Assessment of malignant risk stratification for microcalcifications interpreted as "amorphous" morphology on mammography: A study based on the 5th edition of breast Imaging Reporting and Data System.

ABSTRACT

PURPOSE: To investigate the malignant risk stratification of microcalcifications interpreted as amorphous morphology on mammography according to the coexistence of punctate microcalcifications based on the 5th edition of the Breast Imaging Reporting and Data System. METHOD: Between March 2013 and September 2020, 367 microcalcifications interpreted as amorphous morphology on mammography with surgical biopsies were included. The amorphous microcalcifications were classified into a predominantly punctate group (A, <50% of amorphous), a predominantly amorphous group (B, >50% of amorphous), and an only amorphous group (C, 100% of amorphous). The distribution was classified into diffuse, regional, grouped, and linear/segmental. The reference standard was the pathology. The positive predictive values (PPV) were calculated and compared using the Chi-square's test or Fisher's exact test and Kruskal-Wallis test. RESULTS: The overall PPV of microcalcifications interpreted as having an amorphous morphology was 5.2%. The PPV across groups significantly increased in proportion to the amorphous morphology, with 1.0% in group A, 5.6% in group B, and 23.3% in group C (p <.001). Furthermore, the PPV between group A and groups B plus C (10.1%) and groups A plus B (2.8%) and group C were significantly different (p <.001). The PPV of distribution was 0% for diffuse, 4.9% for regional, 5.0% for grouped, and 11.1% for linear/segmental distributions, without statistical significance. CONCLUSIONS: Pure amorphous microcalcifications are suitable for category 4B. However, when they coexist with punctate morphology, the malignant risk decreases suitable for category 4A or lower. When amorphous microcalcifications coexist with a predominantly punctate morphology, follow-up should be considered.