Ancillary Studies Applied to Renal Masses

Renal cell carcinoma (RCC) and, in general, kidney tumors are a cluster of histopathological and molecular heterogeneous lesions, with different sets of genetic and epigenetic abnormalities, as well as clinical behavior and therapeutic response. Therefore, ancillary testing must be used wisely and appropriately for the main differential diagnoses in an individualized fashion. Having said that, the landscape of the immunohistochemical studies with a description of common markers and patterns, as well as main clusters of tumors, is essential to better understand these neoplasms in order to reach the correct diagnosis. Immunohistochemistry (IHC) is a valuable tool for proper diagnostic, prognostic, and predictive evaluation, since treatment is often decided based on tumor type. Although histologic assessment and IHC remain the foundation of renal biopsy interpretation, cytogenetic and molecular characterizations of renal neoplasms have been increasingly employed in the clinical setting to help improve histologic classification and guide management decisions when histology and immunohistochemistry profiles do not provide a clear diagnosis. This chapter’s aim is to discuss practical utilization of ancillary testing, describing best immunohistochemistry usage and exploring cytogenetic and molecular advances in this field