Breast MRI is highly sensitive for the detection of breast cancer; its sensitivity is higher than that of mammography, and has been reported to range between 71%–100% ( ). However, the specificity of breast MRI is lower than that of mammography. Due to the expense and lower specificity of breast MRI, it is utilized for screening patients with an elevated lifetime risk of breast cancer, which the American Cancer Society describes as a >20% lifetime risk ( ). Breast MRI is also used for diagnostic indications including breast cancer staging and supplementary evaluation of a clinical symptom such as pathologic nipple discharge. Patients with suspicious MRI findings may be recalled for MRI-directed imaging with mammography or ultrasound to identify a potential correlate that can be targeted for biopsy with stereotactic or ultrasound guidance. However, if the suspicious MRI finding is occult on mammography and/or ultrasound, then an MRI-guided breast biopsy is recommended. Most commonly, the suspicious finding is reidentified at the time of MRI-guided breast biopsy, and the procedure is performed. Less commonly, the biopsy cannot be successfully performed. Potential reasons for an aborted MRI-guided biopsy include patient discomfort, a reaction to gadolinium-based contrast media, and lesion nonvisualization at the time of biopsy. Certainly, if a suspicious breast finding cannot be replicated and visualized, it cannot be confidently sampled. The question then remains for both the patient and the radiologist: what is the appropriate follow-up and management for patients in this scenario?
Prior authors have reported that between 8% and 13% of MRI-guided breast biopsies may be cancelled due to lesion nonvisualization on the day of biopsy ( ). In the Pinnamaneni et al. study, nonvisualization occurred in a slightly smaller percentage of 6% ( ). These authors’ findings suggest that lesion nonvisualization at biopsy occurs frequently enough that it is appropriate to discuss the possibility with the patient during the consent process in order to minimize patient anxiety or confusion. As proceduralists, it is important that we ensure technical factors are optimized prior to biopsy in order to contribute to a successful intervention. Pinnamaneni et al. highlight the practical aspects of MRI-guided breast biopsy that may contribute to lesion nonvisualization. The breast should be arranged in the coil so that the expected target area of the breast is compressed by the biopsy grid. Compression is applied to hold the breast steady for biopsy, but too much compression can cause patient discomfort and potentially impede blood flow and contrast contributing to nonvisualization of the finding. In 2014, El Khouli et al. reported that compression used for MRI-guided breast biopsy caused 12% of breast lesions to be significantly smaller in size than the initial MRI and 4% of lesions had complete loss of enhancement with biopsy-related compressions ( ). For this reason, Pinnamaneni et al. use light compression in initial biopsy positioning and decrease compression at 3 minutes post contrast if the lesion is not seen. Additional imaging for up to 10 minutes is performed to detect potential lesion enhancement with the release of compression ( ). Other institutions may consider employing the MRI-guided biopsy compression technique used by the authors to maximize visualization of suspicious findings.
Subsequent ipsilateral breast cancer has been reported in up to 10% of MRI-guided breast biopsy cancellations due to nonvisualized lesions ( ), a percentage that exceeds the widely accepted, BI-RADS-established >2% likelihood of malignancy threshold used to recommend or consider biopsy of a suspicious breast finding ( ). However, if a lesion is not visible to biopsy on any imaging modality, then it cannot be percutaneously biopsied or localized for surgical biopsy. In this instance, what is the appropriate follow-up to balance the likelihood of malignancy with appropriate recommendations in an era emphasizing value-based care? After all, other authors have reported that none of the patients with lesion nonvisualization at MRI-guided biopsy were diagnosed with ipsilateral breast cancer at subsequent follow-up ( ). The American College of Radiology’s Practice Parameter for the Performance of Magnetic Resonance Imaging-Guided Breast Interventional Procedures states that if a breast lesion recommended for biopsy is not seen at the time of the biopsy, then “short-interval follow-up MRI should be obtained to be certain the lesion is indeed absent” ( ). A 6-month interval follow-up breast MRI is often recommended for probably benign BI-RADS Category 3 findings; this 6-month interval for follow-up MRI could translate well to the clinical scenario of lesion nonvisualization at the time of attempted biopsy. The caveat to the short term follow-up MRI recommendation, however, is that many patients will not obtain the follow-up in the recommended time frame, typically due to lack of insurance coverage for the follow-up breast MRI. The Pinnamaneni et al. study has among the highest published patient volume with breast MRI follow-up after lesion nonvisualization; however, even among this study population, the median follow-up time is 21.9 months ( ), suggesting there is limited adherence to short-interval MRI follow-up recommendations for cases of lesion nonvisualization.
In their investigation, Pinnamaneni et al. found no demographic or imaging factors that were associated with lesion nonvisualization. Multiple factors including lesion type and enhancement kinetics, level of background parenchymal enhancement on the initial MRI, patient age, and menstrual status were examined; none of these were found to be associated with lesion nonvisualization. Only one of 54 (1.9%) patients were diagnosed with breast cancer at subsequent follow-up ( ). The breast cancer in this study was a case of ductal carcinoma in situ which was diagnosed at the follow-up MRI of 6 months. Other authors have reported both invasive and noninvasive disease on follow-up of lesions not visualized at time of MRI-guided biopsy ( ).
When nonvisualization of a suspicious lesion happens at the time of MRI-guided breast biopsy, I have anecdotally ascribed the cases to physiologic, hormonal background enhancement. Interestingly, this assumption was not necessarily supported by Pinnamaneni’s data; they found that 30% of patients with lesion nonvisualization were postmenopausal patients ( ), who would not necessarily have much hormonal variation in background enhancement. In these postmenopausal patients, lesion nonvisualization may be related to other factors. Physiologic related enhancement often manifests as nonmass enhancement and/or foci. But Pinnamaneni et al. found that masses also were not visualized at the time of biopsy, suggesting that factors other than background enhancement variation contribute to nonvisualization of lesions at biopsy. Another factor that may contribute to lesion nonvisualization is the suspicious finding potentially being masked by increased background parenchymal enhancement. When possible, breast MRI may be performed during the second week of the menstrual cycle in premenopausal women in order to minimize physiologic background enhancement ( ). However, most women are not biopsied during this specific cyclic window for practicality purposes and to reduce patient anxiety by offering biopsy in a timely fashion. In fact, in this study 86% of premenopausal patients were not biopsied during the same cyclic time point as the initial breast MRI ( ), confirming that cyclic timing of the MRI-guided biopsy is not practical for routine clinical practice.
The causes of lesion nonvisualization at the time of MRI-guided breast biopsy are not definitively known and may vary with patient; factors may include compression and menstrual cycle timing. There are no specific imaging features or demographic factors associated with lesion nonvisualization or subsequent breast cancer. Pinnamaneni et al. identify best practices that may be utilized at other institutions to optimize lesion visualization at the time of MRI-guided breast biopsy. Although infrequent, ipsilateral malignancy can subsequently be diagnosed when there is lesion nonvisualization at MRI-guided breast biopsy. For this reason, a recommendation for breast MRI follow-up is warranted.
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