Biopsy of apparently normal urothelium in patients with bladder carcinoma.

We obtained 246 cold cup biopsies from pre-selected sites of apparently non-tumor-bearing bladder urothelium from 82 patients who presented with bladder cancer for the first time. Of 75 patients with transitional cell carcinoma 32 (43 per cent) suffered coincidental urothelial abnormalities, the most common being atypia. Significant abnormalities occurred more commonly (77 per cent) in association with high grade tumors than with low grade tumors (15 per cent).