HER2 Positive Breast Cancer Diagnosis

HER2-positive breast cancer is characterized by a high level of the human epidermal growth factor receptor 2 (HER2) protein. Normally, HER2 helps regulate healthy breast cell growth and repair by controlling cell division. When the HER2 gene is altered, however, it can overproduce the HER2 protein, driving rapid cancer cell growth.

Although the precise cause of the gene mutation that leads to HER2-positive breast cancer is not fully understood, scientists have determined that it is not inherited. Instead, this abnormal genetic change takes place sometime during the patient’s lifetime.

Approximately 20% of invasive breast cancers—including invasive ductal carcinoma (IDC), invasive lobular carcinoma (ILC), inflammatory breast cancer (IBC) and Paget’s disease of the nipple—are HER2-positive. The symptoms can be similar to those of other types of breast cancer, such as a breast lump, swelling or unusual changes in the breast skin or nipple.

Treatment often includes targeted therapy drugs that specifically block the HER2 protein, which may be combined with surgery, radiation therapy, chemotherapy or hormone therapy for enhanced effectiveness. HER2-targeted treatments, such as monoclonal antibody therapies and small molecule inhibitors, are continually advancing, significantly improving the outcome and quality of life for many patients with HER2-positive breast cancer.

How is HER2-positive breast cancer detected?

Like most types of breast cancer, HER2-positive breast cancer is usually detected through a combination of imaging scans, a biopsy and specialized laboratory testing. In many cases, a breast abnormality is first discovered by the patient during a self-examination or by a physician during a routine breast cancer screening. To determine whether cancer is present, the physician will typically order diagnostic imaging and a biopsy, which involves removing a small sample of suspicious tissue for microscopic examination by a pathologist. If the pathologist identifies cancerous cells in the sample, the tissue will be tested for HER2 status, which is an important consideration when planning breast cancer treatment.

Imaging tests used for diagnosing HER2-positive breast cancer

Several imaging techniques can be used to detect breast cancer and guide the diagnostic process. By providing detailed visuals of the breast tissue, these tests can help the physician identify suspicious changes that may require further evaluation with a biopsy.

The imaging tests most commonly used for diagnosing HER2-positive breast cancer include:

Mammogram

A mammogram is an X-ray of the breast. In many cases, it is the first imaging test used to diagnose breast cancer. The images may reveal abnormal masses, areas of dense tissue or small calcium deposits (calcifications) that may indicate cancer. If the findings are concerning, the physician may order follow-up imaging or a biopsy to confirm the diagnosis.

Breast ultrasound

Ultrasound uses high-frequency sound waves to create real-time images of soft tissue. This imaging technique can be particularly useful for determining whether a breast lump is a solid mass (possibly cancerous) or a fluid-filled cyst (likely benign). Additionally, because ultrasound can penetrate dense tissue more effectively than mammography, it can be an especially good imaging option for a patient with dense breasts. Often, ultrasound is used alongside mammography or to guide a biopsy procedure.

Breast magnetic resonance imaging (MRI)

MRI uses powerful magnets and radio waves to create detailed images of soft tissue. Due to its sensitivity, this imaging technique can detect subtle changes that may not be visible on a mammogram or ultrasound, making it especially valuable for evaluating patients with dense breast tissue and those at high risk for breast cancer. Breast MRI can also be used to help the physician assess the size of a tumor and determine whether it has spread within the breast or to nearby lymph nodes.

Breast tomosynthesis (3D mammography)

Breast tomosynthesis, also known as 3D mammography, involves multiple X-rays taken from different angles. The images are then compiled by a computer to create a three-dimensional picture of the breast. This imaging technique can improve the detection of small tumors and reduce the risk of a false positive result caused by overlapping breast tissue. 3D mammography can be particularly beneficial for patients with dense breast tissue.

Additional imaging for breast cancer staging

In some cases, after a diagnosis of HER2-positive breast cancer is confirmed, the physician may order additional imaging, such as computed tomography (CT), positron emission tomography (PET) and/or bone scans. While not used for initial breast cancer detection, these imaging techniques can help the physician determine whether the tumor has spread beyond the breast and nearby lymph nodes, which is essential for accurate staging and treatment planning.

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Procedures used for diagnosing HER2-positive breast cancer

If imaging suggests the possibility of breast cancer, the next step is usually a biopsy. This medical procedure involves obtaining a tissue sample that can be studied in detail to confirm the diagnosis. Biopsy procedures are often guided by imaging to help ensure the correct area of tissue is sampled. Once the specimen is collected, it will be sent to a laboratory for analysis.

Several biopsy procedures can be used to diagnose HER2-positive breast cancer, including:

Fine-needle aspiration (FNA)

FNA uses a very thin needle to collect a small sample of cells or fluid from suspicious tissue. The procedure is quick, minimally invasive and effective for evaluating certain breast abnormalities. However, because the sample size is limited, it may not provide sufficient information for a complete diagnosis. In some cases, FNA may need to be followed by additional testing.

Core needle biopsy

A core needle biopsy uses a large, hollow needle to remove small cylinders of suspicious tissue. The procedure is often performed with imaging guidance for heightened precision. Compared to FNA, core needle biopsy provides a larger sample, potentially allowing for a more accurate diagnosis. It is the most common type of biopsy performed when breast cancer is suspected.

Surgical biopsy

If the results of a needle biopsy are inconclusive or more tissue is needed for analysis, a surgical biopsy may be considered. This procedure involves removing a portion of the lump (incisional biopsy) or the entire lump (excisional biopsy) for evaluation by a pathologist.

Laboratory tests used for diagnosing HER2-positive breast cancer

If a biopsy confirms the presence of breast cancer, the next step is to determine whether the tumor is HER2-positive. This determination is critical, as it directly impacts the prognosis and can guide treatment planning.

Several laboratory tests can be used to determine the HER2 status of breast cancer, including:

Immunohistochemistry (IHC)

Usually the first lab test performed to identify HER2 status, IHC measures the amount of HER2 protein on the surface of breast cancer cells. After a special dye is applied to the tissue sample, a pathologist will examine it under a microscope. The dye will make the HER2 protein show up in color. Based on the amount of HER protein visible in the sample, the pathologist will assign a score ranging from 0 to 3+. A score of 0 or 1+ indicates the cancer is HER2-negative, a score of 2+ is considered equivocal (borderline) and a score of 3+ indicates the cancer is HER2-positive.

Fluorescence in situ hybridization (FISH)

FISH examines the HER2 gene to determine if extra copies are present. This lab test uses a fluorescent dye that binds to the HER2 gene inside breast cancer cells. When viewed under a special microscope, the dye will glow, allowing the pathologist to count the number of gene copies. If excessive copies are found, the cancer will be classified as HER2-positive. FISH is highly accurate and often used to confirm HER2 status when IHC results are borderline.

Other specialized tests

In some cases, other lab testing methods, such as chromogenic in situ hybridization (CISH) or silver in situ hybridization (SISH), may be used to determine HER2 status. These tests work similarly to FISH but utilize different techniques to visualize HER2 gene amplification.

Benefit from world-class care at Moffitt Cancer Center

An accurate diagnosis is the first and most important step in managing HER2-positive breast cancer. By using advanced imaging techniques, precise biopsy procedures and specialized laboratory tests, the physicians at Moffitt can identify the HER2 status of a breast tumor and develop a tailored treatment plan for the patient.

If you would like to learn more about the diagnostic process for HER2-positive breast cancer, you can request an appointment with a specialist in the HER2 Multidisciplinary Breast Clinic at Moffitt by calling 1-888-663-3488 or submitting a new patient registration form online. We do not require referrals.