Clonal telomeric fusions and chromosome instability in a subcutaneous sacrococcygeal myxopapillary ependymoma.

Subcutaneous sacrococcygeal myxopapillary ependymoma (SSME) is a very rare neurologic tumor with no demonstrable connection to the spinal column. Little is known of its etiology, clinical characteristics, or cytogenetics. Giemsa-band analysis revealed a stemline karyotype showing 62 chromosomes. Sidelines within the tumor showed clonal telomeric fusions resulting in dicentric chromosomes involving the fusion of numerous chromosomes. Recurrent telomeric fusions resulted in the progressive deletion of chromosome bands 11q25 and 11q23 and subsequently the entire long arm. This is the first case of a SSME to show clonal cytogenetic aberrations. However, of greater interest is the demonstration of the clonal progression of telomeric fusions resulting in dicentric chromosomes and the subsequent loss of chromosome arms. The observation of clonal telomeric breakage/fusion cycles as progenitor lesions to subsequent deletions provides evidence for telomeric association as an intermediate step in the progression of chromosomal instability.