Metastases to breast simulating ductal carcinoma in situ: report of two cases and review of the literature.

The breast is an uncommon site for metastases. Nevertheless, it is important to differentiate primary from secondary tumors of the breast, because clinical management and expected outcomes are vastly different. We report two examples of tumors with a papillary histologic pattern metastasizing to the breast. One of the cases occurred in a 31-year-old woman with a primary renal cell carcinoma, the other was in a 42-year-old woman with an ovarian papillary serous adenocarcinoma. In the first case, the patient's previous history of cancer was not known to the pathologist. The cases highlight the difficulty in distinguishing primary from metastatic tumors in the breast. In both cases the tumors infiltrated in a pattern that mimicked in situ ductal carcinoma changes. Additionally, in both cases, the metastasizing tumor was unusual with the tumor cells diffusely permeating the lymphatic spaces, not in a solid mass. These cases and a review of the literature indicated that breast metastases, although rare, must be recognized and differentiated from primary breast tumors to avoid unnecessary radical surgery to the breast. Moreover, the presence of changes similar to in situ carcinoma of the breast are not conclusive evidence that one is evaluating a primary breast carcinoma. When there is any unusual histomorphology, a good degree of suspicion is necessary. Ann Diagn Pathol 5:15-20, 2001. Copyright 2001 by W.B. Saunders Company