P53 overexpression in bladder urothelial neoplasms: new aspect of World Health Organization/International Society of Urological Pathology classification.

INTRODUCTION The aim of this study was to investigate the probable differences in P53 expression between papillary urothelial neoplasm of low malignant potential (PUNLMP) and varying grades of transitional cell carcinoma (TCC) of the bladder. MATERIALS AND METHODS Ten biopsy specimens of the patients with PUNLMP, 20 of the patients with papillary low-grade TCC, 20 of those with invasive high-grade TCC, and 10 of healthy individuals were stained for P53 protein by immunohitochemical methods. Histological grading was performed according to the World Health Organization/International Society of Urological Pathology consensus classification of urothelial neoplasms of the urinary bladder. RESULTS Nuclear P53 protein in invasive high-grade TCC was slightly more frequent than that in noninvasive low-grade papillary TCC (P = .35). Ten percent of specimens with PUNLMP had nuclear P53 accumulation, while in low-grade and high-grade TCCs, 75% and 85% of the specimens were positive for P53 protein accumulation (P < .001). Expression of P53 was nil in all normal transitional epithelium specimens. CONCLUSION Overexpression of P53 in papillary low-grade TCC and invasive high-grade TCC, while lacking of expression in PUNLMP indicates that mutations of P53 gene are not usually associated with the development of urothelial neoplasms and they may play a crucial role only in progression of PUNLMP to low-grade TCC.