Grouped Amorphous Calcifications at Mammography: Frequently Atypical but Rarely Associated with Aggressive Malignancy.

Purpose To determine rate of malignancy at stereotactic biopsy of amorphous calcifications with different distributions using current imaging, clinical, and histopathologic criteria. Materials and Methods From January 2009 to September 2013, this retrospective study reviewed a large set of stereotactic biopsies to identify amorphous calcifications and their clinical, imaging, and histopathologic characteristics. Calcification distribution was correlated with malignancy rate after adjusting for known risk factors using logistic regression. Results Of 1903 sequential biopsies, 546 (28.7%) were for amorphous calcifications. After excluding atypical lesions not excised and patients with more than one biopsy in the same year, 497 lesions from 494 women (median age, 52 years; age range, 30-81 years) remained. Fifty-two (10.5%; 95% confidence interval [CI]: 7.9, 13.5) lesions proved malignant, with 17 of 52 (42.7%) being invasive cancers (median, 0.3 cm; range, 0.1-1.3 cm) and all 17 of them being estrogen and progesterone receptor positive and node negative. Malignancy rates in a segmental (six of 21 [28.6%]), linear (eight of 32 [25.0%]), or multiple group same quadrant (nine of 36 [25.0%]) distribution were significantly higher than malignancy rate in a solitary group of amorphous calcifications (25 of 356 [7.0%]) (P = .004, P = .003, and P = .002, respectively). Of 356 grouped amorphous calcifications, 102 (28.7%) yielded atypical results prompting excision, with three of 102 (2.9%) upgraded to ductal carcinoma in situ at excision. In women younger than 50 years without a personal history of cancer, grouped amorphous calcifications showed four of 127 (3.1%) (95% CI: 0.9, 7.9) were malignant and 39 of 127 (30.7%) were atypical at final histopathology. Conclusion Biopsy of amorphous calcifications remains necessary, with an overall malignancy rate of 10.5%; only 17 of 497 (3.4%) biopsies showed invasive cancer, and all of these were estrogen and progesterone receptor positive. Grouped amorphous calcifications in women younger than 50 years without history of breast or ovarian cancer showed a low malignancy rate of 3.1% (four of 127). © RSNA, 2018 Online supplemental material is available for this article.