A distinct calcification pattern is one of the criteria for determining the malignancy of breast cancer according to the Breast Imaging Reporting and Data System. A mass almost entirely replaced by calcification, however, is difficult to categorize and likely to be misdiagnosed. We present the report of two patients with invasive carcinoma of the breast that presented as a mass replaced by calcification on mammography. In the first case, the mass was confirmed as a mixed carcinoma comprising mucinous and micropapillary carcinoma, and in the second case, the mass was a mucinous carcinoma. Diagnosis of cancer in the latter case was missed as the mass had been assessed as a category 2 typically benign calcification at the first screening mammography 2 years ago. This report merits publication because it shows that a mass replaced by calcification on mammography can be misdiagnosed as a benign finding.
