Bladder cancer grading using the four-tier combination of the WHO 1973 and WHO 2004 classifications.

In the four-tier combined WHO73/04 classification for urothelial cancer, we observed two grade 2 sub-groups, G2HG and G2LG. There was a better outcome in the latter group, and the importance of G1 and G3 tumours could be fully evaluated. The WHO73/04 classification has higher accuracy for recurrence and progression than either the WHO73 or the WHO04 classification.