Transition of organizational category on renal cancer.

The incidence of kidney cancer is gradually increasing, with a rate of 2-3% per decade. The kidney develops various kinds of neoplasms, some of which are associated with familial cancer syndromes. Such cases have provided clues to identify the cancer-responsible genes. In 2004, the World Health Organization published a new classification system of renal neoplasms, incorporating recent knowledge obtained in the cytogenetic and molecular biological fields, i.e. genes responsible for each histologic subtype (von Hippel-Lindau for clear cell renal cell carcinoma, c-met for papillary renal cell carcinoma type 1, etc.). Subsequently, the Japanese classification system in 'the General Rule for Clinicopathological Study of Renal Cell Carcinoma' has been revised as the 4th edition, according to the World Health Organization system. Several novel subtypes have been introduced, i.e. mucinous tubular and spindle cell carcinoma, and Xp11.2/TFE3 translocation-associated renal cell carcinoma. Even after the publication of the classification, other novel subtypes have emerged, i.e. acquired cystic disease-associated renal cell carcinoma and tubulocystic renal cell carcinoma. Additionally, some of the subtypes seem to form families based on morphological transition, immunohistochemical features and gene expression profile. In future, the classification of renal cell carcinoma should be reorganized on the basis of molecular biological characteristics to establish personalized therapeutic strategies.