Comparison of structural genetics of non-schistosoma-associated squamous cell carcinoma of the urinary bladder.

Little is known about genetic changes in squamous differentiation of non-schistosomiasis-associated bladder cancer. Therefore, we investigated pure squamous cell carcinomas (SqCC), squamous parts of mixed urothelial carcinomas with squamous differentiation (MIX) and mere urothelial cancers (UC) for structural genetic differences. Tissue microarray slides (n = 29 SqCC, n = 35 MIX and n = 23 UC) were analyzed by ZytoLight SPEC p16/CEN3/7/17 Quadruple Color Probe fluorescence-in-situ-hybridization (FISH) and DNA was investigated by comparative genomic hybridization (CGH) (n = 35 SqCCs, n = 40 MIX and n = 36 UC). By FISH the mean number of polysomic cells was lowest in SqCC (CEN3 P = 0.0498, CEN17 P = 0.0009). A slight tendency of lower copy numbers of chromosomes 3, 7 and 17 and higher numbers of the p16-locus in SqCC (P = 0.45) indicated less aneuploid tumor cells in SqCC compared to MIX and UC. In CGH SqCC showed the lowest mean number of aberrations per tumor (SqCC 5.37 changes, MIX 6.75 and UC 7.64; P = 0.1754). Significant differences between the three groups were found for loss of chromosome 3p (P = 0.004), 6q (P = 0.028), 11p (P = 0.024) and gains of 5p (P = 0.020). Loss of 3p was more frequent in SqCC (51.4%) than in MIX (37.5%) or UC (13.9%). To conclude, SqCCs show less polysomy and genetic alterations than MIX and UC. Loss of 3p is more frequent in SqCC but there are no absolute specific alterations for each tumor group. Squamous parts of mixed tumors show similar alterations than UC and should be considered as further development of UC, while pure SqCC seem to be a separate tumor group.