Clinicopathologic And Molecular Genetic Study Of Renal Cell Carcinomas Occurring In Teenagers

BACKGROUND AND OBJECTIVE:Juvenile RCCs are relatively rare and represent approximately 2-6% of all renal neoplasm in children and young adults. Molecular and cytogenetic studies of juvenile RCCs, sporadic or hereditary, have revealed multiple associated abnormalities. Hereditary RCCs are often associated with VHL disease which display multiple germline mutations and deletions in the VHL gene on 3p25. In this disease, RCC usually shows a similar morphologic appearance as conventional (clear cell) RCC. Recently, the mutations of VHL gene were also found in sporadic papillary RCC, chromophobe RCC, oncocytoma, and Xp11.2 translocation RCC. Most cases of juvenile RCC are sporadic and associated with Xp11.2 translocations/TFE3 gene fusions which are characterized by a number of different translocations involving Xp11.2 chromosome, all of them resulting in gene fusions with the TFE3 gene. The two most common forms are the t(X;17)(p11.2;q25) translocation with ASPL-TFE3 fusion and the t(X;1)(p11.2;q21) translocation with PRCC-TFE3 fusion. In addition, two recent multicenter studies demonstrated that targeted therapy [vascular endothelial growth factor receptor (VEGFR)-targeted agents and/or mammalian target of rapamycin (mTOR) inhibitors] can be of benefit in patients with Xp11.2 translocation RCC. It is obvious that the distinction between Xp11.2 translocation RCC and other subtypes of renal tumors is clinically important. A recently developed antibody of TFE3 protein has been shown to be highly sensitive and specific markers in the kind of translocation carcinoma. However, it can give discrepant results in different laboratories mainly due to many technical factors, such as fixation time and method, antigen retrival, the scoring system, and antibody specificity and sensitivity. Although juvenile RCCs were recognized as a distinct pathologic entity from adult RCCs, there have been relatively few published reports of them. The prognosis for juvenile RCCs remains unclear. We, therefore, retrospectively analyzed 51 consecutive cases of pediatric RCCs. The purposes of this study were (1) to delineate further the clinical, morphological, and immunohistochemical features; (2) to detect the prevalence of VHL alterations in RCCs of young patients; (3) to develop a fluorescence in situ hybridization (FISH) assay to serve as an alternative diagnostic tool using the most accessible material in the lab, formalin-fixed, paraffin-embedded (FFPE) tissues, for the detection of TFE3 (Xp11.2) gene rearrangement; (4) to better define the biological features of pediatric RCCs and determine whether clinical outcome of TFE+juvenile RCCs differed from TFE-RCCs in this age group.MATERIALS AND METHODS:51 RCCs of patients younger than 25 years were morphologically and immunohistochemically characterized with follow-up. Loss of heterozygosity (LOH) analysis of the von Hippel-Lindau (VHL) gene region and screening for VHL gene mutations were analyzed in all cases. RT-PCR was performed in 3 cases for detecting fusion gene. A FISH assay was developed to detect TFE3 gene rearrangement. We also performed a systematic review and meta-analysis to better define the biological features of juvenile RCCs.RESULTS:Applying the 2004 WHO classification for RCC, there were 24 Xp11.2 translocation RCCs,9 clear cell RCCs,17 papillary RCCs, and 1 unclassified RCC. Except 1 case, all 23 Xp11.2 translocation RCCs showed immunoreactivity for TFE3. None had TFEB immunoreactivity. Eight types of histological patterns of Xp11.2 translocation RCCs were observed. Nine tumors (cases 1 to 8, and case 9 a molecularly confirmed ASPL-TFE3 RCC) presented a nested to papillary architecture with extensive psammoma bodies corresponded to the typical morphology of t(X; 17) ASPL-TFE3 phenotype. Six tumors (cases 10 to 15) had morphologic features more consistent with the t(X;1) PRCC-TFE3 phenotype. In cases 16 to 19, the tumors were present as nested or alveolar pattern with foci of papillary architecture, and composed of cells with clear cytoplasm, uniform round and low-grade nuclei, and inconspicuous nucleoli, mimicking clear cell RCC. Interestingly, several of the carcinomas demonstrated uncommon morphologic features. Case 20 contained neoplastic cells arranged in a papillary