Overcalling low-risk findings: grouped amorphous calcifications found at screening mammography associated with minimal cancer risk

Because of the increasing availability of screening mammography and spread of information about its benefits, the incidence of early breast cancer has been increasing in Japan. However, screening mammography can result in overdiagnoses or false positives, causing in some subjects undergoing unnecessary invasive procedures. The current mammography guidelines recommend further investigation of subjects with grouped amorphous calcifications; this recommendation may have resulted in overdiagnoses or false positives. We retrospectively reviewed the charts of patients who had undergone screening mammography in the screening unit of our institution from January 2011 to December 2012 and been found to have grouped amorphous calcifications. Of the 233 such cases, 17 had been lost to follow-up, whereas whether the lesions were actually benign or malignant had been determined in the remaining 216 (92.7%). Six (2.8%) of 216 subjects with grouped amorphous calcifications were diagnosed as having malignancy and the remaining 210 (97.2%) as having benign lesions. Four of the six cases (1.9%) with malignancy had ductal carcinoma in situ and two (0.9%) 3 and 4 mm diameter invasive cancers of luminal type and nuclear grade 1. Grouped amorphous calcifications identified on screening mammography contribute minimally to detection of breast cancer and are not thought to be associated with any identifiable improvement in prognosis; present recommendations concerning this finding may result in false positives and overdiagnoses.