Breast ultrasound without “false” steps

Kathy J. Schilling, MD - Print  | 

At a high-volume breast imaging center, the addition of elastography helps avert both false positives and false negatives.

Ultrasound screening enables physicians to find masses that are not detected on mammography as well as gain more information on mammographically identified lesions with targeted imaging. Use of the modality has increased as physicians have learned more about the challenges of mammography in dense breasts.

At our facility, we performed breast ultrasound on more than 10,000 patients in the past year, nearly half of whom were referred for supplemental screening due to dense breasts. The number will be even higher in 2017. More and more physicians understand that mammographic sensitivity in dense tissue is very low due to the masking phenomenon. Additionally we see patients who require a diagnostic ultrasound after a suspicious physical finding, mammogram or MRI.

Elastography and Tissue Stiffness
With traditional ultrasound, high sensitivity has resulted in occasional false positive results disproven by biopsy, which in turn has had a negative impact on some physicians’ desire to use ultrasound for breast screening. Elastography technology changes this dynamic.

The ultrasound system (Aixplorer, SuperSonic Imagine) uses a technology called real-time ShearWave Elastography (SWE), which displays a color-coded map with analysis of tissue stiffness. This information allows physicians to determine with confidence if a lesion is likely to be benign or malignant based on stiffness compared to background breast tissue when used in conjunction with morphologic analysis. Malignant lesions typically are stiff, whereas benign lesions tend to be soft. By combining tissue stiffness data with lesion morphology, SWE improves the specificity of ultrasound, reducing false positives and false negatives.

My colleagues and I have been using SWE for eight years, and we would not work without it now. When initially evaluating SWE, we did an assessment of all patients who were to have an ultrasound biopsy. By performing SWE prior to biopsy, we were able to rapidly learn the technique of image acquisition as well as the expected appearance of benign and malignant lesions. Through the immediate feedback on lesion pathology, my colleagues and I gained a high level of confidence in SWE and saw its potential to impact patient outcomes

Since using our current ultrasound system equipped with shear wave elastography, we have reduced our benign biopsy rate by 50%. I believe the primary reason is the information offered by SWE. In addition to improving outcomes, it improves the efficiency of our department. It enables us to say, with confidence, “This is not cancer. We do not need a biopsy.”

The two cases that follow illustrate how SWE has helped us avoid both false positive and potentially life threatening false negatives.

No False Positive, No Biopsy

A 47-year-old patient was referred for ultrasound biopsy because a very small, rounded solid mass located on one of the patient’s breast implants was found. Using SWE to evaluate the tissue stiffness, the mass was soft and likely benign. A biopsy was performed and a fibroadenoma was subsequently diagnosed. The accurate SWE findings could have been used to avoid the biopsy.

The biopsy was somewhat risky because the mass’ proximity to the implant made rupture a concern. Utilizing SWE, this patient could have avoided biopsy and the accompanying physical and emotional stress. We have been able to change BIRADS 4A lesions to BIRADS 3 or 2 through the use of this new technology.

Spotting a False Negative

Although a rapidly growing cancer is generally associated with irregular margins, it can have smooth rounded pushing margins, making it easy to mistake for benign lesion. In these cases, SWE shows tissue in and around the lesion to be stiff, requiring biopsy.

For example, a 67-year-old patient was having ultrasound for breast density screening. Imaging showed that the patient had a benign-appearing circumscribed solid mass. The SWE analysis was mildly suspicious, with stiff tissue around the mass. A biopsy was performed. Pathology returned benign but was considered discordant with the SWE findings. A second biopsy identified malignancy. The patient was found to have a low-grade ductal carcinoma in situ.

By making the decision to perform a second biopsy based on the elastography finding, a false negative diagnosis was avoided. Without SWE, cancer diagnosis may have been delayed, presumably until it was detected at a later stage.

Adding the benefits of SWE to highly sensitive ultrasound imaging, we gain the accuracy and confidence to avert false positives and false negatives for patients in our practice. I continue to be surprised that more practices do not use shear wave elastography. It has been around for some time, and you could not take it away from radiologists in my department who rely on it heavily for more accurate breast imaging.

Kathy J. Schilling, MD, is Medical Director of Lynn Women's Health and Wellness Institute, Boca Raton Regional Hospital, Boca Raton, Fl.

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