Immunohistochemistry of cytokeratin (CK) 5/6, CD44 and CK20 as prognostic biomarkers of non‐muscle‐invasive papillary upper tract urothelial carcinoma

Aims Immunohistochemical (IHC) staining for cytokeratin (CK) 5/6, CD44 and CK20 has been significantly associated with the prognosis of urinary bladder urothelial carcinoma, and probably reflects its molecular characteristics. We aimed to investigate the IHC‐based subgroups and their prognostic effects on non‐muscle‐invasive papillary upper tract urothelial carcinoma (UTUC). Methods and results IHC staining for CK5/6, CK20 and CD44 was analysed in 211 patients with non‐muscle‐invasive papillary UTUC. Staining was classified as showing a negative, positive or normal pattern. We found that CK5/6‐negative, CD44‐negative and CK20‐positive tumours were distinctly high‐risk subgroups that were associated with high grade (CK5/6‐negative, P