Stratifying Risk for Malignancy Using Microcalciication Descriptors from the Breast Imaging Reporting and Data System 4th Edition: Experience in a Single Centre in Hong Kong

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KKK Chan, CY Lui, T Chu, KK Chan, AT Yan, K Wong, PY Fung, LK Chan, HS Lam

Hong Kong J Radiol 2009;11:149-53

Objective: To evaluate whether categorisation of microcalcification descriptors based on the Breast Imaging Reporting and Data System 4th edition can stratify the risk for malignancy using pathology results of biopsies as the gold standard.

Methods: This retrospective study included 390 biopsies of 399 patients with microcalcifications treated at Kwong Wah Hospital, Hong Kong, from July 2005 to September 2007. Three subspecialty-trained breast radiologists (observers) interpreted copy films of mammograms, and classified them into 1 of the 5 Breast Imaging Reporting and Data System morphological calcification descriptor groups of benign, coarse heterogeneous, amorphous, fine pleomorphic, and fine linear. The number of malignancies in each group was compared and interobserver variability was assessed using the k coefficient.

Results: Seventy seven of 390 biopsies (19.7%) demonstrated malignancy. The average percentages of malignancies were 7.8% for the benign group, 19.7% for the coarse heterogeneous group, 15.1% for the amorphous group, 53.0% for the fine pleomorphic group, and 86.0% for the fine linear group. The Breast Imaging Reporting and Data System 4th edition helped to stratify the percentage of malignancies in the high-probability group compared with the intermediate-concern and benign groups for all 3 observers (odds ratio, 15.0; 95% confidence interval, 7.49-29.60; odds ratio, 4.5; 95% confidence interval, 2.60-7.58; and odds ratio, 14.1; 95% confidence interval, 7.00-28.00, respectively). The percentage of malignancies was also significantly higher in the fine pleomorphic group when compared with the coarse heterogeneous group for 2 of the 3 observers. However, interobserver agreement was modest (k coefficient = 0.24).

Conclusions: Microcalcification descriptors in the Breast Imaging Reporting and Data System 4th edition can stratify risk for malignancy of highly suspicious microcalcifications for the benign and intermediateconcern groups using local data. For 2 of the 3 observers, further differentiation of pleomorphic calcification into fine pleomorphic and coarse heterogeneous groups helped to stratify risk for malignancy. The quality of the copy films may have accounted for the high interobserver variability.