A recent study initiated by the University of Toronto, Canada, showed that the WHO 1973 and 2004 bladder tumor grading systems alone are not significantly superior in predicting tumor recurrence. The investigators reviewed 325 biopsy specimens of patients with non-muscle invasive bladder cancer from three different general hospitals and evaluated them using the WHO 1973 (grade 1 G1, grade 2 G2, grade 3 G3) and 2004 versions (low grade malignant potential uroepithelial papillary tumor PULMP, low grade LG, high grade HG) grading systems, respectively, and found that both were comparable in predicting bladder cancer progression comparable strengths, but no significant advantage for predicting bladder tumor recurrence. The investigators concluded that integration into a four-grade grading system (low-grade (PULMP/LG/G1), mid-grade (LG/G2), and high-grade (HG/G3)) could predict both bladder tumor progression and recurrence. (Mod Pathol. 2014 Nov 28)