Non-coding RNA and gene expression analyses of papillary renal neoplasm with reverse polarity (PRNRP) reveal distinct pathological mechanisms from other renal neoplasms

Papillary renal neoplasm with reversed polarity (PRNRP) is a recently described rare renal neoplasm. Traditionally, it was considered a variant of papillary renal cell carcinoma (PRCC). However, several studies reported significant differences between PRNRP and PRCC in terms of clinical, morphological, immunohistochemical and molecular features. Nonetheless, PRNRP remains a poorly understood entity. We used microarray analysis to elucidate the non-coding RNA (ncRNA) and gene expression profiles of 10 PRNRP cases and compared them with other renal neoplasms. Unsupervised cluster analysis showed that PRNRP had distinct expression profiles from either clear cell renal cell carcinoma (ccRCC) or PRCC cases at the level of ncRNA but were less distinct at the level of gene expression. An integrated omic approach determined miRNA:gene interactions that distinguished PRNRP from PRCC and we validated 10 differentially expressed miRNAs and six genes by quantitative RT-PCR. We found that levels of the miRNAs, miR-148a, miR-375 and miR-429, were up-regulated in PRNRP cases compared to ccRCC and PRCC. miRNA target genes, including KRAS and VEGFA oncogenes, and CXCL8, which regulates VEGFA, were also differentially expressed between renal neoplasms. Gene set enrichment analysis (GSEA) determined different activation of metabolic pathways between PRNRP and PRCC cases. Overall, this study is by far the largest molecular study of PRNRP cases and the first to investigate either ncRNA expression or their gene expression by microarray assays.

Vascular, adipose tissue, and/or calyceal invasion in clear cell tubulopapillary renal cell tumour: potentially problematic diagnostic scenarios

AIMS

The 2022 WHO classification for kidney tumours recently downgraded clear cell tubulopapillary (also known as clear cell papillary) renal cell carcinoma (RCC) to a benign neoplasm (i.e. clear cell tubulopapillary renal cell tumour) based on the overwhelmingly banal nature of this neoplasm. However, it has been recognized that some clear cell tubulopapillary renal cell tumours demonstrate vascular, adipose or pelvicalyceal invasion, raising the possibility of more aggressive behaviour. The goal of this study was to determine if these 'high stage' features have an effect on tumour prognosis, warranting a carcinoma designation.

METHODS AND RESULTS

After excluding cases with tissue artefact (i.e. prior core biopsy track changes) and other RCC subtypes with next-generation sequencing, nine clear cell tubulopapillary renal cell tumours with these so-called 'high stage' features, and otherwise classic morphologic and immunophenotypic findings, including low-grade cytology and 'cup-like' CA9 expression, were evaluated. Median tumour size was 2.2 cm with a range of 0.8 to 6.7 cm. Eight cases (89%) demonstrated perinephric or hilar adipose tissue invasion, although most of these cases showed a bulging (in contrast to an infiltrative) growth pattern. One case demonstrated renal vascular invasion in addition to hilar adipose tissue invasion, and one case demonstrated extension into the pelvicalyceal system. There were no recurrences or evidence of metastatic disease.

CONCLUSION

These overall findings continue to support the benign designation for clear cell tubulopapillary renal cell tumours, despite morphologic features that might raise the possibility of a 'higher stage' neoplasm.

Clear-cell papillary renal cell tumour: New insights into clinicopathological features and molecular landscape after renaming by 5th WHO classification

OBJECTIVE

Clear cell papillary renal cell tumour (CCPRCT) is a kind of renal epithelial cell tumor, and was renamed by the 5th WHO due to its specific epidemiology and clinicopathological characteristics. However, the biological mechanism and molecular basis of CCPRCT still need to be further clarified. This study aims to comprehensively evaluate clinicopathologic and molecular characteristics of CCPRCC, and particularly compare it with other more prevalent subtypes of renal cell carcinoma.

METHODS

12 cases of CCPRCT were collected for analyzing the clinicopathological characteristics. Then, whole-exome sequencing (WES) was employed to reveal the genetic profiles, followed by comparison with the molecular genetic alterations identified in ccRCC (341) and pRCC (200) datasets obtained from the TCGA database.

RESULTS

Of the 12 CCPRCT cases, the male-to-female ratio was 4:1 with a mean age of 49.5 years (48.5 ± 10.5) at diagnosis. All patients were diagnosed accidentally during routine physical examinations. All tumors (12/12, 100%）had a solid-cystic appearance with a well-defined fibrous capsule. The median size of the tumors was 3 cm (2.98 ± 1.2). Histologically, the cystic papillary structures were considered to be prominent, lined with cuboidal tumor cells away from basement membrane. The tumor cells were moderately atypia equivalent to grade 1 or grade 2 according to the ISUP nuclear grading system. Typically, the tumor cell diffusely positive for CK7 and CAIX in a "cup-like" pattern. The results of WES revealed recurrent gene alterations (mainly missense mutation) of TTN and FLT in 4 cases (4/12, 33.3%), respectively, of which, the alteration of FLT was not observed in ccRCC and pRCC of the TCGA database. Other gene alterations including POTEC (1 cases), PRADC1 (1 cases), ZZZ3 (1 case) and PTPRZ1 (1 case), etc. Moreover, all of the CCPRCT cases displayed a lower tumor mutation burden (TMB) compared to ccRCC and pRCC with median TMB of 1.04 (range: 1.94 ± 2.74). None of the patients experienced tumor metastasis, recurrence, or tumor-related deaths.

CONCLUSION

CCPRCT is a renal epithelial cell tumor characterized by specific clinical and pathological features. Our study provides additional evidence supporting the favorable prognosis of CCPRCT. Furthermore, the potential molecular alterations were uncovered by this study in CCPRCT such as the FLT family and TTN. However, due to the limited sample size, larger studies are required to validate these findings.

Midsize noncoding RNAs in cancers: a new division that clarifies the world of noncoding RNA or an unnecessary chaos?

Most of the human genome is made out of noncoding RNAs (ncRNAs). These ncRNAs do not code for proteins but carry a vast number of important functions in human cells such as: modification and processing other RNAs (tRNAs, rRNAs, snRNAs, snoRNAs, miRNAs), help in the synthesis of ribosome proteins, initiation of DNA replication, regulation of transcription, processing of pre-messenger mRNA during its maturation and much more. The ncRNAs also have a significant impact on many events that occur during carcinogenesis in cancer cells, such as: regulation of cell survival, cellular signaling, apoptosis, proliferation or even influencing the metastasis process. The ncRNAs may be divided based on their length, into short and long, where 200 nucleotides is the "magic" border. However, a new division was proposed, suggesting the creation of the additional group called midsize noncoding RNAs, with the length ranging from 50-400 nucleotides. This new group may include: transfer RNA (tRNA), small nuclear RNAs (snRNAs) with 7SK and 7SL, small nucleolar RNAs (snoRNAs), small Cajal body-specific RNAs (scaRNAs) and YRNAs. In this review their structure, biogenesis, function and influence on carcinogenesis process will be evaluated. What is more, a question will be answered of whether this new division is a necessity that clears current knowledge or just creates an additional misunderstanding in the ncRNA world?

