Synovial Sarcoma : Immunostains CD99

Comments:
Additional immunohistochemical markers expressed in synovial sarcomas include: CD99 (shown here; product of MIC2 gene; 60-70% of cases), BCL2 (expressed in most cases; especially in spindle cells), calponin, calretinin, desmoplakin ZO-1 (specialized cell-junction associated protein), claudin-1, and occludin.

About 30% of synovial sarcomas express S-100 protein creating confusion with MPNST. In such cases, the expression of CK7, CK19, TLE1, and/or molecular genetic studies can help with the diagnosis. Image courtesy of: Evita Sadimin, MD (@ESadimin); used with permission