Breast MRI scan with a highlighted lesion, overlaid with an ultrasound wave pattern.

MRI-Guided Breast Biopsies: Are Second-Look Ultrasounds Really Necessary?

Lena Voss in Health & Wellness December 2025 • 4 min read.

"New research clarifies the role of second-look ultrasounds in breast cancer detection, helping to streamline the diagnostic process."

Breast Magnetic Resonance Imaging (MRI) is a powerful tool for detecting suspicious lesions, particularly those that are not apparent through traditional mammography or clinical examination. When these lesions are found, a biopsy is often necessary to determine whether they are cancerous. MRI-guided biopsies have become increasingly common, offering a precise way to sample these potentially problematic areas.

However, before resorting to an MRI-guided biopsy, doctors often use a targeted second-look ultrasound (SLUS) to see if the lesion can be visualized and biopsied using ultrasound guidance, a less expensive and more accessible technique. The question then becomes: what happens when the SLUS comes back negative – meaning the lesion isn't visible on ultrasound? Does this negative result influence the outcome of the subsequent MRI-guided biopsy?

A new study, published in the Canadian Association of Radiologists Journal, sheds light on this issue. Researchers investigated the outcomes of MRI-guided breast biopsies in women who had previously undergone a negative targeted SLUS. Their findings could help refine clinical practice, potentially reducing unnecessary procedures and improving the efficiency of breast cancer diagnosis.

Does a Negative Ultrasound Impact MRI Biopsy Results?

Breast MRI scan with a highlighted lesion, overlaid with an ultrasound wave pattern.

Researchers at the McGill University Health Centre and other institutions conducted a retrospective study involving 158 women with breast lesions detected by MRI. All patients were scheduled for an MRI-guided biopsy. The study looked at several factors, including whether patients had undergone a targeted SLUS prior to the MRI-guided biopsy, the characteristics of the lesions seen on MRI, and the final pathology results.

Here’s a breakdown of the key aspects of the study:

Study Population: 158 women with MRI-detected breast lesions.
SLUS Prior to MRI: 63% of the women (98 out of 155 lesions biopsied) had a targeted SLUS before the MRI-guided biopsy.
Malignancy Rate: 15% of the biopsied lesions were found to be malignant.
Benign vs. High-Risk: 68% of lesions were benign, and 17% were classified as high-risk.
Key Finding: A negative SLUS did not influence the pathology outcome of lesions biopsied under MRI guidance.

The study found that a prior negative SLUS did not significantly alter the likelihood of malignancy or high-risk findings in the subsequent MRI-guided biopsy. In other words, if a suspicious lesion is seen on MRI but not on ultrasound, the MRI-guided biopsy results remain reliable and are not negatively impacted by the previous ultrasound findings.

What This Means for Breast Cancer Detection

This research provides valuable insights for radiologists and other healthcare professionals involved in breast cancer diagnosis. The key takeaway is that a negative second-look ultrasound should not deter or undermine the importance of proceeding with an MRI-guided biopsy when a suspicious lesion is identified on MRI.

These finding helps to reduce unnecessary procedures. By clarifying the role of SLUS in the diagnostic pathway, this study can contribute to more efficient and cost-effective breast cancer detection strategies.

While this study offers important clarity, further research could explore factors influencing the detection rate of SLUS and refine the selection criteria for MRI-guided biopsies to optimize diagnostic accuracy and patient outcomes.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/j.carj.2017.03.003, Alternate LINK

Title: The Positive Outcome Of Mri-Guided Vacuum Assisted Core Needle Breast Biopsies Is Not Influenced By A Prior Negative Targeted Second-Look Ultrasound

Subject: Radiology, Nuclear Medicine and imaging

Journal: Canadian Association of Radiologists Journal

Publisher: SAGE Publications

Authors: Romuald Ferré, Shaza Alsharif, Ann Aldis, Benoît Mesurolle

Published: 2017-11-01

Everything You Need To Know

What is Breast MRI, and why is it used?

Breast Magnetic Resonance Imaging (MRI) is a specialized imaging technique particularly useful for detecting suspicious breast lesions that are not visible through traditional methods like mammography. These lesions then often require a biopsy to determine if they are cancerous. The use of MRI-guided biopsies allows for precise sampling of these areas, which is essential for accurate diagnosis. In contrast to this, clinical examination relies on a physical assessment by a healthcare professional.

What is a Second-Look Ultrasound (SLUS), and what is its purpose?

Second-look ultrasounds (SLUS) are a type of targeted ultrasound used to visualize lesions identified on Breast MRI. The goal is to determine if the lesion can be biopsied using ultrasound, which is a more accessible and less expensive technique than MRI-guided biopsy. If the SLUS is negative, it means the lesion isn't visible on ultrasound, and the next step is often the MRI-guided biopsy. It is a crucial step in the diagnostic process because it helps clinicians decide the most effective and least invasive approach for obtaining a tissue sample.

Why are MRI-guided biopsies important?

MRI-guided biopsies are important because they offer a highly precise method for sampling suspicious breast lesions detected by Breast MRI. This precision is essential, particularly when lesions are difficult to locate through other methods. The implications of proceeding with an MRI-guided biopsy, even after a negative Second-Look Ultrasound (SLUS), include the potential for early and accurate cancer detection. The study shows that the negative SLUS does not undermine the reliability of the MRI-guided biopsy.

What were the key findings of the study regarding Second-Look Ultrasounds (SLUS) and MRI-guided biopsies?

The study involved 158 women with breast lesions identified through Breast Magnetic Resonance Imaging (MRI). Before the MRI-guided biopsy, 63% of these women underwent a targeted Second-Look Ultrasound (SLUS). The researchers examined whether the results of the SLUS influenced the outcomes of the subsequent MRI-guided biopsy. The study found that the prior negative SLUS did not significantly alter the likelihood of finding malignancy or high-risk findings in the subsequent MRI-guided biopsy.

What is the significance of a negative Second-Look Ultrasound (SLUS) result in the context of MRI-guided biopsies?

A negative Second-Look Ultrasound (SLUS) result should not prevent or reduce the importance of performing an MRI-guided biopsy when a suspicious lesion is identified on Breast Magnetic Resonance Imaging (MRI). This research provides valuable insights for healthcare professionals involved in breast cancer diagnosis by clarifying the role of SLUS and MRI-guided biopsies. It helps streamline the diagnostic process, potentially reducing unnecessary procedures and improving patient care. This allows for the use of the most effective and precise diagnostic tools available to the patient without delay based on a negative but separate test.