Synovial sarcoma with relevant immunocytochemistry and special emphasis on the monophasic fibrous variant

Monophasic fibrous synovial sarcoma (SS) is the most common variant of SS. Only a few cytological studies are available on this entity. Bcl-2 protein expression has been described as a characteristic marker of SS and is useful for its differentiation from other sarcomas. Cytokeratin and CD99 are also used in detecting SS.

To evaluate synovial sarcoma and its variants cytomorphologically.

During a period of 10 years 7 months, i.e. from January 1998 to July 2008, 12 cytologic specimens diagnosed as synovial sarcoma were reviewed. Ten cases were diagnosed as SS on aspiration alone but two cases required ancillary technique i.e., immunocytochemistry staining with bcl-2 and cytokeratin. The smears were stained with Papanicolaou and May-Grünwald-Giemsa stains.

All cytologic specimens in our study had similar appearance. Most smears were highly cellular and were made up of densely packed tri-dimensional groups and singly scattered round to oval cells. Cellular monomorphism and vascular channels within the cell groups were the remarkable findings. Only one case showed cytologic evidence of epithelial differentiation. Bcl-2, cytokeratin, CD99 positivity was seen on immunohistochemistry staining. Results were categorized according to age, sex and morphologic variants.

Although cytomorphologic features of synovial sarcomas are characteristic enough to permit its recognition, clinical correlation is necessary for accurate diagnosis. Monophasic variant is the most common entity observed in the present study.