ObjectiveTo investigate the impact of grading in urothelial bladder cancer (UBC) stages Ta and T1, comparing the World Health Organization (WHO) grading classifications of 1973 (WHO73) and 2004 (WHO04) and a combination of these (WHO73/04).Patients and MethodsAll patients with primary Ta and T1 UBC in the ostergotland region, Sweden, between 1992 and 2007 were included. From 1992, we introduced a new programme for management and follow-up of UBC, including prospectively performed registration of all patients, a systematic description of the location and size of all tumours, primary resection and intravesical treatment in the case of recurrence. All tumour specimens were retrospectively reviewed in 2008 and graded according to the WHO73 and WHO04. A combination of WHO73/04, Grade 1 (G1), Grade 2 low grade (G2LG), Grade 2 high grade (G2HG) and Grade 3 (G3) was analysed in relation to clinical variables and outcomes.ResultsThere were 769 patients with a median age of 72 years and a median follow-up duration of 74 months. Recurrence was noted in 484 patients (63%) and progression in 80 patients (10%). Recurrence was more common in multiple tumours, larger tumours and in tumours of higher grade (G2LG, G2HG and G3). Progression was more common in tumours classified as larger, T1 and G2HG and G3. Notably, in tumours classified as G2HG, recurrence and progression were more common than in the G2LG group. Harrells concordance index for the WHO73/04 was higher for recurrence and progression than in the WHO73 or WHO04.ConclusionIn the four-tier combined WHO73/04 for urothelial cancer, we observed two G2 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 had greater accuracy for recurrence and progression than either the WHO73 or WHO04.