Intratumoural heterogeneity of nuclear DNA-content and proliferation in clear cell type carcinomas of the kidney.

Clear celled renal carcinomas (n = 37) were investigated by flow cytometry for intratumoural heterogeneity in DNA-ploidy and proliferation (S-phase rate). Using gross sections of the tumours, 178 regions of interest were selected and excised from the paraffin blocks. Of the tumours examined 30% (n = 11) were DNA-diploid and 70% (n = 26) were DNA-aneuploid. In six tumours (16%) homogenous DNA-aneuploidy was detected, and in 20 others (54%) there was intratumoural heterogeneity of DNA-content with a blend of either DNA-diploid and DNA-aneuploid regions (n = 16; 43%) or different aneuploid stemlines (n = 4; 11%). DNA-aneuploidy was present both in areas of the tumours composed of clear cells and in regions containing cells with cytoplasmatic eosinophilia. However, DNA-aneuploidy was correlated in a statistically highly significant manner with the degree of cytoplasmatic eosinophilia and the nuclear grading of tumour cells. The results were confirmed by comparative analysis of fresh-frozen and paraffin-embedded material. The DNA-aneuploid portions of the tumours, and the regions with increased cytoplasmatic eosinophilia, proved to have significantly higher S-phase rates than DNA-diploid and clear tumour cells. These results agreed well with the immunohistochemically determined percentage of Ki-67 (proliferation associated)-antigen positive cells. Our findings indicate that tumour cells with increased eosinophilia in renal cell carcinomas are distinct from real clear cells by virtue of their higher rates of aneuploidy and proliferative activity. These cells might therefore be regarded as a subclass with a more aggressive biological behaviour.