Lobular neoplasia detected at MRI-guided biopsy: imaging findings and outcomes.

OBJECTIVE To review MRI findings of pure lobular neoplasia (LN) on MRI guided biopsy, evaluate surgical and clinical outcomes, and assess imaging findings predictive of upgrade to malignancy. METHODS HIPAA compliant, IRB-approved retrospective review of our MRI-guided breast biopsy database from October 2008-January 2015. Biopsies yielding atypical lobular hyperplasia or lobular carcinoma in situ were included in the analysis; all biopsy slides were reviewed by a dedicated breast pathologist. Imaging indications, MRI findings, and histopathology were reviewed. Statistical analysis was performed using the two-tailed Fisher exact-test and the t-test, and 95% CIs were determined. A p < 0.05 was considered statistically significant. RESULTS Database search yielded 943 biopsies in 785 patients of which 65/943 (6.9%) reported LN as the highest risk pathologic lesion. Of 65 cases, 32 were found to have LN as the dominant finding on pathology and constituted the study population. All 32 findings were mammographically and sonographically occult. Three of 32 (9.3%) cases of lobular neoplasia were upgraded to malignancy, all LCIS (one pleomorphic and two classical). The most common MRI finding was focal, heterogenous non-mass enhancement with low T2 signal. No clinical features or imaging findings were predictive of upgrade to malignancy. CONCLUSION Incidence of pure lobular neoplasia on MRI guided biopsy is low, with comparatively low incidence of upgrade to malignancy. No imaging or clinical features are predictive of upgrade on surgical excision, therefore, prudent radiologic-pathologic correlation is necessary.