Chromosomal gains in the sarcomatoid transformation of chromophobe renal cell carcinoma

Chromophobe Renal Cell Carcinoma with Sarcomatoid Differentiation: Clinicopathologic Correlation and Molecular Findings

Introduction: Sarcomatoid differentiation has been reported in approximately 8% of chromophobe renal cell carcinoma (RCC) and is associated with a worse prognosis. We aim to describe the clinicopathologic and molecular findings of chromophobe RCC with sarcomatoid differentiation. Methods: Surgical pathology database was searched to identify chromophobe RCC with sarcomatoid differentiation from January 2015 to December 2021. Results: Five patients were diagnosed with chromophobe RCC with sarcomatoid differentiation. The median age at the time of diagnosis was 57 years (range 51-61 years). Three patients died after median follow-up of 12.1 months (range 1.6-18.2 months). The median tumor size was 10.7 cm (range 5.6-13.6 cm). The median percentage of sarcomatoid component was 60% (range 10-90%), and the median percentage of necrosis was 30% (range 10-50%). One tumor demonstrated osteoid formation. PAX8, keratin 7, KIT (CD117), and Hale colloidal iron were positive in the epithelial component, whereas the sarcomatoid component was positive for vimentin, CD10, and high Ki67 proliferative index. Molecular testing was performed in three specimens: all were TP53 mutated and microsatellite stable. One aggressive tumor had RB1 frameshift mutation and copy number gains for TERT and CUL4A. Conclusion: Chromophobe RCC with sarcomatoid differentiation is a rare entity with aggressive behavior. Percentage of sarcomatoid component, necrosis, and the occurrence of metastasis is associated with worse prognosis. Molecular profiling reveals frequent TP53 mutation. While TERT promoter mutation has no prognostic implication, FLCN inactivation may be associated with a less aggressive course. The clinical significance of RB1 loss is unclear.

Characterization of Intercalated Cell Markers KIT and LINC01187 in Chromophobe Renal Cell Carcinoma and Other Renal Neoplasms

Introduction. Chromophobe renal cell carcinoma (chromophobe RCC) is the third major subcategory of renal tumors after clear cell RCC and papillary RCC, accounting for approximately 5% of all RCC subtypes. Other oncocytic neoplasms seen commonly in surgical pathology practice include the eosinophilic variant of chromophobe RCC, renal oncocytoma, and low-grade oncocytic unclassified RCC. Methods. In our recent next-generation sequencing based study, we nominated a lineage-specific novel biomarker LINC01187 (long intergenic non-protein coding RNA 1187) which was found to be enriched in chromophobe RCC. Like KIT (cluster of differentiation 117; CD117), a clinically utilized chromophobe RCC related biomarker, LINC01187 is expressed in intercalated cells of the nephron. In this follow-up study, we performed KIT immunohistochemistry and LINC01187 RNA in situ hybridization (RNA-ISH) on a cohort of chromophobe RCC and other renal neoplasms, characterized the expression patterns, and quantified the expression signals of the two biomarkers in both primary and metastatic settings. Results. LINC01187, in comparison to KIT, exhibits stronger and more uniform expression within tumors while maintaining temporal and spatial consistency. LINC01187 also is devoid of intra-tumoral heterogeneous expression pattern, a phenomenon commonly noted with KIT. Conclusions. LINC01187 expression can augment the currently utilized KIT assay and help facilitate easy microscopic analyses in routine surgical pathology practice.

Chromophobe renal cell carcinoma with sarcomatoid and heterologous osteosarcoma-like differentiation: a case report and literature review

Chromophobe renal cell carcinoma (CRCC) is a subtype of renal cell carcinoma (RCC) with a favorable prognosis. Sarcomatoid differentiation in RCC is assumed to be the outcome of the parent tumor's dedifferentiation and associated with poorer prognosis. Sarcomatoid differentiation can be detected in CRCC as well as other subtypes, but the occurrence of divergent osteosarcoma-like components in sarcomatoid CRCC is extremely unusual. Only six cases have been previously reported in the literature, we reviewed them and presented the seventh case in a 71-year-old male who had a left kidney heterogeneous mass. The resected tumor showed a sarcoma-like spindle cell area with an adjacent osteosarcoma area producing lacy bone material and bony trabeculae in a hard area mixed with a typical CRCC. In conclusion, sarcomatoid CRCC with osteosarcomatous differentiation is a very rare tumor and should be kept in mind especially when dealing with small or frozen sections biopsies.

