Primary synovial sarcoma arising from a crossed ectopic kidney with fusion.

Crossed renal ectopia with fusion is a rare anomaly of the kidney. The present case report describes a 67-year-old man with renal tumor who had been diagnosed as having a crossed ectopic kidney with fusion for 25 years. The pathological diagnosis of the primary tumor specimen was Wilms' tumor with favorable histology. Upon tumor recurrence, molecular detection of SYT-SSX2 fusion transcripts lead to the diagnosis of synovial sarcoma of the kidney. To our knowledge, this is the first case of primary synovial sarcoma arising from a crossed ectopic kidney with fusion.