E5260. Triple-Negative Tumors of the Breast: Beware of Potential Extramammary Origin
  1. Jennifer Farah; No Affiliation
  2. Mona El Khoury; No Affiliation
  3. Maude Labelle; No Affiliation
  4. Isabelle Trop; No Affiliation
Metastases to the breast from extramammary solid primary tumors are rare and account for less than 1% of all breast malignancies. The most common primaries that metastasize to the breast include melanoma, lung cancer, and ovarian cancer. This most often occurs through a hematogenous spread, resulting usually in multiple, well-delineated, superficial masses, without calcifications or surrounding desmoplastic reaction. Rarely, a solitary benign appearing mass or an isolated enlarged intramammary lymph node can result from hematogenous spread of an extramammary cancer. Secondary neoplastic breast involvement may also less likely occur through the lymphatic route, presenting clinically, not as masses, but as diffuse erythema and swelling due to infiltration of the dermal lymphatics hence, mimicking inflammatory breast cancer. This has been rarely described with ovarian and lung cancers as well as gastric and endometrial carcinomas. Regardless of their mode of spread, metastatic lesions in the breast usually indicate late stages and poor prognosis. Because breast metastases are rare, and primary breast cancer is prevalent, a new breast mass is more likely to represent a new primary breast tumor even in a patient with a history of an extramammary malignancy. Recognizing these metastases from primary breast tumors is crucial for appropriate management.

Educational Goals / Teaching Points
1) Describe some unusual appearances and presentations of metastatic tumors in the breast. 2) Raise more awareness to the possibility of a solitary metastatic lesion in the breast from an extramammary solid primary lesion. 3) Encourage radiologists to keep in mind the clinical information and the past medical history of the patient.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
On pathology, metastatic lesions usually have a triple-negative signature. Triple-negative breast cancer is a form of aggressive breast cancer that can present as a benign-looking lesion without a desmoplastic reaction. It is usually treated with neoadjuvant chemotherapy followed by surgical resection, whereas metastases are managed differently, depending on the type of primary cancer and the extent of disease. The key to accurate diagnosis is histologic examination with immunohistochemistry; however, this should be guided by the radiologist’s suspicion for the right markers to be examined. Thus, a high degree of suspicion is necessary.

In our presentation, we will highlight, through clinical cases, the rare radiological presentations of breast metastases such as solitary metastases to the intramammary lymph node as well as secondary inflammatory breast involvement through lymphatic spread mimicking inflammatory breast cancer. Radiologists should be aware of the typical and untypical presentations of breast metastases as well as the clinical and past medical history of the patient to help reach the correct diagnosis and avoid mismanagement.