Unusual Breast Malignancy: Correlation of MRI Findings with Pathologic Features

Most breast malignancies arise from epithelial elements and are categorized as carcinomas. IDC not otherwise specified (NOS) and ductal carcinoma in situ are common breast cancers and account for about 85% of breast cancers (1). Unusual breast malignancies may be broadly divided into ILC, well-differentiated subtypes of IDC, cancers of stromal origin, and metastatic neoplasms (2). Well-differentiated subtypes of IDC include mucinous carcinoma, tubular carcinoma, medullary carcinoma, papillary carcinoma, micropapillary carcinoma, apocrine carcinoma and metaplastic carcinoma (Table 1). However, we are not familiar to these unusual breast malignancies, and hesitate to interpret MRI findings of these tumors and correlate with pathologic features. In this article, we will provide an overview of unusual, as well as a few rare, malignant breast neoplasms and correlate multimodal breast imaging including MRI of these tumors with pathologic features.