architecture with abundant eosinophilic cytoplasm and empty or ground glass nuclei with occasional nuclear grooves and inconspicuous nucleoli, whereas the stroma was abundant in mucinous material exhibiting a positive reaction for PAS staining. One case (case 21, a molecularly confirmed ASPL-TFE3 RCC) had a tubular, tubulopapillary and solid growth patterns and was associated with a desmoplastic stroma. Small papillary infoldings, microcystic change and occasional psammoma bodies were observed. The cells of tumor displayed high-grade (Fuhrman 3 and 4) nuclear features and had a hobnail pattern of growth with eosinophilic cytoplasm, reminiscent of collecting duct carcinoma. Case 22 consisted of solid sheets and nests of epithelioid cells with clear to finely granular cytoplasm, distinct cell borders, and distinct nucleoli separated by delicate fibrovascular septa. Scattered dark brown pigment, which seemed to be melanin, were evident in the cytoplasm of the tumor cells. The morphology of present case is identical to recently recognized pediatric aggressive epithelioid neoplasm, which was regarded as melanotic Xp11 translocation renal carcinoma. Case 23 which was a ASPL-TFE3 RCC confirmed by RT-PCR, contained rounded epithelioid and plump spindle cells arranged in solid sheets, often with perivascular cuffing of epithelioid cells, mimicking epithelioid angiomyolipoma. Nuclei were generally round, with distinct nucleoli. No psammoma bodies were detected. Finally, the remaining one case demonstrated cell with abundant eosinophilic cytoplasm, indistinct cell borders and conspicuous nucleoli, which were arranged in cords, nests, trabecula, and organoid pattern and separated by several fibrovascular, edematous and hyalinized stroma, similar to those that have been observed in neuroendocrine tumor or oncocytoma.VHL gene analysis revealed deletions at 3p25-26 in one clear cell RCC and one papillary type 2 RCC. The papillary type 2 RCC was also presented with a family history of VHL disease and found a germline mutation Gâ†'C on a splicing site at position 553+5. The present case widens the spectrum of microscopic features to be found in VHL-associated RCC. There were no VHL mutations in the remaining 50 RCCs. RT-PCR performed on RNA extracted from frozen and non-neoplastic tissue (the distance from tumor tissue>10cm) identified a reciprocal ASPL-TFE3 fusion transcripts in 3 cases, consistent with the translocation of t(X;17)(p11.2;q25). To confirm the presence of a TFE3 gene rearrangement, TFE3 FISH analysis was performed.24 tumors showed evidence of a TFE3 gene rearrangement. Statistical analysis of stage and outcome revealed that TFE+juvenile RCCs were significantly more frequently associated with a higher pTNM pT3/pT4 stage and a poorer outcome than TFE-RCCs (P<0.05). A total of 4 studies were included for meta-analysis and pooled odds ratios (ORs) with 95% confidence interval (CI) were calculated. Our meta-analysis outcomes showed that TFE3+juvenile RCCs were significantly associated with a poorer outcomes (OS and DFS) and a higher stage (â…¢/â…£) than TFE3-RCCs (pooled ORs for each group:4.59 (95% CI 1.46-14.42) for OS; 5.79 (95% CI 1.85-18.16) for DFS and 5.89 (95% CI 2.23-15.52) for stage).CONCLUSION:(1) Juvenile RCCs are rare. The majority of RCCs in this age group were Xp11.2 translocation RCCs and papillary RCCs. (2) The majority of RCC in children and adolescents should be independent of VHL defects. (3) The present case of papillary type 2 RCC widens the spectrum of microscopic features to be found in VHL-associated RCC. (4) Xp11.2 translocation RCCs with different genetic variants may have different morphologic features, and different morphologic features may be present in tumors with the same genetic variant. (5) Identification of overexpression of TFE3 protein is still useful method for the diagnosis of Xp11 translocation RCC. (6) TFE3-associated dual-color, break-apart FISH assay can be used as a sensitive, specific and quick method for the diagnosis of Xp11 RCC. It should be applied for the pathological diagnosis. (7) TFE3+juvenile RCCs were significantly associated with a poorer outcomes (OS and DFS) and a higher stage (â…¢/â…£) than TFE3- RCCs. Owing to the already known aggressive behavior of these Xp11.2 translocation RCCs, patients with TFE+ juvenile RCCs should benefit from a more strict follow-up.