The authors present two cases of primary synovial sarcoma of the kidney. Both patients had a tumor mass in the kidney with vascular invasion of the inferior vena cava and right atrium of the heart in case no. 1. In case no. 2 retroperitoneal lymph node metastasis and multiple metastases to both lungs were observed. Radical nephrectomies were performed in both patients. Histologically, the tumor in case no. 1 was monophasic and in case no. 2 poorly differentiated. Immunohistochemically, vimentin was diffusely positive and a few tumor cells were positive for epithelial membrane antigen. The tumor cells were negative for keratins, S- 100 protein, CD 34, smooth muscle actin, and desmin. In both cases, reverse transcription-polymerase chain reaction using ribonucleic acid extracted from formalin-fixed, paraffin-embedded tissues detected SYT-SSX 1 fusion gene transcripts, which are characteristic molecular findings of synovial sarcoma.

        Key words: synovial sarcoma – kidney – SYT-SSX – RT-PCR