High resolution chromosome banding in search of germ line mutations applied on testicular cancer patients.

Patients with bilateral and/or familial testicular cancer are assumed to demonstrate germ line mutations if such mutations are instrumental in testicular cancer patients. Constitutional rearrangements have to our knowledge not been reported, while an increased level of constitutional chromosome instability has been claimed. Lymphocytes from 12 Norwegian patients with bilateral or familial testicular cancer have been studied by high resolution Giemsa banding. A possible germ line mutation would be expected to be seen in every cell. It is therefore sufficient to examine one pair of the individual chromosomes obtained, if necessary, from several cells. Based on our previous findings of loss of heterozygosity in the chromosome regions 3p and 11p in testicular tumors, these chromosome arms were paid special attention. However, no mutations were observed in these regions nor in any other chromosome. Applying a 95% confidence interval, we conclude that less than 23% of familial and/or bilateral testicular cancer patients are caused by germ line mutations large enough to be detected with high resolution banding of at least 450 G-bands per haploid genome. The presented analyses were used to standardize the resolution determination in our laboratory.