[FISH analysis in the differential diagnosis of flat urothelial lesions using tissue microarrays]

FISH technology offers an additional tool in the diagnosis of precancerous and malignant lesions of the urinary tract from cytological specimens. Here, we examined the relevance of chromosomal imbalance in flat urothelial lesions using FISH on paraffin-embedded tissue. In addition, the status of Her2/neu and STK15, a key molecule in the development of aneuploidy, was evaluated.

Flat lesions (normal urothelium, hyperplasia, reactive atypia, dysplasia and Carcinoma in situlCis) of 73 patients were analyzed in respect of chromosome 3, 7, 17 polysomy, deletion of p16, status of HER2/neu and of STK15 by FISH (UroVysion, PathVysion, Vysis) and immunohistochemistry (HercepTest, DAKO) using tissue microarrays. The data were correlated with histology.

Aneusomy of at least one of the chromosomes usually correlates with the histology of carcinoma in situ or invasive tumor growth. Reactive atypias, rarely showing chromosomal imbalance, can be distinguished from Cis in the majority of investigated cases, but the FISH technique is not able to differentiate reactive atypia from mild dysplasia. About 30 % of the non-neoplastic lesions like urothelial hyperplasia and normal urothelium display polysomy of at least one chromosome in more than 20% of all cells, indicating an elevated risk towards a synchronous development of a higher dysplastic lesion (i.e. Cis). Polysomy of one of three investigated chromosomes (3, 7, 17) occurs randomly within all lesions. A deletion of the p16 locus is most frequently observed in aneuploid lesions. Altered Her2/neu expression patterns are frequently observed in malignant and dysplastic lesions but also in 25 % of the non-neoplastic lesions. An overexpression of Her2/ neu is found in 10-20% of invasive urothelial carcinomas and occasionally in Cis (5 %). However, the Her2/neu gene locus is not amplified in these samples. Gene amplification of STK15 was seen in tumors as well as in normal urothelium but it is still unclear whether it indicates an elevated risk towards the development of manifest urothelial tumors.