Chromosomal constitution of human spermatocytic seminomas: comparative genomic hybridization supported by conventional and interphase cytogenetics.

No data on the chromosomal constitution of spermatocytic seminomas are available thus far because of their rarity. Ploidy analysis performed on paraffin-embedded cases showed varying results from (near-) diploid to aneuploid. We applied comparative genomic hybridization on four snap-frozen primary spermatocytic seminomas of three different patients. Conventional cytogenetic analysis was successful in one, and "interphase cytogenetics" with centromeric region-specific probes was applied to another. The results from comparative genomic hybridization showed almost exclusively numerical chromosomal aberrations, in agreement with the data from karyotyping. Despite the limited number of cases studied, a nonrandom pattern of chromosome imbalances was detected: chromosome 9 was gained in all spermatocytic seminomas. This suggests that that this aberration plays a role in the development of this cancer. Interphase cytogenetics shows that the copy number of most chromosomes ranges from two to four, with an average of near trisomic. This constitutes the first report on the chromosomal constitution of spermatocytic seminomas.