Metachronous metastasis to contralateral retroperitoneal adipose tissue after radical nephrectomy: a case report and review of the literature.

Renal cell carcinoma (RCC) metastasis to the adrenal gland, perirenal adipose tissue, and ureter on the contralateral side is rare. We report a case of solitary metachronous clear cell renal cell carcinoma (ccRCC) metastasis to the contralateral retroperitoneal adipose tissue, which was identified after radical nephrectomy. A patient had undergone retroperitoneal laparoscopic radical nephrectomy for RCC in the right kidney in December 2012. Postoperative pathological analysis showed Fuhrman grade I ccRCC, T1bN0M0. Three years after surgery, a solitary tumor of 1.0 × 1.0 cm was identified by an abdominal computed tomographic scan inside the retroperitoneal fat pad in front of the left posterior abdominal wall, without adhesion to the abdominal wall. The tumor was then completely resected by retroperitoneal laparoscopic resection. Pathological analysis showed that it was a metastasized lesion from a previous tumor. Nine months after surgery, there was no sign of recurrence confirmed by radiographic follow-up. Findings from this case indicate the unpredictability of dissemination of RCC. Our findings support a follow-up regimen that includes regular postoperative computed tomographic scans to identify early metastasis. To the best of our knowledge, this is the first reported case of contralateral retroperitoneal adipose metastasis after laparoscopic tumorectomy.