How New Developments Impact Diagnosis in Existing Renal Neoplasms

In recent years, several emerging diagnostic entities have been described in renal cell carcinoma (RCC). However, our understanding of well-known and established entities has also grown. Clear cell papillary RCC is now relabeled as a tumor rather than carcinoma in view of its nonaggressive behavior. Renal tumors with a predominantly infiltrative pattern are very important for recognition, as most of these have aggressive behavior, including fumarate hydratase-deficient RCC, SMARCB1-deficient medullary carcinoma, collecting duct carcinoma, urothelial carcinoma, and metastases from other cancers.

Renal Cell Carcinoma in End-Stage Renal Disease: A Review and Update

Renal cell carcinoma (RCC) occurring in the setting of end-stage renal disease (ESRD) shows unique clinicopathological characteristics. The two most frequent types of ESRD-associated RCC are acquired cystic kidney disease-associated renal cell carcinoma (ACKD-RCC) and clear-cell papillary renal cell carcinoma (ccpRCC). Other types of RCC also occur in ESRD, albeit with different frequencies from the non-ESRD general population. The histological features of RCC do not vary in the setting of ESRD vs. non-ESRD, yet other findings, such as multifocality and multiple tumor types, are more frequent in ESRD. Studies have generated novel and important knowledge of the etiology, epidemiology, diagnosis, treatment, immunophenotype, and molecular characteristics of ESRD-associated RCC. Knowledge of these data is important for both pathologists and other physicians who may encounter ESRD patients with RCC. This review presents a comprehensive summary and update of the literature on RCC in ESRD, with a focus on the two most frequent types, ACKD-RCC and ccpRCC.

Characteristics of Clear Cell Papillary Renal Cell Carcinoma (ccpRCC)

Renal cell carcinomas (RCCs) is a group of various malignant tumours of the renal cortex displaying distinct clinical, morphologic, and genetic features. Clear cell papillary renal cell carcinoma (ccpRCC), belonging to this group, shares morphologic features with both clear cell renal cell carcinoma (ccRCC) and papillary renal cell carcinoma (pRCC) and therefore, more strict diagnostic criteria should be developed to avoid misdiagnosis. Despite overlapping features, ccpRCC has also distinct clinical behaviour, histologic characteristics (morphologic and immunohistochemical), and genomic features. The concepts concerning this tumour are constantly developing since its biological potential and molecular basis remains to be fully unravelled. First reports indicated the presence of ccpRCC in end-stage renal disease, and they underlined the enriched development in this group of patients; however, currently, it is known that such tumours can also occur spontaneously in the normal kidney. Numerous studies have demonstrated that clinical outcomes and prognosis of ccpRCC patients is highly favourable. Till now, no convincing evidence of metastatic ccpRCC or death caused by the disease has been found. Therefore, it is of high importance to correctly differentiate ccpRCC from other subtypes of RCC with a much worse prognosis and to introduce appropriate management.

Nucleolar Proteins and Non-Coding RNAs: Roles in Renal Cancer

Renal cell cancer is the most frequent kidney malignancy. Most RCC cases are classified as clear cell renal cell carcinoma (ccRCC), characterized by high aggressiveness and poor prognosis for patients. ccRCC aggressiveness is defined by classification systems based on changes in morphology of nucleoli, the membraneless substructures of nuclei. The latter act as the sites of ribosome biogenesis as well as the hubs that trap and immobilize proteins, preventing their action in other cellular compartments. Thereby, nucleoli control cellular functioning and homeostasis. Nucleoli are also the sites of activity of multiple noncoding RNAs, including snoRNAs, IGS RNA, and miRNAs. Recent years have brought several remarkable discoveries regarding the role of nucleolar non-coding RNAs, in particular snoRNAs, in ccRCC. The expression of snoRNAs is largely dysregulated in ccRCC tumors. snoRNAs, such as SNHG1, SNHG4 and SNHG12, act as miRNA sponges, leading to aberrant expression of oncogenes and tumor suppressors, and directly contributing to ccRCC development and progression. snoRNAs can also act without affecting miRNA functioning, by altering the expression of key oncogenic proteins such as HIF1A. snoRNAs are also potentially useful biomarkers of ccRCC progression. Here, we comprehensively discuss the role of nucleolar proteins and non-coding RNAs in ccRCC.

Clear Cell Papillary Renal Cell Carcinoma Shares Distinct Molecular Characteristics and may be Significantly Associated With Higher Risk of Developing Second Primary Malignancy

Traditionally, clear cell papillary renal cell carcinoma (ccpRCC) was considered to share similar molecular and histological characteristics with clear cell renal cell carcinoma (ccRCC) and papillary renal cell carcinoma (pRCC). Here we aimed to identify somatic and germline variants of ccpRCC. For this purpose, we conducted whole-exome sequencing to detect somatic variants in the tissues of 18 patients with pathologically confirmed ccpRCC, who underwent surgical treatment at Fudan University Shanghai Cancer Center. Targeted sequencing was conducted to detect germline variants in paired tumor or normal tissues or blood. Somatic and germline variants of ccRCC and Renal cell carcinoma included in The Cancer Genome Atlas data and other published data were analyzed as well. The molecular profiles of ccpRCC, ccRCC and pRCC were compared. Among the 387 somatic variants identified, TCEB1 (3/18) and VHL (3/18) variants occurred at the highest frequencies. Germline mutation detection showed that nine variants associated with Fanconi anemia (VAFAs) pathway (FANCA, 6/18; FANCI, 3/18) were identified in 18 ccpRCC patients. Among ccpRCC patients with VAFAs, five out of eight patients had second primary malignancy or family history of cancer. Somatic variants characteristics may distinguish ccpRCC from ccRCC or pRCC and germline VAFAs may be a molecular characterization of ccpRCC. Compared with ccRCC or pRCC, ccpRCC patients may be significantly correlated with higher risk of developing second primary malignancy.

Integrated mRNA and miRNA Transcriptomic Analyses Reveals Divergent Mechanisms of Sunitinib Resistance in Clear Cell Renal Cell Carcinoma (ccRCC)

Simple Summary

Clear cell renal cell carcinoma (ccRCC) is a frequent cancer that causes more than 100,000 deaths every year. Treatment with drugs that target enzymes that help tumours grow such as sunitinib have greatly improved the prospects for ccRCC patients, however a large proportion of patients become resistant. We created sunitinib resistant cell lines and identified consequent changes in gene (and miRNA) expression by microarray analyses. Using this approach, we identified different pathways of resistance suggesting that tumour cells have many ways to overcome sunitinib treatment. We were able to overcome resistance in cells by inhibiting a protein, PD-L1, that is targeted by many immunotherapeutics currently in use for ccRCC patients suggesting a combination of immunotherapy and sunitinib may benefit patients. In addition, we identified miRNAs that are common to multiple resistance mechanisms suggesting they may be useful targets for future studies.

