Chromosomal abnormalities in two chordomas.

Cytogenetic analyses of two sacral chordomas are reported. Both tumors showed clonal chromosome abnormalities, including numerical and structural aberrations. The modal chromosome numbers were 36 and 72, respectively. The hypodiploid tumor had a single structural abnormality identified as a der(21)t(1;21)(q21;q22). The near-triploid tumor had numerous structural rearrangements, including a der(21)t(2;21)(q11;q22), which involves the same band of chromosome 21 as the translocation in the first tumor. Prophasing was a prominent cytogenetic feature of this tumor. The consistent involvement of band 21q22 in translocations in two chordomas suggests a possible specific association of this chromosome region with chordoma. Protooncogenes ETS2 and ERG have been mapped to this chromosome band.