Flat intraepithelial lesions of the urinary bladder

BACKGROUND. In the 1998 World Health Organization and International Society of Urologic Pathology (WHO/ISUP) classification system for bladder neoplas ms, flat intraepithelial lesions of the urinary bladder were categorized as reactive atypia, atypia of unknown significance, dysplasia, and carcinoma in situ. The clinical outcomes of patients diagnosed with these atypical ur othelial proliferations are uncertain. METHODS. The authors studied a series of patients who were diagnosed with r eactive atypia of the urinary bladder (25 patients), urothelial atypia of u nknown significance (35), or urothelial dysplasia (26) between 1985 and 199 3. AU histologic slides were reviewed and classified according to the 1998 World Health Organization and International Society of Urologic Pathology c lassification system. Patients with a concomitant or prior history of carci noma in situ or urothelial carcinoma were excluded. RESULTS. Patient age at diagnosis ranged from 24 to 88 years (mean, 65 year s). The male-to-female ratio was 3:1. The mean follow-up was 3.9 years (ran ge, 0.1-13.4 years; median, 3.5 years). None of the patients with reactive atypia or atypia of unknown significance developed dysplasia, carcinoma in situ, or urothelial carcinoma. Four patients (15%) with urothelial dysplasi a developed biopsy-proven cancer, including 3 patients with muscle-invasive cancer. The mean interval from the diagnosis of urothelial dysplasia to th e development of cancer was 4.5 years. CONCLUSIONS, Patients with a diagnosis of urothelial atypia of unknown sign ificance or reactive atypia do not have adverse clinical outcomes, whereas patients with urothelial dysplasia of the bladder have an increased risk fo r the development of carcinoma in situ and urothelial carcinoma. (C) 2000 A merican Cancer Society.