Abstract

The anti-angiogenic therapy sunitinib remains the standard first-line treatment for meta static clear cell renal cell carcinoma (ccRCC). However, acquired resistance develops in nearly all responsive patients and represents a major source of treatment failure. We used an integrated miRNA and mRNA transcriptomic approach to identify miRNA:target gene interactions involved in sunitinib resistance. Through the generation of stably resistant clones in three ccRCC cell lines (786-O, A498 and Caki-1), we identified non-overlapping miRNA:target gene networks, suggesting divergent mechanisms of sunitinib resistance. Surprisingly, even though the genes involved in these networks were different, they shared targeting by multiple members of the miR-17~92 cluster. In 786-O cells, targeted genes were related to hypoxia/angiogenic pathways, whereas, in Caki-1 cells, they were related to inflammatory/proliferation pathways. The immunotherapy target PD-L1 was consistently up-regulated in resistant cells, and we demonstrated that the silencing of this gene resulted in an increase in sensitivity to sunitinib treatment only in 786-O-resistant cells, suggesting that some ccRCC patients might benefit from combination therapy with PD-L1 checkpoint inhibitors. In summary, we demonstrate that, although there are clearly divergent mechanisms of sunitinib resistance in ccRCC subtypes, the commonality of miRNAs in multiple pathways could be targeted to overcome sunitinib resistance.

Relationship between miR-155 expression and clear cell papillary renal cell carcinoma in the dialyzed kidney

INTRODUCTION

Clear cell papillary renal cell carcinoma often develops in the context of the dialyzed kidney (end-stage renal disease). However, the relationship between clear cell papillary renal cell carcinoma and microRNA expression in patients with end-stage renal disease remains unclear.

CASE PRESENTATION

A left renal tumor measuring 22 mm was detected and a radical nephrectomy was performed on a 50-year-old man who had received hemodialysis for the past 6 years. A pathological diagnosis of pT1aNxMx, clear cell papillary renal cell carcinoma was made. We studied the expression of miR-155 in this case and compared it to the expression in nondialysis kidney tissue. The expression level of miR-155 was upregulated in tumor tissue compared with expression levels in the renal cortex for the present case. The expression level of miR-155 in the renal cortex was lower in the present case than in nondialysis kidney tissues.

CONCLUSION

We demonstrated upregulation of miR-155 in a case of clear cell papillary renal cell carcinoma arising from end-stage renal disease.

The Role of Epigenetics in the Progression of Clear Cell Renal Cell Carcinoma and the Basis for Future Epigenetic Treatments

Simple Summary

The accumulated evidence on the role of epigenetic markers of prognosis in clear cell renal cell carcinoma (ccRCC) is reviewed, as well as state of the art on epigenetic treatments for this malignancy. Several epigenetic markers are likely candidates for clinical use, but still have not passed the test of prospective validation. Development of epigenetic therapies, either alone or in combination with tyrosine-kinase inhibitors of immune-checkpoint inhibitors, are still in their infancy.

Abstract

Clear cell renal cell carcinoma (ccRCC) is curable when diagnosed at an early stage, but when disease is non-confined it is the urologic cancer with worst prognosis. Antiangiogenic treatment and immune checkpoint inhibition therapy constitute a very promising combined therapy for advanced and metastatic disease. Many exploratory studies have identified epigenetic markers based on DNA methylation, histone modification, and ncRNA expression that epigenetically regulate gene expression in ccRCC. Additionally, epigenetic modifiers genes have been proposed as promising biomarkers for ccRCC. We review and discuss the current understanding of how epigenetic changes determine the main molecular pathways of ccRCC initiation and progression, and also its clinical implications. Despite the extensive research performed, candidate epigenetic biomarkers are not used in clinical practice for several reasons. However, the accumulated body of evidence of developing epigenetically-based biomarkers will likely allow the identification of ccRCC at a higher risk of progression. That will facilitate the establishment of firmer therapeutic decisions in a changing landscape and also monitor active surveillance in the aging population. What is more, a better knowledge of the activities of chromatin modifiers may serve to develop new therapeutic opportunities. Interesting clinical trials on epigenetic treatments for ccRCC associated with well established antiangiogenic treatments and immune checkpoint inhibitors are revisited.

The Clinicopathologic and Molecular Landscape of Clear Cell Papillary Renal Cell Carcinoma: Implications in Diagnosis and Management

BACKGROUND

Clear cell papillary renal cell carcinoma (CCPRCC) is a recently described tumor entity. Several questions remain about its epidemiology, molecular features, and clinical behavior.

OBJECTIVE

To comprehensively evaluate clinicopathologic and molecular features of CCPRCC, and compare it with more common kidney cancer subtypes.

DESIGN, SETTING, AND PARTICIPANTS

We identified 89 CCPRCC patients and compared their clinicopathologic features with 1120 localized clear cell renal cell carcinoma (ccRCC) and 129 type 1 papillary renal cell carcinoma (pRCC) patients.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Nonparametric statistical testing was used to compare relevant features between tumor types. Overall, cancer-specific survival (CSS) and metastasis-free survival estimates were calculated from initial diagnosis using the Kaplan-Meier method. Patients with ipsilateral multifocal disease were explored further. A subset of CCPRCC tumors underwent genomic analysis and were compared with other RCC subtypes.

RESULTS AND LIMITATIONS

A higher proportion of female (45% vs 32%) and African-American (19% vs 3%) patients were observed in the CCPRCC cohort than in the ccRCC and pRCC cohorts. CCPRCC tumors also had increased odds of presenting with additional ipsilateral masses (odds ratio [OR]: 4.41 [confidence interval {CI}: 2.34, 8.15], p < 0.001) and bilateral disease (OR: 4.80 [CI: 2.40, 9.59], p < 0.001) compared with ccRCC tumors. On molecular analysis, CCPRCC tumors showed fewer somatic aberrations and a greater degree of mitochondrial DNA depletion. In multifocal CCPRCC tumors, histologic concordance among the different renal cell carcinoma masses was estimated at 44% (7/16), and none of the individuals presenting exclusively with CCPRCC tumors developed metastatic disease after 5 yr. In contrast, multifocal tumors with CCPRCC and other nonconcordant histologies were more likely to experience adverse outcomes (CSS, log rank p = 0.034).

CONCLUSIONS

CCPRCC is characterized by distinct molecular and epidemiologic features that could be used to refine current diagnostic approaches. Although their clinical course is generally indolent, multifocal CCPRCC tumors represent a unique diagnostic challenge. In this context, single-mass biopsies could miss concomitant aggressive disease, with a potential negative impact on patient outcomes. Furthermore, high discordance rates in multifocal CCPRCC tumors have important clinical implications in management.

PATIENT SUMMARY

We explored the molecular and clinical features of clear cell papillary renal cell carcinoma (CCPRCC) relative to other kidney cancer subtypes. While CCPRCC generally conveys a good prognosis, additional caution should be taken when it is diagnosed using biopsy if multiple kidney masses are present.

