Metastases to the Breast

Abstract

Metastases to the breast are rare, yet correct identification of a neoplasm as a metastasis is imperative for patient treatment as well as prognosis. Non-hematopoietic, solid organ metastases to the breast account for approximately 0.2--1.2 % of all breast neoplasms. In adults, melanoma is the single most common solid organ neoplasm to involve the breast, followed by pulmonary and ovarian carcinomas. In the pediatric/adolescent population, metastases to the breast outnumber primary breast neoplasms, with rhabdomyosarcoma being the most common neoplasm to involve the breast. Metastases to the breast present a diagnostic challenge due to the overlapping morphologic features with primary breast carcinoma. Certain histologic features may suggest that a lesion is not a primary breast neoplasm, such as estrogen receptor-negativity in a well-differentiated adenocarcinoma (suggestive of pulmonary or gastrointestinal adenocarcinoma), psammomatous calcifications in an adenocarcinoma with micropapillary features (suggestive of papillary serous carcinoma), and melanin pigment in a high-grade epithelioid neoplasm (suggestive of melanoma). A thorough clinical history, a clinical work-up, and a targeted immunohistochemical panel are often necessary to reach the correct diagnosis.