Identification of isochromosome 1q as a recurring chromosome aberration in skull base chordomas: a new marker for aggressive tumors?
Chordomas are locally invasive bone tumors that appear in adulthood and are thought to originate from the remnants of the notochord. Because chordomas have a predilection for the ends of the spinal column, most lesions are found in the sacrococcygeal region and the base of the skull. 7, 16, 17 Approximately 35% of chordomas arise at the base of the skull, approximately 50% arise in the sacrococcygeal region, and the remaining 15% are found in the vertebral bodies. 14 Skull based chordomas are
... sed chordomas are slowgrowing tumors and, in many cases, are associated with a significant amount of bone and soft-tissue destruction. Metastasis can occur but usually in the late stages of tumor progression. Because of their location, cranial chordomas are difficult to manage and gross-total resection is not always possible; therefore the recurrence rate is high. 14 Unfortunately, the prognosis for patients with intracranial tumors is poor, as the progression of the tumor causes death in most patients. 12 Cytogenetic studies of chordomas are limited. The great majority of cases reported are lumbosacral chordomas, which have shown diverse chromosome aberrations. 2,3,6,8, Object. The authors conducted a study of 22 skull base chordomas. Methods. A series of 22 skull base chordomas was analyzed with G banding. Subsequently, metaphase cells obtained from three tumors were reexamined using multicolor spectral karyotyping. Clonal chromosome aberrations were identified in 11 cases, all of which were recurrent tumors. Three tumors showed a remarkable similarity in cytogenetic features, and these features appear to characterize a recurring combination of nonrandom chromosome aberrations, including isochromosome 1q, gain of chromosome 7, and monosomy for chromosomes 3, 4, 10,13, and 18. Isochromosome 1q was identified as the sole recurring structural chromosome rearrangement in these tumors. The pattern of chromosome loss reported in the progression of lumbosacral chordoma also appears to be true of skull base chordomas with the additional findings of isochromosome 1q, gain of chromosome 7, and loss of chromosome 18. Conclusions. Skull base chordomas characterized by isochromosome 1q and monosomy 13 provide support for the concept of the loss of putative tumor suppressor loci on 1p and 13q and aggressive tumor behavior. KEY WORDS • chordoma • chromosome aberration • isochromosome 1q • spectral karyotyping • cytogenetics Neurosurg. Focus / Volume 10 / March, 2001 1 Abbreviations used in this paper: DAIP = 4,6-diamidino-2phenylidole; LOH = loss of heterozygosity; RB = retinoblastoma; SKY = spectral karyotyping.