Identification of RCC Subtype-Specific microRNAs-Meta-Analysis of High-Throughput RCC Tumor microRNA Expression Data

Renal cell carcinoma (RCC) is one of the most common cancers worldwide with a nearly non-symptomatic course until the advanced stages of the disease. RCC can be distinguished into three subtypes: papillary (pRCC), chromophobe (chRCC) and clear cell renal cell carcinoma (ccRCC) representing up to 75% of all RCC cases. Detection and RCC monitoring tools are limited to standard imaging techniques, in combination with non-RCC specific morphological and biochemical read-outs. RCC subtype identification relays mainly on results of pathological examination of tumor slides. Molecular, clinically applicable and ideally non-invasive tools aiding RCC management are still non-existent, although molecular characterization of RCC is relatively advanced. Hence, many research efforts concentrate on the identification of molecular markers that will assist with RCC sub-classification and monitoring. Due to stability and tissue-specificity miRNAs are promising candidates for such biomarkers. Here, we performed a meta-analysis study, utilized seven NGS and seven microarray RCC studies in order to identify subtype-specific expression of miRNAs. We concentrated on potentially oncocytoma-specific miRNAs (miRNA-424-5p, miRNA-146b-5p, miRNA-183-5p, miRNA-218-5p), pRCC-specific (miRNA-127-3p, miRNA-139-5p) and ccRCC-specific miRNAs (miRNA-200c-3p, miRNA-362-5p, miRNA-363-3p and miRNA-204-5p, 21-5p, miRNA-224-5p, miRNA-155-5p, miRNA-210-3p) and validated their expression in an independent sample set. Additionally, we found ccRCC-specific miRNAs to be differentially expressed in ccRCC tumor according to Fuhrman grades and identified alterations in their isoform composition in tumor tissue. Our results revealed that changes in the expression of selected miRNA might be potentially utilized as a tool aiding ccRCC subclass discrimination and we propose a miRNA panel aiding RCC subtype distinction.

Clear cell papillary renal cell carcinoma: an update after 15 years

Fifteen years since the first recognition of clear cell papillary renal cell carcinoma, this distinct renal tumour type is now well accepted as a distinct entity in major classification schemes. It occurs both with and without end-stage renal disease and may be multifocal or bilateral in both scenarios. Recognisable morphological features include clear cells lining branching glands and variable papillary formations with nuclear alignment. Most tumours are small (pT1a) and nucleolar grade 1-2. Immunohistochemistry consistently shows positivity for carbonic anhydrase IX and cytokeratin 7, and often high molecular weight cytokeratin or GATA3, the latter suggesting distal nephron phenotype. Labeling for AMACR and CD10 is consistently negative or minimal. Despite a resemblance to clear cell renal cell carcinoma, molecular alterations of VHL and chromosome 3p are typically lacking, with debatable rare exceptions. Potential mimics include clear cell renal cell carcinoma (with branching architecture or nuclear alignment), papillary renal cell carcinoma with clear cytoplasm, or rarely MITF family translocation renal cell carcinoma. Clinical behaviour is highly favourable with rare, debatable reports of aggressive behaviour. Combined with striking similarity to several extrarenal benign neoplasms, it would be reasonable to reclassify this entity as a benign or low malignant potential neoplasm. Using the nomenclature of the extrarenal counterparts, clear cell papillary (cyst)adenoma is proposed.

Similarities and Differences between Clear Cell Tubulo-Papillary and Conventional Clear Cell Renal Cell Carcinoma: A Comparative Phenotypical and Mutational Analysis

Background: Clear cell tubulo-papillary renal cell carcinoma (cctpRCC) is characterized by clear cell morphology, but differs from conventional clear cell carcinoma (ccRCC) for its indolent clinical behavior and genetic background. The differential diagnosis between the two is based on histology and immunohistochemistry (IHC). Methods: We performed a comparative case-control histological, IHC, and genetic analysis by next generation sequencing (NGS), to point out the differences in 10 cases of cctpRCC, and six controls of ccRCC with low stage and grade. Results: All 16 cases showed the IHC profile with cytokeratin 7, racemase, and carbonic anhydrase IX expected for the histological features of each tumor type. By contrast, the NGS mutation analysis that covered 207 amplicons of 50 oncogenes or tumor suppressor genes provided conflicting results. Among the 10 cctpRCC cases, eight (80%) were wild type for all of the genes in the panel, while two (20%) harbored VHL mutations typical of ccRCC. Three of the six (50%) ccRCC control cases showed expected VHL mutations; two (33%) harbored pathogenic mutations in the p53 or the CKIT genes; and one (16%) was wild type. Conclusion: We can assume that histology and ICH are not sufficient for a definitive diagnosis of cctpRCC or ccRCC. Although with a panel covering 50 genes, we found that 80% of cctpRCC were genetically silent; thus, suggesting an indolent biology of these tumors. The differential diagnosis between ccptRCC and ccRCC for the choice of the best therapeutic strategy likely requires the comprehensive evaluation of histology, IHC, and at least VHL mutations.

Current Concepts of Non-Coding RNAs in the Pathogenesis of Non-Clear Cell Renal Cell Carcinoma

Renal cell carcinoma (RCC) is a relatively rare malignancy of the urinary tract system. RCC is a heterogenous disease in terms of underlying histology and its associated underlying pathobiology, prognosis and treatment schedule. The most prevalent histological RCC subtype is clear-cell renal cell carcinoma (ccRCC), accounting for about 70-80% of all RCCs. Though the pathobiology and treatment schedule for ccRCC are well-established, non-ccRCC subtypes account for 20%-30% of RCC altogether, and their underlying molecular biology and treatment options are poorly defined. The class of non-coding RNAs-molecules that are generally not translated into proteins-are new cancer drivers and suppressors in all types of cancer. Of these, small non-coding microRNAs (miRNAs) contribute to carcinogenesis by regulating posttranscriptional gene silencing. Additionally, a growing body of evidence supports the role of long non-coding RNAs (lncRNAs) in cancer development and progression. Most studies on non-coding RNAs in RCC focus on clear-cell histology, and there is a relatively limited number of studies on non-ccRCC subtypes. The aim of this review is to give an overview of the current knowledge regarding the role of non-coding RNAs (including short and long non-coding RNAs) in non-ccRCC and to highlight possible implications as diagnostic, prognostic and predictive biomarkers.

Analysis of Expression Pattern of snoRNAs in Different Cancer Types with Machine Learning Algorithms

Small nucleolar RNAs (snoRNAs) are a new type of functional small RNAs involved in the chemical modifications of rRNAs, tRNAs, and small nuclear RNAs. It is reported that they play important roles in tumorigenesis via various regulatory modes. snoRNAs can both participate in the regulation of methylation and pseudouridylation and regulate the expression pattern of their host genes. This research investigated the expression pattern of snoRNAs in eight major cancer types in TCGA via several machine learning algorithms. The expression levels of snoRNAs were first analyzed by a powerful feature selection method, Monte Carlo feature selection (MCFS). A feature list and some informative features were accessed. Then, the incremental feature selection (IFS) was applied to the feature list to extract optimal features/snoRNAs, which can make the support vector machine (SVM) yield best performance. The discriminative snoRNAs included HBII-52-14, HBII-336, SNORD123, HBII-85-29, HBII-420, U3, HBI-43, SNORD116, SNORA73B, SCARNA4, HBII-85-20, etc., on which the SVM can provide a Matthew’s correlation coefficient (MCC) of 0.881 for predicting these eight cancer types. On the other hand, the informative features were fed into the Johnson reducer and repeated incremental pruning to produce error reduction (RIPPER) algorithms to generate classification rules, which can clearly show different snoRNAs expression patterns in different cancer types. The analysis results indicated that extracted discriminative snoRNAs can be important for identifying cancer samples in different types and the expression pattern of snoRNAs in different cancer types can be partly uncovered by quantitative recognition rules.

