Cytologic features of synovial sarcoma with emphasis on the monophasic fibrous variant: a morphologic and immunocytochemical analysis of bcl-2 protein expression.

BACKGROUND

Monophasic fibrous synovial sarcoma (SS) is the most common variant of SS but few cytologic studies concerning this entity are available. bcl-2 protein immunoexpression has been described as a characteristic marker of SS and is useful for its differentiation from other sarcomas.

METHODS

Twelve cytologic specimens from 11 patients with histologically proven SS were reexamined. Ten samples were obtained by fine-needle aspiration and in two cases fluid from cystic tumoral areas was obtained at surgery. Nine cases corresponded to monophasic fibrous tumors and two to biphasic tumors. Immunoexpression of bcl-2 was evaluated in all histologic specimens and in six cytologic samples. bcl-2 protein also was evaluated in 13 soft tissue tumors.

RESULTS

All cytologic specimens had a similar appearance. Most smears were highly cellular and were comprised of densely packed, tridimensional groups and numerous isolated, round to oval cells. Remarkable findings included cellular monomorphism and vascular structures within the cell groups. Only one case showed cytologic evidence of epithelial differentiation. Immunoexpression of bcl-2 protein was present in 10 of the 11 histologic specimens (90.9%) and in 5 of the 6 cytologic samples (83.3%). A positive result also was observed in malignant fibrous histiocytoma, dermatofibrosarcoma protuberans, infantile hemangiopericytoma, pleomorphic liposarcoma, and malignant solitary fibrous tumor.

CONCLUSIONS

Although cytomorphologic features of SS are characteristic enough to permit its recognition, clinical correlation is necessary for its correct diagnosis. The immunoexpression of bcl-2 protein is not specific of SS and other soft tissue tumors can show a similar positive reaction.