Reappraisal of TLE-1 immunohistochemical staining and molecular detection of SS18-SSX fusion transcripts for synovial sarcoma.

The aim of the present study was to re-evaluate TLE-1 staining and the molecular detection methods of SS18-SSX transcripts for synovial sarcoma. We analyzed TLE-1 expression in 50 molecularly confirmed synovial sarcomas and 85 other soft tissue tumors with three previously published scoring systems. In the present study, 39 to 43 synovial sarcomas showed TLE-1 nuclear staining, whereas 9-15 of 85 other soft tissue tumors showed TLE-1 staining (P < 0.0001). The specificities of strong TLE-1 staining were 100%, 97.6% and 98.8%. The positive likelihood ratio of moderate and strong TLE-1 nuclear expression was >10 in all three scoring systems. There was no difference in TLE-1 staining between different subtypes of synovial sarcoma (P > 0.05). Based on a comparison between conventional reverse transcription (RT)-polymerase chain reaction (PCR) and fluorescence in situ hybridization (FISH), quantitative RT-PCR is a more sensitive method than conventional RT-PCR and FISH to detect t(X;18). A positive correlation between TLE-1 staining and SS18-SSX translocation was detected by conventional PCR (P < 0.05). In conclusion, although all three scoring systems could differentiate synovial sarcoma from other soft tissue tumors, diffuse moderate to severe intensity tumors showed the highest specificity in the diagnosis of synovial sarcoma.