TERT Promoter Mutations in Keratinizing and Nonkeratinizing Squamous Metaplasia of the Urinary Tract

We identified urothelial tract biopsy and resection specimens with keratinizing squamous metaplasia (KSM), nonkeratinizing squamous metaplasia (NKSM), and urothelial and squamous carcinomas over a 20-yr period, focusing on cases with neurogenic lower urinary tract dysfunction (NLUTD) and/or those with spatial or temporal variation in sampling. TERT promoter mutations as assessed via allele-specific polymerase chain reaction were surprisingly common in our testing cohort, identified not only in 15 (94%) invasive cancer foci but also in 13 (68%) examples of KSM and seven (70%) examples of NKSM. TERT promoter mutations were present in 23 foci from NLUTD specimens and 11 foci from bladder diverticula, including in foci of KSM, NKSM, and unremarkable urothelium from cases with no clinical association with previous, concurrent, or subsequent cancer. Our demonstration of temporally and spatially persistent TERT promoter mutation in examples of KSM and NKSM in cases of bladder cancer and in morphologically benign cases with neurogenic dysfunction suggests a molecular mechanism by which such pre-neoplastic lesions can potentially progress and develop into overt carcinoma. Given the interest in TERT promoter mutations as a potential biomarker for the development of bladder cancer, these findings possibly explain the association between conditions with chronic urinary bladder injury (such as the natural history of NLUTD) and higher risk of bladder cancer. TERT promoter mutations may represent an early event in bladder cancer tumorogenesis, and our findings expand on the clinical ramifications and predictive value of TERT promoter mutations in this context.

Mutations in the TERT gene are the most common genetic changes in bladder cancer. We found that these mutations are also sometimes present in patients with chronic bladder irritation such as neurogenic bladder dysfunction and changes to the lining of the bladder that pathologists would consider "benign." This finding might explain why such conditions are associated with the development of bladder cancer.