FISH, Synovial Sarcoma, SYT, 18q11.2 Rearrangement

Laboratory assay overview

This fluorescence in situ hybridization (FISH) assay detects the chromosome rearrangements that involve the SS18 (SYT) gene on chromosome 18q11.2. The results of this test may aid in the diagnosis of synovial sarcoma. Synovial sarcoma is a soft tissue sarcoma that mainly occurs in the extremities. A histologic and immunohistochemical diagnosis can be difficult because synovial sarcoma often resembles other spindle-cell sarcomas. The majority of the patients with synovial sarcoma have SS18 gene rearrangements, which result in the t(X;18)(p11;q11) with SS18/SSX1 gene fusion, t(X;18)(p11;q11) with SS18/SSX2 gene fusion, and t(X;18)(p11;q11) with SS18:SSX4 gene fusion [1,2].The SS18/SSX1 fusion gene occurs in two-thirds of the patients with synovial sarcoma; the SS18/SSX2 fusion gene occurs in one-third of the patients; the SS18/SSX4 fusion gene rarely occurs [2]. Another rare fusion gene, SS18L1/SSX1, is a result of the t(X;20) translocation and cannot be detected by this FISH test [3]. The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings. References 1. National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®). Soft tissue sarcoma. Version 2.2023. Updated April 25, 2023. https://www.nccn.org 2. Fletcher CDM, et al. Soft tissue tumours. In: WHO Classification of Tumours Editorial Board. Soft tissue and bone tumours. 5th ed. IARC Press; 2020:chap 2. Accessed July 18, 2023. https://tumourclassification.iarc.who.int 3. Storlazzi CT, et al. Genes Chromosomes Cancer. 2003;37(2):195-200.