Role of immunohistochemistry in diagnosing renal neoplasms when is it really useful?

Context.-With the refinement of molecular and histologic classifications of renal neoplasms and the availability of more-effective molecular targeted therapy for specific renal neoplasms, immunohistochemical techniques will play an increasingly important role in the diagnosis of renal neoplasm. During the past few decades, many markers have been evaluated for their role in the diagnosis, prognosis, and prediction of treatment for renal neoplasms. The number of useful markers in our routine practice continues to increase. The challenge will be to choose among them and to decide in which situations immunohistochemistry will be truly useful. Objectives.-To review the diagnostic utility of molecular markers for renal neoplasms and common diagnostic scenarios that call for immunohistochemistry in routine practice. Data Sources.-This review is based on published literature and personal experience. Conclusions.-Some of the most important and useful markers for the diagnosis of renal neoplasm include cytokeratins, vimentin, PAX2, PAX8, RCC marker, CD10, E-cadherin, kidney-specific cadherin, parvalbumin, claudin- 7, claudin-8, a-methylacyl coenzyme A racemase, CD117, TFE3, thrombomodulin, uroplakin III, p63, CD57, and carbonic anhydrase IX. Each marker has its diagnostic role in a specific diagnostic setting. The common diagnostic situations that call for immunohistochemical staining are differential diagnoses of renal versus nonrenal neoplasms, histologic subtyping of renal cell carcinoma, diagnosis of rare primary renal neoplasms, diagnosis of renal neoplasms in small core-biopsy specimens, diagnosis of possible metastatic renal carcinomas, and less frequently, molecular prognostication.