The authors study nucleolar organisers (Ag NORS) in ten cases of uroth
elial tumours, graded as grade I in five cases, grade II in two cases,
grade III in two cases and intermediate grade II-III in one case. Stu
dy of the NOR index showed a mean value of 3.89 for grade 1, 4.66 for
grade II, 5.88 for grade III and 4.90 for the intermediate grade II-II
I. Different values were recorded in the same heterogeneous tumours co
ntaining tumour zones of different grades, providing an additional arg
ument in favour of the heterogeneity of these urothelial tumours and a
ccounting for the difficulties of their classification reported in the
literature. Adequate sampling should allow a more objective and more
representative study of all of the tumours examined.