Histological features, diagnostic evaluation, and genomic alterations

Synovial sarcoma can be subclassified as the following types:

The diagnosis of synovial sarcoma is made by immunohistochemical analysis, ultrastructural findings, and demonstration of the specific chromosomal translocation t(x;18)(p11.2;q11.2). This abnormality is specific for synovial sarcoma and is found in all morphological subtypes. Synovial sarcoma results in rearrangement of the SS18 gene on chromosome 18 with one of the subtypes (1, 2, or 4) of the SSX gene on chromosome X.[13,14] It is thought that the SS18::SSX fusion transcript promotes epigenetic silencing of key tumor suppressor genes.[15]

In one report, reduced SMARCB1 nuclear reactivity on immunohistochemical staining was seen in 49 cases of synovial sarcoma, suggesting that this pattern may help distinguish synovial sarcoma from other histologies.[16]