High levels of intratumor heterogeneity characterize the expression of epithelial-mesenchymal transition markers in high-grade clear cell renal cell carcinoma.

Immunohistochemistry is a basic routine in establishing the diagnosis of many tumors. However, immunomarkers are often irregularly distributed across different regions of the same tumor, alternating positive and negative areas without any apparent cause. Full identification of this type of intratumor heterogeneity is crucial for patients since the expression of many markers is linked to the prognosis and/or treatment of some tumors. We have quantified this variability testing 406 tumor samples from eight clear cell renal cell carcinomas using four epithelial-mesenchymal transition markers (vimentin, ZEB-1, β-catenin, and E-cadherin) and two different sampling protocols. Routine sampling included an amount of 59 samples (average, 7.3 samples/case) and multisite tumor sampling did a total of 347 samples (average, 43.3 samples/case). High variability of immunostaining was detected with E-cadherin and ZEB-1 in all high-grade cases. Irregular patterns of expression were detected in all tumors including all histologically homogeneous low-grade tumors. Multisite tumor sampling protocol detected a significant decreased number of E-cadherin, β-catenin and ZEB-1 positive samples in high-grade tumors. We conclude that high levels of intratumor heterogeneity characterize the immunohistochemical expression of epithelial-mesenchymal transition markers in high-grade clear cell renal cell carcinomas. Multisite tumor sampling protocol outperforms routine sampling in detecting immunohistochemical intratumor heterogeneity.