Purpose To compare positive predictive values (PPVs) of clumped versus non-clumped (homogenous and heterogenous) internal enhancement on MRI detected linear non-mass enhancement (NME) on MRI-guided vacuum assisted breast biopsy (MRI-VABB). Materials and Methods With IRB approval, radiology reports were retrospectively reviewed of 598 lesions undergoing 9-gauge MRI-VABB from January 2015 to April 2018 for lesions showing linear NME, recording clumped and non-clumped internal enhancement. We reviewed the electronic medical records for MRI-guided VABB pathology, any follow up surgery and imaging and/or clinical follow-up >1 year (mean 1.7 years). The X2 test was performed for univariate analysis. Results There were 120/598 (20%) linear NME MRI-VABB lesions with clumped (52/120, 43%) vs non-clumped (68/120, 57%) internal enhancement, average size 1.8 cm (range 0.3-7.6 cm). On MRI-VABB, cancer was identified in 22/120 (18%) lesions, ductal carcinoma in situ (DCIS) was found in 18/22 (82%) and invasive cancer (3 IDC, 1 ILC) in 4 (18%). 31/120 (26%) were high-risk lesions with 3/31 (10%) high-risk lesions upgraded to DCIS at surgery, which comprising a total of 25/120 (21%) malignancies. Malignancy was found in 12/52 (23%) clumped lesions and in 13/68 (19%) of non-clumped lesions that showed heterogenous (5/13, 38%) or homogenous (8/13, 62%) internal enhancement. The PPV of linear NME with clumped internal enhancement (23.1%; 95% CI, 11.6-34.6) was not significantly different from the PPV of non-clumped linear NME (19.1%; 95% CI, 9.8-28.4) (p=0.597). The PPV of linear NME lesions <1cm (33.3%; 95% CI, 11.5-55.1) was not significantly different from the PPV of lesions ≥1cm (18.6%; 95% CI, 11.1-26.2) (p=0.157). 53/120 (44%) NME lesions were operated upon. Of the remaining 67 NME not operated upon, 2 benign findings were lost to follow up, and 65 (64 benign, 1 high-risk) showed no suspicious imaging and/or clinical features on follow up. Conclusion Linear NME showed malignancy in 21% of our series. Linear NME with clumped or non-clumped internal enhancement patterns, regardless of lesion size, should undergo MRI-VABB in appropriate clinical settings.

Citation Format: Shu-Tian Chen, James Covelli, Satoko Okamoto, Bruce Daniel, Wendy DeMartini, Debra Ikeda. Clumped vs non-clumped internal enhancement patterns in linear non-mass enhancement on breast MRI [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-02-05.