Mammographic focal asymmetries with interval increase: ultrasound and MRI correlation with histopathologic outcomes.

PURPOSE: To evaluate the ultrasound (US), magnetic resonance imaging (MRI), and histopathologic findings of enlarging focal asymmetries detected on mammography, to determine their benign and malignant causes, and to assess the rate of malignancy and imaging correlations. METHODS: This retrospective study included 117 patients diagnosed with enlarging focal asymmetry on screening mammography. Targeted US was performed in 83 patients (71%), MRI in 71 patients (61%), and both modalities in 51 patients (44%). Histopathologic correlation was available in 35 cases. Lesions with at least 2 years of stability were considered benign. The rates of malignancy and imaging correlation were analyzed. RESULTS: Among 117 enlarging focal asymmetries, 12 (10%) were malignant and 5 (4%) were high-risk lesions. Of the high-risk lesions, one (20%) was upgraded to malignancy after surgery. Targeted US and MRI correlation rates were 57% and 51%, respectively. In histopathologically proven cases, both modalities showed 100% correlation. Seventeen cases were diagnosed as cysts or benign lesions with targeted imaging, and the remaining 65 cases (56%) were considered summation artifacts. CONCLUSION: Although most enlarging focal asymmetries are benign or due to summation artifacts, they remain an important indicator for potential malignancy. Correlation with targeted US and MRI significantly aids in distinguishing benign or summation-related findings from those requiring biopsy.