GROWTH FRACTIONS OF TRANSITIONAL CELL CARCINOMAS OF THE BLADDER DEFINED BY THE MONOCLONAL-ANTIBODY KI-67

We used an immunohistochemical technique with the monoclonal antibody Ki-67, which recognizes nuclear antigen expressed in proliferating cells to determine the growth fractions of 5 normal mucosa specimens and 55 transitional cell carcinomas of the bladder. Normal mucosa had a mean value of 0.37 ± 0.35% cells positive for Ki-67, whereas 9 histological grade 1 tumors showed 2.2 ± 1.5%, 31 grade 2 tumors averaged 10.1 ± 7.5% and 15 grade 3 tumors yielded 19.5 ± 9.0%. These values were significantly different from each other (p < 0.01), with Ki-67 indexes for grade 2 varying from 0.3 to 24.6%. Nonpapillary tumors had significantly higher indexes than papillary tumors (20.1 ± 8.0 versus 6.7 ± 5.9, p < 0.01). The Ki-67 indexes were 4.6 ± 4.5% for stage Ta (20 cases), 7.8 ± 4.7% for stage T1 (14) and 20.2 ± 7.8% for stages equal to or higher than T2 (21). Significant differences were noted between stages Ta and T1 (p < 0.05) and between stages T1 and T2 or greater (p < 0.01). Tumors with muscle layer invasion often showed more than 15% Ki-67 positive cells. Our results imply that Ki-67 indexes not only provide objective information to determine a malignant potential but also help to select the treatment.