How Is Metastatic Breast Cancer Diagnosed?
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Medically reviewed by Marla Anderson, MD
Metastatic breast cancer (MBC) is an advanced form of breast cancer that occurs when cancer cells spread beyond the breast and nearby lymph nodes to other parts of the body—such as the bones, lungs, liver, or brain. Healthcare providers use a series of blood tests, imaging scans, and biopsies to determine if you have MBC.
Some people receive their first breast cancer diagnosis after it has already spread to other body areas. This is known as "de novo" metastatic breast cancer. In most cases, an MBC diagnosis comes after treatment for early-stage breast cancer confined to the breast.
If breast cancer cells remain in the body after treatment and enter the bloodstream or lymphatic fluid, they can travel to different parts of the body and form new tumors. This is known as a "metastatic recurrence."
An oncologist (a medical doctor specializing in diagnosing and treating cancers) may order several tests to check for the presence of cancer cells in your body. They will likely order tests for MBC if you are in the early stages of breast cancer, develop symptoms of MBC like headache, bone pain, or shortness of breath, receive abnormal results on a recent mammogram, or have a biopsy result that indicates you're in a later stage of breast cancer.
Blood Tests
Blood tests provide information about your overall health and clues about where cancer has spread (metastasized). Your healthcare team may order one or more of the following exams:
Complete blood count (CBC): Measures the levels of different types of blood cells, including red and white blood cells, platelets, and hemoglobin levels. CBC results can help identify issues like anemia (low red blood cell count), compromised immune function (low white blood cells), and thrombocytopenia (low platelet count).
Serum chemistry panel: Assesses the presence of various minerals (e.g., potassium, calcium) and enzymes in the blood to evaluate liver and kidney function. Abnormal levels of certain minerals and enzymes can sometimes signal where breast cancer cells have spread. For example, abnormal calcium levels may mean breast cancer has spread to the bones.
Tumor marker tests: Check the levels of specific proteins (antigens) that circulate in the blood of people with metastatic breast cancer.
Circulating tumor cells (CTCs): Detects for the presence of cancer cells circulating in the bloodstream. CTCs in the bloodstream show that cancer cells have broken away from the site of the original tumor (in the breast) and are traveling through the body.
Imaging Scans
Imaging scans provide detailed images of your body's internal structures. They help oncologists identify suspicious tumors or abnormalities that indicate that breast cancer has spread to other parts of your body. Common imaging tests for MBC include:
Chest X-ray: Takes pictures of your chest to look for cancer that has spread from the breast to the lungs—a common site for breast cancer metastasis (spread)
Bone scan: Detects if cancer has spread to the bone, which is more common in advanced breast cancer stages. This test involves injecting a small amount of radioactive material (known as a tracer) into a vein and using a special camera to scan your bones. The tracer collects in injured areas of the bone (e.g., in tumors), so cancerous lesions appear darker on the scan, whereas healthy bone appears lighter.
Computed tomography (CT) scan: Uses X-rays to take pictures from various angles and create detailed cross-sectional images of your body. CT scans are valuable for examining the lungs, liver, bones, and lymph nodes for abnormalities and for measuring tumors if they're detected.
Magnetic resonance imaging (MRI) scan: Utilizes strong magnetic fields and radio waves to create detailed images of organs and tissues. A special dye (known as a contrast medium) gets injected into your veins before the test to help create a clearer picture. An MRI helps evaluate specific areas of concern and measure the size of tumors.
Positron emission tomography (PET) scan: Reveals the location of metastatic tumors in the body's tissues and organs. This test involves injecting a radioactive sugar substance into your bloodstream, which cells use for energy. Cancer cells use more energy than healthy cells and absorb more radioactive sugars, which makes them appear brighter on the scan.
Biopsy
Imaging and blood tests are essential tools in the metastatic breast cancer diagnostic process, but a biopsy is the only way to provide a definitive diagnosis. A biopsy involves removing a small tissue sample from a part of your body for microscopic examination by a pathologist (a doctor who specializes in diagnosing diseases). The pathologist examines the suspicious tissue to identify and confirm the presence of cancer cells.
The specific biopsy procedure for diagnosing metastatic breast cancer depends on the location of the suspected metastasis. Common types of biopsies include:
Needle biopsy: Removes a small tissue sample by inserting a thin needle into the area with a suspected tumor. Healthcare providers use imaging scans, such as ultrasounds and CT scans, to guide the needle to the precise location.
Laparoscopic or thoracoscopic biopsy: Makes small incisions (cuts) in the abdomen and inserts a laparoscope (a small, flexible tube equipped with a tiny camera and light) to view suspicious areas and take out small tissue samples. A laparoscopic biopsy obtains tissue samples from the abdomen and pelvis, while a thoracoscopic biopsy takes tissue samples from the chest.
Surgical biopsy: Involves making an incision in the skin to remove a larger tissue sample or tumor for analysis. The type of surgical procedure depends on the location of the suspected tumor.
A biopsy confirms a diagnosis of metastatic breast cancer and provides valuable information about the subtype of breast cancer by checking for specific tumor characteristics, such as:
Estrogen and progesterone receptors: Testing a tumor's hormone receptor status determines whether breast cancer cells have receptors (proteins) that attach to estrogen and progesterone. These hormones can fuel cancer growth in breast cancer cells with these receptors. Knowing the hormone receptor status of breast cancer cells helps determine whether treatment that controls or stops hormones from acting on breast cancer cells is necessary.
HER2 status: HER2 is a protein that promotes the growth of breast cancer cells. Breast cancer cells with high levels of HER2 tend to grow and spread more quickly than other breast cancer cells. If metastatic breast cancer is HER2 positive, it is more likely to respond to drugs that target the HER2 protein.
Your healthcare provider may also run additional tests on the tissue sample to look for biomarkers in cancer cells. Biomarker tumor testing analyzes the genes within cancer cells to identify mutations (changes) that might influence the cancer's response to treatments.
Genetic Testing
If you have a family history of breast cancer, your healthcare provider may recommend genetic testing. Genetic testing identifies whether you have inherited gene mutations (changes) that may contribute to the development of MBC. The test involves taking a small blood, saliva, or cheek swab sample and sending it to the lab for analysis.
If your results are positive, healthcare providers can determine what is causing cancer to grow and use the information to guide treatment decisions. This information is also helpful for at-risk family members who may opt for more frequent breast cancer screenings.
A Quick Review
Metastatic breast cancer is the most advanced form of breast cancer. Having MBC means that breast cancer cells have spread to other areas of the body, such as the brain, bones, liver, or lungs.
No single test can diagnose metastatic breast cancer, so oncologists use a combination of blood tests, imaging scans, and biopsy (tissue sample) results to confirm the diagnosis and determine where in the body the cancer has spread.
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