Cytophotometric characterization of the WHO grades of transitional cell neoplasms.

The WHO classification of urothelial bladder tumours is widely used, but does not seem to be entirely satisfactory. The main problem is the unhomogeneous WHO II group, and borderline cases in particular are difficult to evaluate histopathologically. Objective assessment of atypia would allow more reliable correlation between morphology and biological behaviour of the tumours to be made. We describe measurements of atypia in 3 characteristic cases of papillary bladder tumour of each WHO grade I, II, and III using Feulgen-DNA-cytophotometry. The mean optical density and nuclear area is determined in 5 micron thick tissue sections. The optical density and nuclear area for each specimen are plotted in a scatter diagram, and the position and variability of the cluster are evaluated. Cytophotometric characterization resulted in defined groups of WHO-graded tumours, and due to this encouraging result the method will be applied in a more comprehensive study of WHO II carcinomas.