Frequency, upgrade rates, and characteristics of high-risk lesions initially identified with breast MRI.

Objective: The purpose of this article is to determine the frequency, outcomes, and imaging features of high-risk lesions initially detected by breast MRI, including atypical ductal hyperplasia, atypical lobular hyperplasia, lobular carcinoma in situ, and radial scar.
Materials and Methods: A retrospective review of our MRI pathology database was performed to identify all lesions initially detected with MRI (January 2003 through May 2007) that underwent imaging-guided needle biopsy yielding high-risk histopathologic abnormalities. Patient age, clinical indication, MRI BI-RADS lesion features, biopsy method, and histopathologic diagnosis were recorded. The frequencies of high-risk findings at needle biopsy and rates of upgrade to malignancy at surgical excision were compared across lesion imaging features with Fisher's exact test.
Results: Four hundred eighty-two MRI-detected suspicious lesions underwent needle biopsy. High-risk histopathologic abnormalities were present in 61 (12.7%) of 482 lesions: 51 (10.6%) atypical ductal hyperplasias, six (1.2%) atypical lobular hyperplasias, three (0.6%) lobular carcinomas in situ, and one (0.2%) radial scar. Correlation between the lesion site and pathology at surgical excision was confirmed for 39 of 61 lesions. Twelve (30.8%) of those 39 lesions were upgraded to malignancy (11 atypical ductal hyperplasias and one atypical lobular hyperplasia); five (41.7%) of the 12 malignancies were invasive cancer, and seven (58.3%) were ductal carcinomas in situ. No significant lesion features predictive of subsequent upgrade to malignancy were discovered.
Conclusion: There are no specific imaging features that predict upgrade for high-risk lesions when detected with MRI. Therefore, surgical excision is recommended because upgrade to invasive carcinoma or ductal carcinoma in situ can occur in up to 31% of cases, regardless of biopsy technique.