Tumor-to-tumor metastasis (TTM) of breast carcinoma within a solitary renal angiomyolipoma: a case report.

Angiomyolipomas of the kidney have been known to harbor malignant neoplasms including renal cell carcinoma. We report a case of a tumor-to-tumor metastasis (TTM) involving metastatic breast carcinoma and angiomyolipoma. The patient was a 67-year-old female with a history of invasive ductal carcinoma of the breast. Follow-up positron emission tomography 9 years later revealed a left renal mass, suspicious for a primary renal neoplasm, as well as a suspicious subpectoral lymph node. An ultrasound-guided needle biopsy of the lymph node demonstrated metastatic breast carcinoma. The patient underwent a left radical nephrectomy. Pathologic examination demonstrated an ill-defined 2cm estrogen receptor (ER)-positive metastatic breast carcinoma within a 6cm angiomyolipoma. To our knowledge, this is the first reported case of metastatic breast carcinoma to a solitary renal angiomyolipoma. This case highlights the importance of a patient's prior history of malignancy, as well as appropriate sampling of renal neoplasms.