BI-RADS 3: Current and Future Use of Probably Benign

Abstract

Purpose of review: Probably benign (BI-RADS 3) causes confusion for interpreting physicians and referring physicians and can induce significant patient anxiety. The best uses and evidence for using this assessment category in mammography, breast ultrasound, and breast MRI will be reviewed; the reader will have a better understanding of how and when to use BI-RADS 3.

Recent findings: Interobserver variability in the use of BI-RADS 3 has been documented. The 5th edition of the BI-RADS atlas details the appropriate use of BI-RADS 3 for diagnostic mammography, ultrasound, and MRI, and discourages its use in screening mammography. Data mining, elastography, and diffusion weighted MRI have been evaluated to maximize the accuracy of BI-RADS 3.

Summary: BI-RADS 3 is an evolving assessment category. When used properly, it reduces the number of benign biopsies while allowing the breast imager to maintain a high sensitivity for the detection of early stage breast cancer.

Keywords: BI-RADS 3; Breast cancer screening; Breast imaging reporting and data system; Breast ultrasound; MRI; Mammography; Probably benign.

Fig. 1

Mammographic appearance of solitary group of round or punctate calcifications, which are appropriate for BI-RADS 3

Fig. 2

Non-calcified circumscribed oval mass on mammography

Fig. 3

Focal asymmetry without calcifications or architectural distortion

Fig. 4

Calcifications in a patient with a history of trauma, consistent with fat necrosis

Fig. 5

Focal asymmetry with post-surgical architectural distortion seen on mammography and ultrasound in a patient with prior breast surgery. This was initially assessed as BI-RADS 3 but subsequent follow-up mammograms demonstrate long-term stability

Fig. 6

a Typical appearance of a BI-RADS 3 oval mass, with circumscribed margins and parallel orientation. b Anechoic cyst with thin internal septations, assessed as BI-RADS 3. c Clusters of anechoic microcysts, assessed as BI-RADS 3

Fig. 7

Weeks 0, 6, and 11: suspected fat necrosis in a patient with known breast trauma. Short interval follow-up demonstrates decreasing size of the mass confirming the diagnosis

Fig. 8

Interval growth of a BI-RADS 3 mass. This solid oval mass on ultrasound was assessed as BI-RADS 3. However, patient was lost to follow up and did not return for 2 years. The mass was biopsied at 2-year follow-up due to interval growth yielding mucinous carcinoma

Fig. 9

Fibroadenoma. Postcontrast subtraction T1-weighted sagittal (a) and axial (b) images show a 3.6-cm oval mass with circumscribed margins and dark internal septations. On c fat-saturated T2-weighted image, it demonstrated high signal intensity and is most consistent with a fibroadenoma. If this mass was an incidental finding on baseline MRI, a BI-RADS 3 assessment would be appropriate

Fig. 10

Mass with oval shape and circumscribed margins. a Postcontrast subtraction T1-weighted image shows a 0.6-cm oval-shaped mass with circumscribed margins and homogeneous internal enhancement, which demonstrated high signal on T2-weighted sequence (b) and a BI-RAD 3 assessment was given. 6-month follow-up MRI showed that this mass was stable and is likely an intramammary lymph node. This example shows that BI-RADS 3 assessment is appropriate for masses with an oval shape and circumscribed margins on baseline examination

Fig. 11

Focus with the absence of high signal on T2 sequence. a Postcontrast subtraction T1-weighted image shows a unique 0.4-cm focus with washout delayed kinetics (b) and the absence of high signal on fat-saturated T2-weighted image (c). Because this focus was new, it was assessed as probably benign, BI-RADS 3. Follow-up examination 6 months later showed increase in size of the focus; therefore, biopsy was recommended. MRI-guided wire localization was performed of this focus and surgery yielded invasive ductal carcinoma. For foci with washout kinetics and the absence of high T2 signal, biopsy should be considered

Fig. 12

Multiple regions of non-mass enhancement (NME) in the same breast. Postcontrast subtraction T1-weighted images a, b show multiple regions of NME, which are new but demonstrated persistent kinetics (c, d). These were assessed as probably benign, given the multiplicity, and were assumed to be transient enhancement related to hormonal status in this premenopausal woman. Follow-up exam 6 months later demonstrates slight increase in degree of enhancement (e, f); therefore, MRI-guided biopsy was recommended and yielded ductal carcinoma in situ (DCIS). Patient elected mastectomy yielding diffuse DCIS, no invasive component. New areas of NME should raise suspicion and biopsy should be considered

Fig. 13

Missed MRI-guided biopsy with follow-up demonstrating cancer. a Postcontrast subtraction T1-weighted image shows a 1.2-cm non-mass enhancement (NME) with focal distribution, heterogeneous internal enhancement, and b washout kinetics (arrow), which was suspicious and assessed as BI-RADS 4. MRI-guided biopsy was performed yielding fibrocystic changes and a 6-month follow-up MRI was recommended. At 6-month follow-up, c postcontrast subtraction T1-weighted image shows persistence of the NME and washout kinetics (d). Postcontrast T1-weighted image (e) shows that the susceptibility artifact from the biopsy marker clip is located posterior to the focal NME, which was unchanged in size and appearance suggesting that the NME was not biopsied. Surgical excision yielded carcinoma in situ