Abstract Purpose: To evaluate abnormal interpretation/recall rates, imaging findings, and outcomes for asymptomatic lactating women at elevated lifetime risk of breast cancer screened with mammography (MG) and/or breast MRI. Methods: An IRB-approved, HIPAA-compliant retrospective chart review was conducted at a tertiary academic center (2013-2024). Patients were included if lactating and undergoing breast cancer screening due to a personal history of breast cancer, strong family history, or hereditary breast cancer predisposition. Screening was performed with MG, MRI, or both during lactation. Imaging findings were defined using American College of Radiology Breast Imaging Reporting and Data System (BI-RADS 5th ed.). Final outcomes were verified via histopathology or ≥2 years of clinical/imaging follow-up; patients without this were excluded. Results: Of 118 patients identified, 9 were excluded for insufficient follow-up. Among 109 included patients, 63 underwent MG (58 with tomosynthesis), and 45 had MRI. Mean age was 37 ± 4 years (range 27–47) for the MG group and 34 ± 3 years (range 26–43) for the MRI group. Overall, 84% had a first-degree family history of breast cancer, 13% were BRCA2+, 9% BRCA1+, and 8% had a prior breast cancer diagnosis. In the MG group, 30% were baseline screening exams and 70% were subsequent screening exams. Breast density was 54% extremely dense and 48% heterogeneously dense. BI-RADS assessments included 41 BI-RADS 1 (negative) and 16 BI-RADS 2 (benign). The recall rate was 9% (n = 6), based on BI-RADS 0 assessments, for an asymmetry (n = 1), mass (n = 2), calcifications (n = 2), and possible architectural distortion (n = 1). Diagnostic imaging for the recalled cases yielded 4 benign/negative results, 1 BI-RADS 4A mass confirmed as fibroadenoma on US-guided biopsy, and 1 BI-RADS 3 finding with stable calcifications on follow-up imaging. In the MRI group, 40% were baseline screening exams and 60% were subsequent screening exams. Breast composition was 67% extremely dense and 29% heterogeneously dense. Background parenchymal enhancement (BPE) was marked in 62%, moderate in 16%, and mild/minimal in 22%. BI-RADS assessments were 41 BI-RADS 1 and 16 BI-RADS 2. The abnormal interpretation rate was 9% (n = 4). Both BI-RADS 0 cases showed axillary lymphadenopathy: US was benign (BI-RADS 2) in one and suspicious (BI-RADS 4) in the other (biopsy-confirmed benign lymph node). One BI-RADS 4A case (focal non-mass enhancement) was benign breast tissue with dense stromal fibrosis on histopathology from MRI-guided biopsy. The other BI-RADS 4A case (mass) was benign lactational changes in accessory axillary tissue on histopathology from US-guided biopsy. No cancers were detected. Conclusion: Screening recall and abnormal interpretation rates were low in both the MG and MRI groups and fell within the acceptable range for screening MG performance (5-12%). Although no pregnancy-associated cancers were diagnosed, findings support continued adherence to high-risk screening during lactation. Screening high-risk lactating patients is potentially challenging due to physiologic changes in breast density and BPE which can cause false-positive and false-negative results. This study demonstrates that screening MG and breast MRI are practical tools in the high-risk lactating population. Citation Format: A. Keller, M. Elezaby, L. Salkowski, R. Strigel, A. Fowler. Screening Mammography and Breast MRI in High-risk Lactating Patients abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS1-06-10.
Keller et al. (Tue,) studied this question.