Abstract

Synovial sarcoma most commonly affects the extremities, especially the lower thigh and knee region. However, a smaller number develops in a central or axial distribution, an area which encompasses the trunk, orofacial, cervical and parapharyngeal regions. The retroperitoneum is an extremely unusual site and has never been recorded in the literature as primary a site for synovial sarcoma. We investigated a case of retroperitoneal synovial sarcoma in a 40-year-old woman. The specimen consisted of fragmented large bulky multinodular masses separated by slit-like spaces. The tumor was 130 gm in weight. Microscopically, the tumor was composed of nests of plump ovoid to polygonal shaped cells and bundles of spindle shaped cells, which had vesicular nuclei and a small amount of cytoplasm. In some areas, there were cleft like spaces and pseudoglandular structures lined by flat or cuboidal cells. Myxoid change, collagen deposition, foci of calcification and osseous metaplasia were also present. Immunohistochemically, the polygonal cells and some of the spindle cells reacted positively for keratin. The spindle cells, especially in the perivascular area were positive for vimentin. S-100 protein and GFAP were negative in both type of cells.

• Keywords: Retroperitoneal tumor;Synovial sarcoma;