Renal Cell Tumors: Understanding Their Molecular Pathological Epidemiology and the 2016 WHO Classification

Abstract

Accumulating evidence suggests that renal cell tumors represent a group of histologically and molecularly heterogeneous diseases, even within the same histological subtype. In accordance with the increased understanding of the morphological, immunohistochemical, molecular, and epidemiological characteristics of renal cell tumors, the World Health Organization (WHO) classification of renal cell tumors has been modified. This review provides perspectives on both new and current subtypes of renal cell tumors, as well as on the emerging/provisional renal cell carcinomas in the new 2016 WHO classification, which focuses on features of their molecular pathological epidemiology. The WHO classification will require additional revisions to enable the classification of renal cell tumors as clinically meaningful subtypes and provide a better understanding of the unique characteristics of renal cell tumors.

Keywords: genetic alteration; histology; immunohistochemistry; kidney; molecular pathology; renal cell carcinoma.

Figure 1

Morphology of the major subtypes of renal cell carcinoma (RCC) (hematoxylin and eosin staining; scale bar, 100 µm). (A) Clear cell RCC; (B) papillary RCC; and (C) chromophobe RCC. Clear cell RCC typically consists of clear cells with thin-walled, staghorn-shaped vasculature (A). Papillary RCC is typically composed of papillae formed by fibrovascular cores that often contain foamy macrophages (B). Chromophobe RCC typically contains a mixture of eosinophilic and clear cells with voluminous cytoplasm, perinuclear clearance, and well-defined cell borders, displaying a solid, sheet-like pattern (C).