The Effective Use of Fluorescence in situ Hybridization on Touch Preparation Slides Permits a Timely Diagnosis of Synovial Sarcoma: Lessons Learned

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American Journal of Clinical Pathology


Introduction: The use of paraffin fluorescence in situ hybridization (FISH) analysis to identify SS18 ( SYT ) gene rearrangement associated with t(X;18)(p11.2;q11.2) provides a definitive diagnosis of synovial sarcoma. We present two illustrative cases of paraffin FISH analysis for SS18 rearrangement. The first case is a 25 year-old man with a left femur mass who underwent a core biopsy on a Friday. Frozen section analysis revealed a spindle cell neoplasm with high-grade features. The following Monday (3 days post resection), 16 immunohistochemical stains suggested but could not confirm a diagnosis of synovial sarcoma. Paraffin FISH was requested on Tuesday morning, and the result was available on Wednesday afternoon (5 days post resection). Unfortunately, earlier in that day (and still without a definitive diagnosis) the patient developed a left femur fracture. The second case involved a 17-year-old boy with a 5 cm left hip soft tissue mass.

Methods : Touch preparation for the second case was performed in the operating room and sent immediately for FISH evaluation. The next day, FISH confirmed SYT gene rearrangement. The FISH results were reported before routine H&E stained sections and immunohistochemical stains were available, and permitted case sign-out in less than 48 hours.

Conclusions: Comparing the utilization of permanent sections in case 1 and the touch preparation slides in case 2 illustrates the effectiveness of using the latter. It is now routine practice at our institution to prepare touch preparations immediately and order any FISH tests (based on frozen section diagnosis) up front. This process has significantly reduced turnaround time in many solid tumor cases.





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