Constitutive heterochromatin (C-banding) studies in patients with testicular malignancies.

The heterochromatic index [qh/(p + q) X 100] is a quantitative measure of variations in the heterochromatic regions of C-banded cells which minimizes differential contraction of heterochromatic and euchromatic areas. Heterochromatic indices of the homologues of chromosomes #1, #9, #16, and Y were studied in the genotypes of 48 patients with germinal tumors and in 30 controls. The heterochromatic indices of chromosome #9 in patients showed statistically significant heteromorphism compared with controls. In addition, the heteromorphism was found to increase from the lower malignancy seminoma to the highly malignant teratoma. A similar but statistically nonsignificant pattern was seen in chromosome #16. No statistical difference in the mean of the heterochromatic indices was found in chromosomes #1 and Y. The difference in the mean heterochromatic index in chromosome #9 appeared to be due to an increase in the mean heterochromatic index in chromosome #9 appeared to be due to an increase in the amount of constitutive heterochromatin and not to a decrease.