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.