[WHO classification 2004: tumors of the kidneys].

New entities, confirmed either by cytogenetic findings or by new molecular markers, have been included in the WHO 2004 renal tumor classification. Moreover, imaging improvements provide a better radiologic description of tumors. In this article, we will discuss the WHO 2004 classification and focus on the new entities and their macroscopic appearance. We will especially insist on the following entities: multilocular clear cell renal carcinoma, Xp11 translocation carcinoma, low-grade mucinous tubular carcinoma, epithelioid angiomyolipoma, and benign mixed epithelial and stromal tumor. We also discuss the new concept of hybrid oncocytoma and chromophobe renal cell carcinoma, as well as the Birt-Hogg-Dube syndrome, which is associated with kidney tumors.