A new WHO classification of renal cell carcinoma has been introduced in 2004. This classification includes the recently described renal cell carcinomas with the ASPL-TFE3 gene fusion and carcinomas with a PRCC-TFE3 gene fusion. Collectively, these tumors have been termed Xp11.2 or TFE3 translocation carcinomas, which primarily occur in children and young adults. To further study the characteristics of renal cell carcinoma in young patients and to determine their genetic background, 41 renal cell carcinomas of patients younger than 22 years were morphologically and genetically characterized. Loss of heterozygosity analysis of the von Hippel-Lindau gene region and screening for VHL gene mutations by direct sequencing were performed in 20 tumors. TFE3 protein overexpression, which correlates with the presence of a TFE3 gene fusion, was assessed by immunohistochemistry. Applying the new WHO classification for renal cell carcinoma, there were 6 clear cell (15%), 9 papillary (22%), 2 chromophobe, and 2 collecting duct carcinomas. Eight carcinomas showed translocation carcinoma morphology (20%). One carcinoma occurred 4 years after a neuroblastoma. Thirteen tumors could not be assigned to types specified by the new WHO classification: 10 were grouped as unclassified (24%), including a unique renal cell carcinoma with prominently vacuolated cytoplasm and WT1 expression. Three carcinomas occurred in combination with nephroblastoma. Molecular analysis revealed deletions at 3p25-26 in one translocation carcinoma, one chromophobe renal cell carcinoma, and one papillary renal cell carcinoma. There were no VHL mutations. Nuclear TFE3 overexpression was detected in 6 renal cell carcinomas, all of which showed areas with voluminous cytoplasm and foci of papillary architecture, consistent with a translocation carcinoma phenotype. The large proportion of TFE3 "translocation" carcinomas and "unclassified" carcinomas in the first two decades of life demonstrates that renal cell carcinomas in young patients contain genetically and phenotypically distinct tumors with further potential for novel renal cell carcinoma subtypes. The far lower frequency of clear cell carcinomas and VHL alterations compared with adults suggests that renal cell carcinomas in young patients have a unique genetic background.

Purpose: Morphologic intratumor heterogeneity is well known to exist in hepatocellular carcinoma (HCC), but very few systematic analyses of this phenomenon have been performed. The aim of this study was to comprehensively characterize morphologic intratumor heterogeneity in HCC. Also, taken into account were well-known immunohistochemical markers and molecular changes in liver cells that are considered in proposed classifications of liver cell neoplasms or discussed as molecular therapeutic targets.Experimental Design: In HCC of 23 patients without medical pretreatment, a total of 120 tumor areas were defined. Analyzed were cell and tissue morphology, expression of the liver cell markers cytokeratin (CK)7, CD44, a-fetoprotein (AFP), epithelial cell adhesion molecule (EpCAM), and glutamine synthetase (GS) along with mutations of TP53 and CTNNB1, assayed by both Sanger and next-generation sequencing.Results: Overall, intratumor heterogeneity was detectable in the majority of HCC cases (20 of 23, 87%). Heterogeneity solely on the level of morphology was found in 6 of 23 cases (26%), morphologic heterogeneity combined with immunohistochemical heterogeneity in 9 of 23 cases (39%), and heterogeneity with respect to morphologic, immunohistochemical, and mutational status of TP53 and CTNNB1 in 5 of 23 cases (22%).Conclusions: Our findings demonstrate that intratumor heterogeneity represents a challenge for the establishment of a robust HCC classification and may contribute to treatment failure and drug resistance in many cases of HCC.

Mutations of the von Hippel-Lindau (VHL) gene are considered critical for the initiation of clear cell renal cell carcinoma. The VHL protein is involved in regulation of the cell cycle and neo-vascularization. In this study, the association of VHL mutations with tumour cell proliferation, angiogenesis, and clinical outcome was analysed in 113 clear cell renal cell carcinomas. The degree of angiogenesis and tumour cell proliferation was immunohistochemically determined by counting microvessels (microvessel density, anti-CD34 antibody) and cells with proliferating activity (Ki-67 labelling index, MIB-1 antibody). Forty-eight different VHL sequence alterations were found in 38 of 113 patients (34%) by direct sequencing. Nineteen VHL mutations were frameshifts and nonsense mutations, predicted to change the open reading frame of VHL. These 'loss-of-function' mutations correlated with worse prognosis in univariate analysis (p=0.02). Tumour grade, stage, microvessel density, and tumour cell proliferation were not associated with VHL alterations. These findings may indicate that 'loss-of-function' VHL mutations are involved in the progression of a clear cell renal cell carcinoma subset, whereas regulation of angiogenesis and proliferation of renal carcinoma in vivo is apparently not directly influenced by VHL alterations.

Renal cysts and clear cell renal cell carcinoma are common clinical manifestations of people with germ-line mutations of the von Hippel-Lindau tumor suppressor gene, VHL. Recent cell biological evidence suggests that the VHL gene product, pVHL, functions to maintain the primary cilium, a microtubule-based antenna-like structure whose functional integrity is believed to have an important role in cell-cycle control. As VHL mutations are common in sporadic clear cell renal cell carcinoma, but not papillary renal cell carcinoma, we asked whether there is an association between VHL status and primary cilia in vivo. VHL status was assessed in 20 cases of clear cell renal cell carcinoma and 9 cases of papillary renal cell carcinoma by DNA sequencing and by immunohistochemical staining for the hypoxia-inducible factor-a target gene products CA9 and GLUT-1. Of 20, 18 clear cell renal cell carcinomas, but only 1 of 9 papillary renal cell carcinomas, displayed evidence of VHL inactivation. In clear cell renal cell carcinoma the frequency of ciliated tumor cells ranged from 0 to 22% (median value 7.8±6.0%), whereas cilia frequency was significantly higher (Po0.0001) in papillary renal cell carcinoma (range 12-83%, median value 43.3 ± 21.3%). There was no correlation between Ki-67 staining and cilia frequency, suggesting that the observed differences between the tumor types in cilia frequency are not accounted for by differences in cellular proliferation rates and that primary cilia degeneration in sporadic clear cell renal cell carcinoma depends on VHL inactivation. We propose that the different ciliation status of clear cell and papillary renal cell carcinoma may contribute, at least in part, to the different biological behaviors of these tumor types.

The chromosomal region 12q13-q15 is recurrently ampli®ed in bladder cancer. Putative target genes located in this region include MDM2, CDK4, and GLI. To evaluate the involvement of these genes in bladder cancer, we screened a tissue microarray (TMA) containing 2317 samples by¯uorescence in situ hybridization (FISH). Ampli®cation was found for MDM2 in 5.1%, for CDK4 in 1.1%, and for GLI in 0.4% of interpretable tumors. Among tumors having ampli®cation of at least one of these 12q13-q15 genes, 76.6% had ampli®cation of MDM2 alone and 6.4% had ampli®cation of CDK4 alone. Coampli®cations were seen of MDM2 and CDK4 in 10.6%, and of CDK4 and GLI in 6.4%. Neither coampli®cations of all three genes nor isolated GLI ampli®cations were found. These data suggest a prominent role of MDM2 as a 12q13-q15 ampli®cation target in bladder cancer. However, independent CDK4 ampli®cations do also occur suggesting either two nonoverlapping ampli®cation sites or else a minimal overlapping region between MDM2 and CDK4 perhaps containing another yet unknown oncogene. The frequency of ampli®cation increased signi®cantly from stage pTa to pT1-4 (P50.04) and from low to high grade (P50.005). These data are consistent with a high level of genetic instability in invasively growing and highgrade bladder tumors.