Metastatic Tumors to the Breast from Extramammary Malignancies

Background : Metastases to the breast from extramammary malignancies are very rare. We describe here the clinicopathologic features of the metastatic breast tumors that were identified in Korean patients at a single institute. Methods : We analyzed the clinicopathologic data of the patients who were diagnosed between January 1989 and April 2009 at Asan Medical Center. Results : Only 31 (0.21%) patients with metastases to the breast from extramammary malignancies were diagnosed over a 20-year period, and 29 of them had available data. The mean time to the diagnosis of metastasis after the diagnosis of the primary malignancy was 21 months (range, 0 to 102 months). The most common primary site was the stomach, followed by the uterus and lung. The most common histologic type was adenocarcinoma. A common clinical presentation was a unilateral palpable mass. Most metastatic tumors had morphological features that were similar to those of their respective primary tumors. However, in situ carcinoma, microcalcification and desmoplastic reactions were rarely observed. Conclusions : Metastatic breast lesions from extramammary sites are extremely rare, and the stomach, uterus and lung could be considered as the common primary sites in Korean patients. The clinical history and comparing the morphology of the primary tumor with the morphology of the metastatic tumor are important for achieving the proper diagnosis.