Abnormal oxidative metabolism in a quiet genomic background underlies clear cell papillary renal cell carcinoma

While genomic sequencing routinely identifies oncogenic alterations for the majority of cancers, many tumors harbor no discernable driver lesion. Here, we describe the exceptional molecular phenotype of a genomically quiet kidney tumor, clear cell papillary renal cell carcinoma (CCPAP). In spite of a largely wild-type nuclear genome, CCPAP tumors exhibit severe depletion of mitochondrial DNA (mtDNA) and RNA and high levels of oxidative stress, reflecting a shift away from respiratory metabolism. Moreover, CCPAP tumors exhibit a distinct metabolic phenotype uniquely characterized by accumulation of the sugar alcohol sorbitol. Immunohistochemical staining of primary CCPAP tumor specimens recapitulates both the depletion of mtDNA-encoded proteins and a lipid-depleted metabolic phenotype, suggesting that the cytoplasmic clarity in CCPAP is primarily related to the presence of glycogen. These results argue for non-genetic profiling as a tool for the study of cancers of unknown driver.

Clear Cell Papillary Renal Cell Carcinoma

Clear cell papillary renal cell carcinoma (ccpRCC) is a recently recognized entity and represents the fourth most common variant of renal cell carcinoma (RCC). It has unique morphologic and immunohistochemical features and demonstrates an indolent clinical behavior. Microscopically, it may mimic other RCCs with clear cell features, such as clear cell RCC, translocation RCC, and papillary RCC with clear cell changes. A high index of suspicion is required to keep ccpRCC in the differential diagnosis of RCCs with features of clear cell and/or papillary architecture. In equivocal cases, immunohistochemistry is generally sufficient to substantiate the diagnosis of ccpRCC. In this review, we discuss the clinical, gross, and histopathologic features, immunohistochemical and genetic profiling, and prognosis of ccpRCC.

miR‑122 promotes proliferation and invasion of clear cell renal cell carcinoma by suppressing Forkhead box O3

MicroRNAs (miRNAs) serve an important role in renal cancer, but renal cancer miRNA expression data remains inconsistent. Therefore, there is a requirement for integrated analysis of these data. An increasing number of studies demonstrate that miR‑122 is dysregulated in numerous cancer types, including liver, lung and breast cancer, yet its role in clear cell renal cell carcinoma (ccRCC) remains unclear. In the present study, an integrated analysis of four ccRCC miRNAs expression datasets was performed and the expression of miR‑122 in the present cohort was validated. The effects of cell proliferation, colony formation, migration and invasion of ccRCC cells in vitro were assayed following transfection with miR‑122 mimics and inhibitor. The target gene of miR‑122 was confirmed using a luciferase reporter assay, and a xenograft mouse model was used to determine the effect of miR‑122 in ccRCC tumorigenicity in vivo. The present results demonstrated that patients with ccRCC with an increased miR‑122 level in tumor tissues had a shortened metastasis‑free survival time as indicated by The Cancer Genome Atlas‑Kidney Renal Clear Cell Carcinoma dataset and the present ccRCC cohort. Overexpression of miR‑122 in 786‑O cells improved cell proliferation, colony formation, migration and invasion, while knockdown of miR‑122 in SN12‑PM6 cells inhibited cell growth, colony formation, migration and invasion. Western blot analysis and luciferase reporter assays were used to identify FOXO3 as a direct target of miR‑122. The present results indicate that miR‑122 serves a tumor‑promoting role by direct targeting FOXO3 in ccRCC.

Clinical features and survival analysis of clear cell papillary renal cell carcinoma: A 10-year retrospective study from two institutions

Clear cell papillary renal cell carcinoma (CCPRCC) is a recently recognized subtype of renal cell carcinoma entity, however, little is known about its clinical features. In the present study, 26 cases of CCPRCC were screened out from two institutions. The patient data, tissue pathology, immunohistochemical phenotype, computed tomographic images and survival analysis were studied. The mean age was 53.3 years and the average tumor size was 2.5 cm. A total of 17 patients' body mass indexes were higher than the normal level. A total of 11 patients had hypertension and 6 patients had a smoking history. Histopathologically, all cases of CCPRCC exhibited a tubular and papillary architecture, small to medium-sized cuboidal tumor cells with clear cytoplasms, and a low Fuhrman nuclear grade. All tumors were encapsulated by variably thick fibrous capsules. Immunohistochemistry showed diffuse and moderate to strong cytoplasmic staining for CK7, CA IX and vimentin, but negative for AMACR and CD10 (sometimes focally positive) in all cases. According to the results of Ki67 labeling index, the expression of Ki67 in CCPRCC was much lower than that in clear cell renal cell carcinoma (CCRCC) (2.19 vs. 7.07%, P<0.001) and that in papillary renal cell carcinoma (PRCC) (2.19 vs. 6.65%, P<0.001). Radiographically, the tumors were shown as small masses with smooth contour and mixed enhancement pattern. The multiphasic attenuation curve for CCPRCC, like that for CCRCC, increased in the corticomedullary phase markedly and decreased in the nephrographic phase and excretory phase gradually. At a median follow-up period of 50 months, no cancer-specific death or tumor recurrence was observed. Considering the favorable prognosis of CCPRCC, preoperative biopsy in order to make clear the diagnosis is particularly important. In light of the present findings, partial nephrectomy for patients with CCPRCC is recommended. If the patients cannot tolerate surgery, closed monitoring or radiofrequency ablation may be considered.

Noncoding RNA Expression and Targeted Next-Generation Sequencing Distinguish Tubulocystic Renal Cell Carcinoma (TC-RCC) from Other Renal Neoplasms

Tubulocystic renal cell carcinoma (TC-RCC) is a rare recently described renal neoplasm characterized by gross, microscopic, and immunohistochemical differences from other renal tumor types and was recently classified as a distinct entity. However, this distinction remains controversial particularly because some genetic studies suggest a close relationship with papillary RCC (PRCC). The molecular basis of this disease remains largely unexplored. We therefore performed noncoding (nc) RNA/miRNA expression analysis and targeted next-generation sequencing mutational profiling on 13 TC-RCC cases (11 pure, two mixed TC-RCC/PRCC) and compared with other renal neoplasms. The expression profile of miRNAs and other ncRNAs in TC-RCC was distinct and validated 10 differentially expressed miRNAs by quantitative RT-PCR, including miR-155 and miR-34a, that were significantly down-regulated compared with PRCC cases (n = 22). With the use of targeted next-generation sequencing we identified mutations in 14 different genes, most frequently (>60% of TC-RCC cases) in ABL1 and PDFGRA genes. These mutations were present in <5% of clear cell RCC, PRCC, or chromophobe RCC cases (n > 600) of The Cancer Genome Atlas database. In summary, this study is by far the largest molecular study of TC-RCC cases and the first to investigate either ncRNA expression or their genomic profile. These results add molecular evidence that TC-RCC is indeed a distinct entity from PRCC and other renal neoplasms.

