Rare breast cancers with seemingly benign features on conventional imaging: Radio-pathological correlation and review of literature

Abstract

Oval or rounded breast masses with circumscribed margins, absence of microcalcifications, and architectural distortions are usually benign. However, 10-20% of breast cancers may have circumscribed margins, which may be misdiagnosed as benign breast mass or lead to delayed diagnosis in advanced stages of cancer. Most frequently, circumscribed breast cancers are high-grade invasive ductal carcinoma of triple-negative molecular subtype. However, there are many other rare histological subtypes of cancers in the breast with circumscribed margins or less aggressive features on imaging and mimic benign breast lesions. A radiologist needs to be familiar with the imaging features of various atypical malignant breast tumors to avoid delay in diagnosis. These rare malignant breast tumors are mucinous carcinoma, papillary carcinoma, lymphoma, leukemia, myeloma, metastasis from extramammary primaries, adenoid cystic carcinoma, signet-ring carcinoma, malignant phyllodes tumor, mesenchymal sarcoma, Ewing’s sarcoma, and medullary carcinoma. This pictorial review illustrates the clinical, multimodality imaging features of rare malignant breast tumors with less aggressive features on conventional breast imaging with pathological correlation.