Retroperitoneal cystic metastasis from a small clear cell renal carcinoma

A 39-year-old housewife was referred to our hospital for the treatment of a small renal tumor. A 25 × 35 mm cystic mass that had been detected by computerized tomography scan just caudal to the renal hilus proved to be a metastasis from the renal carcinoma of clear cell type. The pathogenesis may have been due to tumor cells obstructing a lymphatic vessel draining the kidney. Cystic metastasis from renal cell carcinoma is very rare and this appears to be the second published case in the world.