Structural Diversity of Synovial Sarcoma (ss): an Optical, Ultrastructural and Molecular Biology Study of Original Tumors and Nude Mice Xenografts

Synovial sarcoma (SS) is one of the more common soft tissue sarcomas among young adults, accounting for 10 % of this group of malignant tumors. It arises mainly in deep soft tissue in the extremities, but a small number have been reported in other anatomical locations (Enzinger and Weiss, 2000). By definition, sarcomas are malignant neoplasms of mesenchymal origin, displaying a variety of differentiation characteristics, but lacking an epithelial component. The case of SS constitutes an exception within this context because of the presence of epithelial and mesenchymal elements, both malignant, simultaneously appearing within the same tumoral fields in close continuity. Based on these structures two main categories have been described. The SS presents a biphasic type, with epithelial and spindle cell components, and a monophasic type, exclusively constituted of the spindle cell component of the former. The latter, due to the lack of specific structures, may offer a complicated differential diagnosis with other malignant neoplasms such as fibrosarcoma, leiomyosarcoma and malignant peripheral nerve sheath tumor. Cytogenetically, a reciprocal translocation has been described, the t(x; 18)(p11.2; q11.2) is present in almost 100% of cases (Dal et al., 1992), being considered a specific marker (Antonescu et al., 2000, Kawai et al., 1998, Inagaki el al., 2000).