Intramammary Metastases from Extramammary Malignancies: An Update

Purpose of Review Metastases to the breast (intramammary metastases, IM) from extramammary malignancies (EM) are uncommon. As prognosis is poor, timely diagnosis is key to direct patients towards appropriate treatment. We will review recent literature regarding the epidemiology, presentation, and diagnosis of IM. Recent Findings IM commonly present as palpable masses, with imaging findings often based on hematogenous versus lymphatic spread. While many IM are diagnosed with a history of EM, IM may also be the first presentation of distant metastatic disease. In most cases, immunohistochemical testing is required to differentiate between primary breast cancer (PBC) and IM. Summary Recent research, focused on immunohistochemical markers, can guide diagnosticians in differentiating IM from PBCs. Key factors to consider when diagnosing any breast mass include a prior history of cancer, imaging characteristics, histologic findings that are atypical for PBCs, and the immunohistochemical profile of each lesion.