Translocation t(9;22)(q22;q12) is a primary cytogenetic abnormality in extraskeletal myxoid chondrosarcoma

The cytogenetic and in vitro growth characteristics of 3 cases of extraskeletal myxoid chondrosarcoma (EMC) are described. In cell culture, the tumor cells retained the immunocytochemical and ultrastructural characteristics of EMC. Cytogenetically, 2 of the cases showed an apparently identical t(9;22)(q22;q12). In one case, the t(9;22) was found together with a dup(I)(q12q44), and in the other case it was found together with several other aberrations. The third case had an inv(10)(p11.2q22) as the sole karyotypic abnormality. Of 4 cases of EMC previously analyzed, 2 showed a t(9;22)(q22;q11-12) and one case of a t(9;22;15)(q31;q12.2;q25). Thus, 5 out of 7 cases of EMC showed recombination between 9q22-31 and 22q11-12, indicating that this represents a tumor specific abnormality. The breakpoints on 22q were in all 5 cases cytogenetically indistinguishable from those seen in Ewing's sarcoma with t(11;22), clear-cell sarcoma with t(12;22), and desmoplastic small round cell tumors with t(11;22). Molecular cloning of these translocation breakpoints revealed involvement of the EWS gene (located at 22q12) in all 3 tumor types. These observations raise the intriguing question of whether the EWS gene might also be involved in the t(9;22) in EMC.