Morphological and cytogenetic studies of a human synovial sarcoma xenotransplanted into nude mice.

Specimens of a synovial sarcoma from the left thigh of a 60-year-old woman and cells from the tumor transplanted into nude mice were examined morphologically and immunohistochemically, and the karyotype was analyzed. Immunohistochemically, cells of both the parent tumor and the transplanted tumor were positive for vimentin and cytokeratin. The multicystic features of the parent tumor were not reproduced in the mice. On ultrastructural examination, the parent tumor cells were found to have dilated channels of endoplasmic reticulum as well as a junctional apparatus, and they formed extracellular spaces. The transplanted tumor cells, in contrast, had a poorly developed endoplasmic reticulum and were devoid of extracellular spaces. Chromosome analysis of the tumor cells revealed a translocation, t (X; 18) (p11; q11), as reported previously for synovial sarcoma, thus suggesting the diagnostic utility of the chromosome pattern for identification of synovial sarcoma.