Chromosomal gains and losses in testicular germ cell tumors of adolescentsand adults investigated by a modified comparative genomic hybridization approach

Testicular germ cell tumors of adolescents and adults, both seminomas (SE) and nonseminomas (NS), are aneuploid, and classical karyotyping demonstrate d a specific pattern of gains and losses. More recently, these data have be en Supported by in situ hybridization and comparative genomic hybridization (CGH) on a limited number of samples. Interpretation of CGH results is com plicated by the intermediate ploidy of these tumors (3-4 n for SE and 2-3 n for NS). To circumvent this problem, this particular study was undertaken. CGH was performed on 8 SE and 10 NS, after which two single chromosome nor malizations were applied, one for chromosome 4 (found to be associated to t he lower ploidy level of the tumor) and one for chromosome 8 (found to be a ssociated with the higher ploidy level of the tumor). Using this modified C GH interpretation method, chromosomal regions with a similar copy number of chromosome 4 and 8 were identified as belonging to the lower and higher pl oidy level, and the regions below chromosome 4 and above chromosome 8 were identified as lost or gained outside the ploidy range of the tumor, respect ively. Our results are in accordance with earlier findings, however they ad d novel data, including comparison of SE and NS. This approach reveals rele vant information about the chromosomal constitution of testicular germ cell tumors, leading to a better understanding of the pathogenesis of these tum ors.