Lesions of uncertain malignant potential of the breast (B3) on vacuum-assisted biopsy for microcalcifications: Predictors of malignancy.

Purpose: To investigate clinical, radiologic and pathologic features of B3 lesions diagnosed on VABB targeting microcalcifications, for identifying predictors of malignancy.

Method: This retrospective multi-centre study included consecutive VABBs performed over a 10-year period on suspicious microcalcifications not associated with other radiological signs diagnosed as B3 on histology from VABB, with outcomes ascertained by surgical excision. Clinical, demographic, radiological and histological (B3 subcategory) data were collected. For statistical analysis (univariate and binary logistic regression), the primary outcome variable was the upgrade rate to malignancy after surgery. Predictors of upgrade to malignancy were identified from clinical, demographic, radiological and pathological variables (including B3 subcategory).

Results: Amongst 447 VABBs, there were 57(12.7 %) upgrades to malignancy at surgical histology (36 DCIS and 21 invasive cancer). At univariate analysis, variables significantly associated with increased risk of upgrade to malignancy were age>55 years (p = 0.01), lesion size>10 mm (p < 0.0001), BI-RADS 4b-c and 5 (p = 0.0001), and fine pleomorphic morphology (p = 0.002) of microcalcifications. Binary logistic regression confirmed as significant independent risk factors age, lesion size and BI-RADS category (p = 0.02, 0.02 and 0.0006 respectively). Amongst subcategories of B3 lesions, lobular neoplasia was significantly(p = 0.04) associated with upgrade, confirmed as an independent risk factor [p = 0.03, OR = 2.3(1.1-4.7)]. Flat epithelial atypia was significantly(p = 0.004) associated with reduced odds of upgrade, but binary logistic regression showed only borderline association [p = 0.052, OR = 0.4(0.2-1.01)].

Conclusions: Across B3 lesions diagnosed on histology from VABB of suspicious microcalcifications, older age, size>10 mm, BI-RADS category≥ 4b on imaging, and lobular neoplasia were risk factors for upgrade to malignancy. This information can be used to discuss patients' tailored management options.