Nuclear size and chromatin concentration in transitional cell carcinoma of the human urinary bladder.

Feulgen-stained cell nuclei from 25 specimens from transitional cell carcinoma of the human bladder were examined by means of cytophotometric scanning measurements. The mean values of nuclear area, DNA-content and chromatin concentration after scanning of a hundred nuclei per specimen were compared with those from a control group consisting of 10 specimens of normal transitional cell epithelium. Within the same ploidy class the more differentiated carcinoma cells showed nuclear enlargement and decrease of mean chromatin concentration. Undifferentiated tumours could have the same or higher mean chromatin concentration as the control group owing to the many highpolyploid nuclei. Undifferentiated tumours contained numerous giant nuclei, whereas these were rare in well differentiated carcinoma. When allowances were made for variations due to fixation and staining measurement of the nuclear area could serve as means of differentiating between normal and cancer nuclei with a high degree of statistic probability. The question whether nuclear enlargement and decreased chromatin concentration represent physiological changes or are entirely or partly the result of chemical carcinogenesis is discussed.