Renal carcinoma manifesting as breast mass

A patient is described who initially presented with Stage I breast carcinoma and then with a T2, N0, M0 carcinoma of a kidney with moderately well-differentiated clear-cell features. Five years later, a contralateral breast mass developed which was histologically identical with renal primary tumor. Breast metastasis from renal primary carcinoma has been noted in the literature in 6 other cases, although this is only the third actual case report. This is the first case report of such a bizarre progression of disease. This patient is currently well, without clinically detectable tumor and illustrates the variable nature of metastatic renal cancer. The literature on renal cancer metastasizing to the breast is reviewed.