DNA Methylation and Urological Cancer, a Step Towards Personalized Medicine: Current and Future Prospects

Urologic malignancies are some of the commonest tumors often curable when diagnosed at early stage. However, accurate diagnostic markers and faithful predictors of prognosis are needed to avoid over-diagnosis leading to overtreatment. Many promising exploratory studies have identified epigenetic markers in urinary malignancies based on DNA methylation, histone modification and non-coding ribonucleic acid (ncRNA) expression that epigenetically regulate gene expression. We review and discuss the current state of development and the future potential of epigenetic biomarkers for more accurate and less invasive detection of urological cancer, tumor recurrence and progression of disease serving to establish diagnosis and monitor treatment efficacies. The specific clinical implications of such methylation tests on therapeutic decisions and patient outcome and current limitations are also discussed.

Primary Renal Carcinoid with Bilateral Multiple Clear Cell Papillary Renal Cell Carcinomas

Clear cell papillary renal cell carcinoma (CCPRCC) is a newly recognized entity in the 2016 WHO classification and usually presents as a small, circumscribed, solitary mass of indolent nature. CCPRCCs could seldom occur in conjunction with other synchronous or metachronous kidney tumors and even less frequently as bilateral masses. To our knowledge, multiple bilateral CCPRCCs have never been described with the existence of a synchronous well-differentiated neuroendocrine tumor of the kidney and hence reported here as a unique case. This case report highlights the importance in considering this entity and its unusual presentation in the differential diagnosis as a possible mimicker of Von Hippel-Lindau syndrome.

MiR-200 Regulates Epithelial-Mesenchymal Transition in Anaplastic Thyroid Cancer via EGF/EGFR Signaling

This study was set to study the molecular mechanism underlying how miR-200 regulates EGF/EGFR signaling to involve in epithelial-mesenchymal transition (EMT) in anaplastic thyroid cancer (ATC) cells. Loss-of-function experiments of EGFR silencing by siRNA transfection was performed. Transfection of pre-miR-200s or anti-miR-200s was used to increase or decrease miR-200 transcripts. Real-time PCR, Western blot, immunohistochemistry, and transwell experiments were performed to determine the role of miR-200s in EMT and its role in EGF/EGFR-mediated EMT in vitro and in vivo. EGF/EGFR signaling activation increased the expression of mesenchymal marker vimentin in Nthy-ori 3-1 cells and decreased the expression of endothelial maker E-cadherin. EGF stimulation led to increased RhoA expression in Nthy-ori 3-1 cells. EGFR silencing resulted in decreased RhoA expression in SW1736 and ARO cells. EGF stimulation led to down-regulation of miR-200s and EMT. Restoration of miR-200 expression by pre-miR-200a/c transfection reversed the process, including increased E-cadherin and decreased vimentin. Down-regulation of miR-200 by anti-miR-200 effectively reduced miR-200. Matrigel invasion assay proved that restoration of miR-200 expression counteracted invasiveness. EGFR silencing decreased invasiveness in SW1736 cells, while down-regulation of miR-200s restored invasiveness. Xenograft tumors of SW1736 cells with cotransfection of anti-miR-200s and EGFR siRNA which kept the similar E-cadherin and vimentin expression with the untransfected controls. In ATC cells, miR-200s play a central role in EGF/EGFR-mediated invasiveness in vitro and EMT in vivo.

Renal Neoplasms With Overlapping Features of Clear Cell Renal Cell Carcinoma and Clear Cell Papillary Renal Cell Carcinoma: A Clinicopathologic Study of 37 Cases From a Single Institution

Clear cell papillary renal cell carcinoma (CCPRCC) was recently included in the International Society of Urological Pathology Vancouver Classification of Renal Neoplasia as a subtype of RCC that is morphologically, immunohistochemically, and genetically distinct from both clear cell renal cell carcinoma (CCRCC) and papillary renal cell carcinoma. In our clinical practice we have observed tumors with overlapping histologic features of CCPRCC and CCRCC; therefore, our aim was to describe the morphologic, immunohistochemical, and clinical characteristics of these tumors. We examined a large series of consecutive nephrectomies diagnosed as CCRCC and found 37 tumors with morphologic overlap between CCRCC and CCPRCC, identifying 2 patterns. Pattern 1 tumors (N=19) had areas diagnosable as CCRCC admixed with foci having a prominent linear arrangement of nuclei away from the basement membrane imparting a resemblance to CCPRCC; however, other morphologic features commonly seen in CCPRCC (such as branching acini and cystic spaces with papillary tufts) were not typical and, when present, were focal or poorly developed. Pattern 2 (N=18) tumors had 2 discrete areas, one area with an appearance strongly resembling CCPRCC and the other with higher grade nuclei and features diagnosable as CCRCC, sometimes including rhabdoid differentiation, sarcomatoid differentiation, necrosis, and high-stage disease. Four (21%) of the pattern 1 tumors had grade 3 nuclei in the CCRCC-like areas, and 4 were high stage (pT3a). Of the 16 immunostained pattern 1 tumors, all expressed cytokeratin 7 (CK7) at least focally in the CCPRCC-like areas, strongly and diffusely in 9 (56%) cases; 12 (75%) showed negative to focal and/or weak CK7 expression in the CCRCC-like areas. CD10, α-methylacyl-CoA-racemase, high-molecular-weight cytokeratin, and carbonic anhydrase IX (CA IX) had no significant differential expression between these foci. No cup-like staining pattern was seen with CA IX. Two (11%) patients with pattern 1 tumors developed metastases, and 1 (5%) subsequently died of disease. Eleven (61%) pattern 2 cases had the International Society of Urological Pathology grade 3 nuclei in the CCRCC-like areas, and 7 (39%) were grade 4 (4 of these cases had rhabdoid features; 1 was also sarcomatoid). Of the 16 immunostained pattern 2 tumors, 8 (50%) showed strong diffuse CK7 expression in the CCPRCC-like areas, and 9 (56%) showed complete lack of CK7 expression in the CCRCC-like areas. CD10, α-methylacyl-CoA-racemase, and high-molecular-weight cytokeratin did not have significant differential expression. Membranous expression of CA IX, typically strong and diffuse, was identified in both the CCPRCC-like and CCRCC-like areas in all cases tested (with a cup-like pattern at least focally in the CCPRCC-like areas of 10 [63%] pattern 2 cases). Five (28%) patients with pattern 2 tumors had distant metastases, 3 (17%) of whom subsequently died of disease. Renal cell carcinomas with areas resembling both CCRCC and CCPRCC occur. Some can have high-grade and high-stage foci, and aggressive clinical outcomes are seen. Given this malignant potential, we would presently diagnose such cases as CCRCC. These 2 patterns of renal neoplasia underscore the need for caution in diagnosing CCPRCC on limited sampling, reserving the diagnosis for those tumors that strictly fulfill both morphologic and immunohistochemical criteria.

