A study report confirmed that 92% of benign/reactive cases were either CK20 (−) or (+) only in the upper 1/3 urothelium whereas in dysplastic cases CK20 staining distribution was noticed as 60% in 2/3 of the urothelium, 30% full thickness, 10% in the upper 1/3 urothelium and among carcinoma in situ (CIS) cases, 89% had full thickness of CK20 positivity [6]. This evidence concerns the gene KRT20 and in situ carcinoma.