A comparison between stereological estimates of mean nuclear volume and DNA flow cytometry in bladder tumours.

The correlation between stereological estimate of mean nuclear volume and DNA-content was studied in 55 human urinary bladder tumours. The DNA-content was determined by flow cytometry on isolated nuclei stained with ethidium bromide. Trout erythrocytes were used as a biological internal standard providing an accurate determination of the DNA-histogram. An unbiased estimate of the mean nuclear volume (vv) was obtained after standard formaline fixation, paraffin-embedding, sectioning and hematoxylin-eosin staining using the equation vv = pi/3.l3(0). Here l0 is the length of an intercept measured in a random direction through a test point, which hit a nucleus. A highly significant correlation was found between vv and mean DNA-content of nuclei (2p = 0.0004). A highly significant correlation was also found between vv and the highest DNA-content present in tumours having cell populations with different DNA content (2p = 0.0016). The mean nuclear volume and the DNA-content also correlated well with the pathologic grade. Although significant the correlations were far from perfect, which indicates that DNA content and mean nuclear volume may provide partly independent biological information. The methods provide objective, unbiased and reproducible data which may improve the possibility of grading and predicting the disease course of human urinary bladder tumours.