Lobular neoplasia occult on conventional imaging and diagnosed on MRI-guided biopsy: can we estimate upgrade on surgical pathology?

The goal of this study is to evaluate the frequency and imaging features of lobular neoplasia (LN) diagnosed on MRI-guided biopsy, determine the upgrade rate to malignancy, and assess for any features that may be associated with an upgrade on surgical excision. Research ethical board approved the review of consecutive patients with MRI-detected LN between January 2009 and December 2018 with differentiation between pure LN and LN with associated other high-risk lesions. The final outcome was determined by final pathology results from surgical excision or 24 months of follow-up. Appropriate statistical tests were used. Out of 1250 MRI-guided biopsies performed, 76 lesions (6%) fulfilled the inclusion criteria and formed the study cohort. Of the 76 lesions, 54 (71%) were pure LN while the rest had coexistent high-risk lesion. Non-mass enhancement (NME) was the most common lesion type (62, 82%). Fifty-nine lesions (78%) were surgically excised, the other 17 had benign follow-up. Overall, 8 lesions (11%) were upgraded to malignancy on final pathology. Malignant outcome was associated with larger lesion size (5.5 versus 1.9 cm, P < 0.001) and a clumped NME pattern (75% versus 24%, P = 0.006). Lesion size and clumped NME remained significantly associated with upgrade on sub-analysis of the pure LN group. Larger lesion size and clumped NME are imaging findings associated with upgrade of LN diagnosed by MRI-guided biopsy. This may influence patient management in this clinical setting. Additional larger studies are needed to consolidate our results and to potentially detect additional factors associated with upgrade.