Subcategorization of ultrasonographic BI-RADS category 4: positive predictive value and clinical factors affecting it.

The objective of this study was to evaluate the positive predictive value (PPV) in ultrasonographically (US)-detected breast lesions of BI-RADS category 4a, 4b and 4c and to find how various clinical factors influenced the PPV of category 4. A total of 2142 women with 2430 breast lesions diagnosed on US as BI-RADS category 4 and underwent biopsy were included. Among them, 452 (18.6%) were pathologically confirmed as malignancy. PPV of each US BI-RADS subcategory was 7.6% (149/1963) for category 4a, 37.8% (68/180) for category 4b and 81.9% (235/287) for category 4c. Several clinical factors were more significantly seen in malignancy of category 4a and 4b, whereas none of the factors showed significance in category 4c. Subcategorization of category 4 is a feasible method in predicting malignancy in which patients' age, lack of multiplicity and symptoms affected the PPV of category 4 lesions.