Keratinizing squamous metaplasia of the bladder: a review

Keratinizing squamous metaplasia is infrequently found in bladder biopsies and its clinical significance remains unclear, with studies linking it to the development of invasive squamous cell carcinoma. Once diagnosed, there is a dilemma how to treat and follow-up this group.

We reviewed the literature on the topic with particular emphasis on natural history, management and subsequent follow-up.

Keratinizing squamous metaplasia of the bladder is rare. Pathognomonic findings on biopsy are required to confirm the diagnosis. Both synchronous diagnosis of urothelial tumour and subsequent tumour development on follow-up has been identified. Risk of malignant transformation increases in the presence of dysplasia as well as with extensive keratinization. Lesions should be treated with local transurethral resection. Considering the lack of evidence cystectomy cannot be justified for those with extensive lesions.

Currently there is not enough data to identify keratinizing squamous metaplasia of the bladder as a pre-malignant condition; this term being reserved for those with obvious histological dysplasia. However at present all patients should undergo regular follow-up.