Keratinising squamous metaplasia of the bladder: natural history and rationalization of management based on review of 54 years experience.

OBJECTIVE: To review our experience of keratinising squamous metaplasia of the bladder as a predictor for the development of cancer and other complications, and formulate a policy for its management.

MATERIALS AND METHODS: A retrospective review (1945-1999) identified 34 patients with histologically proven keratinising squamous metaplasia (27 males and 7 females, average age 50 years, range 13-80 years). The histological criteria used to diagnose keratinising squamous metaplasia were squamous metaplasia of the urothelium with keratinisation and/or hyperkeratosis and/or acanthosis. Female patients with non-keratinising squamous metaplasia (vaginal metaplasia) were excluded.

RESULTS: Four patients had synchronous bladder carcinoma (three advanced with early death; one localised, cured by cystectomy). Another 14 patients had extensive metaplasia (Group A, >50% of mucosal involvement). Three cases had cystectomy and cure. Six cases (out of 11) developed subsequent cancer (4 advanced and early death, two localised and cured by cystectomy). One other case died of obstructive uropathy secondary to squamous metaplasia. Two cases died of unrelated causes. Sixteen patients had limited squamous metaplasia (Group B, <50% involvement mucosal surface). Twelve patients had endoscopic resection, extraction bladder calculus etc. with no further complications. Another two patients underwent urinary diversion. Two patients (out of 16) developed subsequent cancer both with advanced disease and early death.

CONCLUSION: Keratinising squamous metaplasia of the bladder is a significant risk factor for vesical carcinoma and complications, such as bladder contracture and ureteral obstruction. This risk of complications increases with more extensive bladder mucosal involvement. The wide variation in lag time to the development of complications necessitates indefinite follow-up. Selected patients with extensive bladder involvement and long life expectancy should be offered cystectomy.