KRT20 and in situ carcinoma: Applying KRT20 and KRT5/6 protein expression as luminal and basal surrogate marker respectively, HR NMIBC patients with CIS were stratified into the three major CIS groups “luminal”, “null” and “mixed,” while the latter comprised four subgroups due to heterogenous inter-lesional marker expression in different CIS localizations of the same patients (Table 3, Fig. 1 and Online Resource 2).