Grouped Amorphous Microcalcifications on Mammography: A Single-Centre 8-Year Retrospective Cohort Study on an Asian Population

Introduction: Grouped amorphous microcalcifications on mammography are classified as BI -RADS (Breast Imaging Reporting and Data System) category 4B. While recent international studies support a lower subcategory (4A), we sought to measure the malignancy rate of grouped amorphous microcalcifications classified as BI -RADS category 4A or above in the Asian population. Methods: All cases at our hospital with any kind of suspicious microcalcifications underwent either stereotacticguided vacuum -assisted biopsy or excisional biopsy with stereotactic localisation from 2013 to 2020 were retrieved. Cases with grouped amorphous microcalcifications as the most suspicious morphology on magnified views were selected. Only cases with at least 2 years of follow-up were included. Final histological diagnosis was based on the highest grade of tissue diagnosis at biopsy or excision. Results: Among 333 biopsied cases, 121 were grouped amorphous microcalcifications. The majority of patients (92.5%) were ethnic Chinese while the rest (7.5%) were Pacific Islanders. A total of 4.1% (n = 5) had malignant final pathology, with four ductal carcinomas in situ (DCIS) and one invasive ductal carcinoma. A total of 9.1% (n = 11) had high -risk pathology (all atypical ductal hyperplasia). In two cases, the microcalcifications were located adjacent to surgical scars, with one diagnosed as DCIS. Conclusion: The malignancy rate of grouped amorphous microcalcifications in our study is in line with recent studies, providing support for classifying a BI -RADS category 4A for these calcifications. The majority of the malignant lesions came back as DCIS, which carries promising post -treatment survival rates. Histological diagnosis remains indicated for grouped amorphous microcalcifications, yet more nuanced management plans may be employed in the future.