisted biopsy, the needle is attached to a vacuum device to remove the sample.
Fine needle aspiration involves inserting a small needle into the breast and taking a sample of fluid and cells.
In a punch biopsy, a small cutting device is used to remove a sample of breast tissue just under the skin.
Finally, during a wire-guided biopsy, a thin wire is inserted into the breast to localize the exact area to remove.
Genetic testing
There are a number of genetic variants that increase someone’s risk of developing breast cancer. The most common of these are variants of the BRCA1 and BRCA2 genes with an estimated 1 in 400 people carrying a variant that may increase their risk.
A genetic test can identify which variant of the BRCA1 and BRCA2 genes a person has. The test involves taking a small blood sample from which DNA is extracted and its sequence analyzed in the laboratory.
Other genetic variants may increase the risk of breast cancer, and they can also be tested for. However, a genetic test is usually only conducted if someone has a family history of BC, as pathogenic variants are rare in the general population.
It’s important to understand that a genetic test cannot diagnose breast cancer.
Biomarker testing for breast cancer
Biomarker testing can help clarify how aggressive breast cancer might be, whether it has grown or spread, what treatment options are most likely to work and how well it is responding to treatment.
There are different types of biomarker tests. These include cancer antigen (CA) blood tests, circulating tumor cell or DNA tests, genomic tests for gene expression, immunohistochemistry tests, fluorescent in situ hybridization and next-generation sequencing.
CA blood tests
CA blood tests look for certain proteins in the blood, like CA 15-3, CA 27-29 and carcinoembryonic antigen (CEA), which may be elevated in the case of breast cancer.
Circulating tumor cell or DNA tests
Circulating tumor cell tests can identify whole cancer cells in the bloodstream originating from the tumor in the case of metastatic breast cancer. Similarly, circulating tumor DNA tests can identify fragments of genetic material in the bloodstream shed by cancer cells. This genetic material can help identify mutations in certain genes that can identify the best targeted therapy. It can also signal the presence of minimal residual disease.
Genomic tests
Genomic tests can identify which genes are “turned on” or “turned off” in a tumor tissue cell and determine the likelihood of breast cancer to recur, thereby guiding treatment decision-making.
Immunohistochemistry tests
Immunohistochemistry is done on a biopsy obtained during a breast biopsy and can identify biomarkers like hormone receptors, HER2 receptor and a protein called programmed cell death ligand 1 (PD-L1) and help with the best treatment choice.
Fluorescent in situ hybridization
Fluorescent in situ hybridization is also done on a biopsy sample and is usually used to determine whether the cancer is HER2-positive and whether the patient is eligible for HER2-targeted breast cancer therapies.
Next-generation sequencing
Finally, next-generation sequencing is a test to look for genetic changes or mutations in a tumor tissue. It can help identify hundreds of mutations in the genes of the tumor and the results can help decide on the best targeted therapy for a particular patient whose cancer has spread. The test is being increasingly used in cases of metastatic breast cancer.