Detection of genetic instability and proliferative activity in urinary bladder intraepithelial flat lesions using UroVysion fluorescence in-situ hybridization and flow cytometry

Abstract

Background Chromosomal abnormalities play a key role in neoplastic potential for flat urothelial lesions, irrespective of whether cytologic atypia is present or not. Having information about lesions with malignant potential in the urinary bladder can help clinicians in taking logical actions concerning management after urinary bladder-conserving resections.Aim The aim of the study was to differentiate various flat urothelial lesions by detecting its genetic abnormalities and proliferative activity using UroVysion fluorescence in-situ hybridization and flow cytometry.Patients and methods Ninety-eight paraffin-embedded tissue sections from 35 patients with infiltrative bladder cancer and flat urothelial lesions [reactive atypia, hyperplasia, dysplasia, carcinoma in situ (CIS), squamous metaplasia, glandular metaplasia, histologically normal urothelium in patients with tumor and control] were assessed by flow cytometry and fluorescence in-situ hybridization using UroVysion targeted against the band 9p21 locus and pericentromeric areas of chromosomes 3, 7, and 17.Results Gain of at least one of the chromosomes was observed in 60% of samples being more than 90% in CIS, dysplasia, and infiltrating bladder tumors. The mean percentage of cells with polysomy in reactive atypia, flat urothelial hyperplasia, glandular metaplasia, keratinizing squamous metaplasia, and histologically normal urothelium in patients with tumors ranged from 12 to 20%, but in CIS and dysplasia it was 67 and 44%, respectively. Deletion of the P16 locus was detected in 49% of lesions. Flow cytometry displayed aneuploidy pattern in 60% of lesions with higher percentage in CIS, dysplasia, and infiltrating bladder tumors. High S-phase fraction (SPF) was observed in 44% of samples. High S phase showed significant association with polysomy and DNA ploidy (P=0.02 and 0.01, respectively). In addition, there was association between polysomy expression with del 9p21 (P=0.03) and between del 9p21 with DNA ploidy and SPF (P=0.003 and 0.02).Conclusions Our analysis has shown that combined evaluation of flat urothelial lesions using UroVysion, DNA ploidy, and SPF help in the recognition of these lesions, especially those with higher genetic abnormalities and having higher S phase because follow up of these lesions showed a higher tendency for malignant transformation. Furthermore, estimation of continuing chromosomal instability such as polysomy, DNA aneuploidy, and high SPF might deliver further interpretation of urinary bladder cancer risk assessment away from the position and histopathology of precancerous lesions.