Validation of Keratin 17 as a Tissue Biomarker in the Diagnosis of Upper Tract Urothelial Carcinoma.

Upper tract urothelial carcinoma (UTUC) has a relatively low incidence but presents significant surveillance and treatment challenges. Therefore, novel biomarkers for the accurate detection of upper tract urothelial tumors are urgently needed. We evaluated the expression of Keratin 17 (KRT17), an oncoprotein implicated in the cell cycle progression of multiple human cancers and previously studied in bladder urothelial carcinoma, by immunohistochemistry in 139 UTUC cases, including noninvasive, invasive papillary urothelial carcinoma and urothelial carcinoma in situ. KRT17 expression pattern (basal/negative vs. nonbasal) and H-score were evaluated. The expression pattern was significantly different in normal (NL) compared to malignant urothelium. Nonbasal KRT17 expression was significantly higher in pTa (p<0.001) and invasive (pTinv) (p=0.0023) urothelial carcinoma compared to NL, and in pTinv compared to pTa (p=0.0391). Sensitivity and specificity for distinguishing benign from malignant tumors were 85% and 82, respectively, with an area under the curve of 0.83 (p <0.001). The KRT17 H-score was significantly higher in pTa and pTinv compared to NL (p < 0.001 and p=0.0035, respectively). Sensitivity and specificity for distinguishing benign from malignant carcinoma were 91% and 69%, respectively, with an AUC of 0.81 (p=0.0010). KRT17 was not associated with tumor site, grade, or stage. In summary, K17 is a sensitive and specific marker of neoplastic upper tract urothelium, and its potential use in routine diagnostics should be explored in larger studies.