Usefulness and limitations of the Japan Mammography Guidelines for the categorization of microcalcifications

The Japan Mammography Guidelines, referred to the American College of Radiology Breast Imaging Reporting and Data System (BI-RADS), are intended to standardize the terminology in mammographic reports and the assessment of findings and to recommend action to be taken. The Japan Mammography Guidelines have explicit guidelines for the categorization of microcalcifications. The purpose of this study was to assess the positive predictive value (PPV) of each categorization of microcalcifications according to the decision table proposed by the Japan Mammography Guidelines according to BI-RADS morphology and distribution parameters and the pathologic outcome.

A retrospective review was performed of 101 non-palpable screening mammography-detected microcalcification lesions without mass that had stereotactic vacuum-assisted breast biopsy (SVAB). This study was approved by our institutional review board, and informed consent was obtained for all SVAB. We classified microcalcification lesions according to the decision table. Histological findings were reviewed.

In calcification morphology, all 32 punctate morphology microcalcifications, regardless of distribution, were benign (100%), whereas 25% (9/36) amorphous morphology microcalcifications, 67% (14/21) pleomorphic morphology microcalcifications and 92% (11/12) linear morphology microcalcifications were malignant. For calcification distribution, 28% (15/55) cluster distribution microcalcifications, 40% (17/43) segmental distribution microcalcifications and 67% (2/3) linear distribution microcalcifications were malignant. Features with high positive PPV showed segmental or linear distribution of linear morphology (100%, respectively), segmental distribution of pleomorphic morphology (100%) and cluster distribution of linear morphology (80%). The PPV for cluster punctate, cluster amorphous, cluster pleomorphic and cluster linear microcalcifications was 0, 21, 50 and 80%, respectively. The PPV for segmental punctate, segmental amorphous, segmental pleomorphic and segmental linear microcalcifications was 0, 27, 100 and 80%, respectively. The PPV for linear amorphous and linear linear microcalcifications was 50 and 100%.

The decision table proposed by the Japan Mammography Guidelines according to BI-RADS morphology and distribution parameters is useful, but continued development of the decision table to improve standardization in mammographic interpretation is needed.