Renal cell tumours with papillary architecture: evolving concepts, classification and new emerging entities.

Renal cell carcinoma (RCC) with papillary architecture encompasses a diverse group of renal epithelial tumours. The entity papillary RCC is thought to be the second most common subtype of renal cell carcinoma. Although initially categorized into type 1 and type 2 subtypes based on histology, clinicopathological observations in conjunction with molecular advancements have reshaped the above categorization, suggesting that a significant number of the former type 2 tumours can be reclassified. This review traces the historical classification of papillary RCC, discusses emerging entities and reviews the recently recognized molecularly defined RCCs, highlighting diagnostic challenges, morphologic features and key immunohistochemical and genetic features.