MicroRNAs in Lymphoma: Regulatory Role and Biomarker Potential

Although it is now evident that microRNAs (miRNAs) play a critical regulatory role in many, if not all, pathological and physiological processes, remarkably they have only formally been recognized for less than fifteen years. These endogenously produced short non-coding RNAs have created a new paradigm of gene control and have utility as both novel biomarkers of cancer and as potential therapeutics. In this review we consider the role of miRNAs in lymphoid biology both under physiological (i.e. lymphopoiesis) and malignant (i.e. lymphomagenesis) conditions. In addition to the functional significance of aberrant miRNA expression in lymphomas we discuss their use as novel biomarkers, both as a in situ tumour biomarker and as a non-invasive surrogate for the tumour by testing miRNAs in the blood of patients. Finally we consider the use of these molecules as potential therapeutic agents for lymphoma (and other cancer) patients and discuss some of the hurdles yet to be overcome in order to translate this potential into clinical practice

Molecular genetics and immunohistochemistry characterization of uncommon and recently described renal cell carcinomas

Renal cell carcinoma (RCC) compromises multiple types and has been emerging dramatically over the recent several decades. Advances and consensus have been achieved targeting common RCCs, such as clear cell carcinoma, papillary RCC and chromophobe RCC. Nevertheless, little is known on the characteristics of several newly-identified RCCs, including clear cell (tubulo) papillary RCC, Xp11 translocation RCC, t(6;11) RCC, succinate dehydrogenase (SDH)-deficient RCC, acquired cystic disease-associated RCC, hereditary leiomyomatosis RCC syndrome-associated RCC, ALK translocation RCC, thyroid-like follicular RCC, tubulocystic RCC and hybrid oncocytic/chromophobe tumors (HOCT). In current review, we will collect available literature of these newly-described RCCs, analyze their clinical pathologic characteristics, discuss their morphologic and immunohistologic features, and finally summarize their molecular and genetic evidences. We expect this review would be beneficial for the understanding of RCCs, and eventually promote clinical management strategies.

Snail heterogeneity in clear cell renal cell carcinoma

Background

Intratumor heterogeneity may be responsible of the unpredictable aggressive clinical behavior that some clear cell renal cell carcinomas display. This clinical uncertainty may be caused by insufficient sampling, leaving out of histological analysis foci of high grade tumor areas. Although molecular approaches are providing important information on renal intratumor heterogeneity, a focus on this topic from the practicing pathologist’ perspective is still pending.

Methods

Four distant tumor areas of 40 organ-confined clear cell renal cell carcinomas were selected for histopathological and immunohistochemical evaluation. Tumor size, cell type (clear/granular), Fuhrman’s grade, Staging, as well as immunostaining with Snail, ZEB1, Twist, Vimentin, E-cadherin, β-catenin, PTEN, p-Akt, p110α, and SETD2, were analyzed for intratumor heterogeneity using a classification and regression tree algorithm.

Results

Cell type and Fuhrman’s grade were heterogeneous in 12.5 and 60 % of the tumors, respectively. If cell type was homogeneous (clear cell) then the tumors were low-grade in 88.57 % of cases. Immunostaining heterogeneity was significant in the series and oscillated between 15 % for p110α and 80 % for Snail. When Snail immunostaining was homogeneous the tumor was histologically homogeneous in 100 % of cases. If Snail was heterogeneous, the tumor was heterogeneous in 75 % of the cases. Average tumor diameter was 4.3 cm. Tumors larger than 3.7 cm were heterogeneous for Vimentin immunostaining in 72.5 % of cases. Tumors displaying negative immunostaining for both ZEB1 and Twist were low grade in 100 % of the cases.

Conclusions

Intratumor heterogeneity is a common event in clear cell renal cell carcinoma, which can be monitored by immunohistochemistry in routine practice. Snail seems to be particularly useful in the identification of intratumor heterogeneity. The suitability of current sampling protocols in renal cancer is discussed.

Do Clear Cell Papillary Renal Cell Carcinomas Have Malignant Potential?

There have been no recurrences or metastases of clear cell papillary renal cell carcinoma (CCPRCC) in 268 reported cases with follow-up in the English-language literature. We identified all our cases of CCPRCC (1990 to 2013), reviewing all cases that preceded the formal designation of the entity. Immunohistochemical stains were performed on 32 cases during their initial workup. In addition, stains for carbonic anhydrase IX and cytokeratin 7 were performed on 2 cases, one with atypical follow-up and the other with a more compact morphology, although not performed initially. An extended panel with AMACR, CD10, and renal cell carcinoma (RCC) was added to the case with atypical follow-up. Fluorescence in situ hybridization for chromosomes 3p, 7, and 17 was performed on the latter case and on another clinically presumed metastatic tumor. In classic cases, immunohistochemical staining was not performed. Fifty-eight patients (31 women; 27 men) with follow-up data were included in our study; 39 cases were from our consult service. The patients' ages ranged from 36 to 83 years. Thirty-five patients had cystic or partially cystic lesions; 6 tumors were multifocal, 3 of which were bilateral. The majority (53 patients; 91.4%) presented with stage pT1 disease (size range, 0.2 to 8 cm), 2 patients presented with pT2 disease (8.5 and 10.3 cm), 1 patient presented with pT3 disease (6.5 cm sarcomatoid RCC focally extending out of the kidney), and pathologic stage was unavailable in 2 cases. Treatment consisted of 29 partial nephrectomies, 26 radical nephrectomies, 2 cryoablations, and 1 cyst ablation. The resection margins were negative in all but one case, with this case disease free after a 26-month period. Two patients had intraoperative tumor disruption and were disease free at 9 and 34 months. Five patients had synchronous ipsilateral renal cell carcinomas (non-CCPRCC). Mean follow-up time was 21 months (range, 1 to 175 mo), with all but 3 patients having no evidence of disease. One patient was presumed to have contralateral disease on the basis of imaging findings and is alive and well 37 months after multiple partial nephrectomies. Metastatic disease to the lung was clinically presumed in 1 patient in whom a higher-grade lesion may have been missed during sampling of the predominantly cystic pT1b tumor and tissue confirmation of the metastases was not obtained. Another case presented with multiple skeletal and pulmonary metastases 8 months after resection of pT3 sarcomatoid CCPRCC. The patient with the sarcomatoid RCC died of multifocal skeletal and pulmonary metastatic disease 13 months after resection of the renal tumor. Our study, the largest to date with follow-up, along with others, suggests that pure CCPRCC is an indolent tumor and should be renamed "clear cell papillary neoplasm of low malignant potential" to reflect their biology.

Intratumor heterogeneity in clear cell renal cell carcinoma: a review for the practicing pathologist

Intertumor heterogeneity, defined as the spectrum of morphological differences found in similar tumors in different patients, is a well-known event for pathologists. However, recent molecular studies have pointed to intratumor heterogeneity as one of the most important issues in human neoplasia in the next years. Clear cell renal cell carcinoma is an example of an intrinsically heterogeneous neoplasm, and some of the most salient advances in the knowledge of intratumor heterogeneity have been developed on it. This review intends to analyze this phenomenon in this tumor from the practicing pathologist's point of view. A careful study of the surgical specimen and an exhaustive tumor sampling are mandatory to keep relevant information. Currently accepted protocols designed for renal tumor sampling may be insufficient. As a result, a different approach to tumor sampling is advisable to ascertain that intratumor heterogeneity, if present, will be well represented in the selected material.

Clear cell papillary renal cell carcinoma as part of histologically discordant multifocal renal cell carcinoma: A case report and review of literature

BACKGROUND

Multifocal renal cell carcinoma of different histological subtypes within a single kidney is rare. We report a recently classified clear cell (tubulo) papillary renal cell carcinoma as part of an unusual case of multifocal renal cell carcinoma of discordant histological subtypes.

RESULTS

A 57 year-old-man was found to have multiple renal tumors and cysts on imaging and underwent a laparoscopic left radical nephrectomy. Pathological review showed multifocal renal cell carcinoma (clear cell (tubulo) papillary, clear cell and papillary renal cell carcinomas and papillary adenomas). Morphology of clear cell papillary renal cell carcinoma was supported by immunohistochemical profile (CK7+, HMWK+, CAIX+, AMACR-, CD10-, TFE3-).

CONCLUSIONS

This is the first report of clear cell papillary renal cell carcinoma as part of multifocal renal cell carcinoma of different histological subtypes. Related lineage of clear cell renal cell carcinoma and papillary renal cell carcinoma is supported by the highest prevalence of their combination within multifocal renal cell carcinoma of different histological subtypes along with their molecular interconnection. Clear cell papillary renal cell carcinoma may be uniquely placed between clear cell and papillary renal cell carcinomas since it shows morphological features intermediate between clear cell and papillary renal cell carcinoma along with overlapping but unique immunohistochemical profile. Clear cell papillary renal cell carcinoma may be molecularly related to clear cell and papillary renal cell carcinomas since the tumors overexpress markers of HIF pathway activation with normal/elevated VHL mRNA expression and some tumors show losses of chromosome 3. Due to the overlapping morphology, it is possible that cases of clear cell papillary renal cell carcinoma may have been misclassified as papillary or clear cell renal cell carcinoma in the literature, incorrectly increasing their reported prevalence. Identification of multifocal RCCs may be related to the extent of pathological sampling.

Clear cell papillary renal cell carcinoma and renal angiomyoadenomatous tumor: two variants of a morphologic, immunohistochemical, and genetic distinct entity of renal cell carcinoma

Clear cell papillary renal cell carcinoma (ccpRCC) and renal angiomyoadenomatous tumor (RAT) share morphologic similarities with clear cell (ccRCC) and papillary RCC (pRCC). It is a matter of controversy whether their morphologic, immunophenotypic, and molecular features allow the definition of a separate renal carcinoma entity. The aim of our project was to investigate specific renal immunohistochemical biomarkers involved in the hypoxia-inducible factor pathway and mutations in the VHL gene to clarify the relationship between ccpRCC and RAT. We investigated 28 ccpRCC and 9 RAT samples by immunohistochemistry using 25 markers. VHL gene mutations and allele losses were investigated by Sanger sequencing and fluorescence in situ hybridization. Clinical follow-up data were obtained for a subset of the patients. No tumor recurrence or tumor-related death was observed in any of the patients. Immunohistochemistry and molecular analyses led to the reclassification of 3 tumors as ccRCC and TFE3 translocation carcinomas. The immunohistochemical profile of ccpRCC and RAT samples was very similar but not identical, differing from both ccRCC and pRCC. Especially, the parafibromin and hKIM-1 expression exhibited differences in ccpRCC/RAT compared with ccRCC and pRCC. Genetic analysis revealed VHL mutations in 2/27 (7%) and 1/7 (14%) ccpRCC and RAT samples, respectively. Fluorescence in situ hybridization analysis disclosed a 3p loss in 2/20 (10%) ccpRCC samples. ccpRCC and RAT have a specific morphologic and immunohistochemical profile, but they share similarities with the more aggressive renal tumors. On the basis of our results, we regard ccpRCC/RAT as a distinct entity of RCCs.

The evolving classification of renal cell neoplasia

The classification of renal cell neoplasia is morphologically based; however, this has evolved over the last 35 years with the incorporation of genetic characteristics into the diagnostic features of some tumors. The 2013 Vancouver classification recognized 17 morphotypes of renal parenchymal malignancy and two benign tumors. This classification included the newly established entities tubulocystic renal cell carcinoma (RCC)), acquired cystic disease-associated RCC, clear cell (tubulo) papillary RCC, microphthalmia transcription factor family translocation RCC and hereditary leiomyomatosis RCC syndrome-associated RCC. In addition to these newly described forms of RCC there are a number of novel tumors that are currently recognized as emerging entities. These are likely to be incorporated into subsequent classifications and include thyroid-like follicular RCC, succinate dehydrogenase B mutation-associated RCC, ALK translocation RCC, tuberous sclerosis complex-associated RCC, and RCC with (angio) leiomyomatous stroma.

Clear cell papillary renal cell carcinoma: micro-RNA expression profiling and comparison with clear cell renal cell carcinoma and papillary renal cell carcinoma

Clear cell papillary renal cell carcinoma (CCPRCC) is a low-grade renal neoplasm with morphological characteristics mimicking both clear cell renal cell carcinoma (CCRCC) and papillary renal cell carcinoma (PRCC). However, despite some overlapping features, their morphological, immunohistochemical, and molecular profiles are distinct. Micro-RNAs (miRNAs) are small noncoding RNAs that play a crucial role in regulating gene expression and are involved in various biological processes, including cancer development. To better understand the biology of this tumor, we aimed to analyze the miRNA expression profile of a set of CCPRCC using microarray and quantitative reverse transcription-polymerase chain reaction. A total of 15 cases diagnosed as CCPRCC were used in this study. Among the most differentially expressed miRNA in CCPRCC, we found miR-210, miR-122, miR-34a, miR-21, miR-34b*, and miR-489 to be up-regulated, whereas miR-4284, miR-1202, miR-135a, miR-1973, and miR-204 were down-regulated compared with normal renal parenchyma. To identify consensus of differentially regulated miRNA between CCPRCC, CCRCC, and PRCC, we additionally determined differential miRNA expression using 2 publically available microarray data sets from the NCBI Gene Expression Omnibus database (GSE41282 and GSE3798). This comparison revealed that the miRNA expression profile of CCPRCC shows some overlapping characteristics between CCRCC and PRCC. Moreover, CCPRCC lacks dysregulation of important miRNAs typically associated with aggressive behavior. In summary, we describe the miRNA expression profile of a relatively infrequent type of renal cancer. Our results may help in understanding the molecular underpinning of this newly recognized entity.