New developments in existing WHO entities and evolving molecular concepts: The Genitourinary Pathology Society (GUPS) update on renal neoplasia

The Genitourinary Pathology Society (GUPS) reviewed recent advances in renal neoplasia, particularly post-2016 World Health Organization (WHO) classification, to provide an update on existing entities, including diagnostic criteria, molecular correlates, and updated nomenclature. Key prognostic features for clear cell renal cell carcinoma (RCC) remain WHO/ISUP grade, AJCC/pTNM stage, coagulative necrosis, and rhabdoid and sarcomatoid differentiation. Accrual of subclonal genetic alterations in clear cell RCC including SETD2, PBRM1, BAP1, loss of chromosome 14q and 9p are associated with variable prognosis, patterns of metastasis, and vulnerability to therapies. Recent National Comprehensive Cancer Network (NCCN) guidelines increasingly adopt immunotherapeutic agents in advanced RCC, including RCC with rhabdoid and sarcomatoid changes. Papillary RCC subtyping is no longer recommended, as WHO/ISUP grade and tumor architecture better predict outcome. New papillary RCC variants/patterns include biphasic, solid, Warthin-like, and papillary renal neoplasm with reverse polarity. For tumors with 'borderline' features between oncocytoma and chromophobe RCC, a term "oncocytic renal neoplasm of low malignant potential, not further classified" is proposed. Clear cell papillary RCC may warrant reclassification as a tumor of low malignant potential. Tubulocystic RCC should only be diagnosed when morphologically pure. MiTF family translocation RCCs exhibit varied morphologic patterns and fusion partners. TFEB-amplified RCC occurs in older patients and is associated with more aggressive behavior. Acquired cystic disease (ACD) RCC-like cysts are likely precursors of ACD-RCC. The diagnosis of renal medullary carcinoma requires a negative SMARCB1 (INI-1) expression and sickle cell trait/disease. Mucinous tubular and spindle cell carcinoma (MTSCC) can be distinguished from papillary RCC with overlapping morphology by losses of chromosomes 1, 4, 6, 8, 9, 13, 14, 15, and 22. MTSCC with adverse histologic features shows frequent CDKN2A/2B (9p) deletions. BRAF mutations unify the metanephric family of tumors. The term "fumarate hydratase deficient RCC" ("FH-deficient RCC") is preferred over "hereditary leiomyomatosis and RCC syndrome-associated RCC". A low threshold for FH, 2SC, and SDHB immunohistochemistry is recommended in difficult to classify RCCs, particularly those with eosinophilic morphology, occurring in younger patients. Current evidence does not support existence of a unique tumor subtype occurring after chemotherapy/radiation in early childhood.

Comprehensive Review of Numerical Chromosomal Aberrations in Chromophobe Renal Cell Carcinoma Including Its Variant Morphologies

Chromophobe renal cell carcinoma (ChRCC) accounts for 5% to 7% of all renal cell carcinomas. It was thought for many years that ChRCC exhibits a hypodiploid genome. Recent studies using advanced molecular genetics techniques have shown more complex and heterogenous pattern with frequent chromosomal gains. Historically, multiple losses of chromosomes 1, 2, 6, 10, 13, 17, and 21 have been considered a genetic hallmark of ChRCC, both for classic and eosinophilic ChRCC variants. In the last 2 decades, multiple chromosomal gains in ChRCCs have also been documented, depicting a considerably broader genetic spectrum than previously thought. Studies of rare morphologic variants including ChRCC with pigmented microcystic adenomatoid/multicystic growth, ChRCC with neuroendocrine differentiation, ChRCC with papillary architecture, and renal oncocytoma-like variants also showed variable chromosomal numerical aberrations, including multiple losses (common), gains (less common), or chromosomal changes overlapping with renal oncocytoma. Although not the focus of the review, The Cancer Genome Atlas (TCGA) data in ChRCC show TP53, PTEN, and CDKN2A to be the most mutated genes. Given the complexity of molecular genetic alterations in ChRCC, this review analyzed the existing published data, aiming to present a comprehensive up-to-date survey of the chromosomal abnormalities in classic ChRCC and its variants. The potential role of chromosomal numerical aberrations in the differential diagnostic evaluation may be limited, potentially owing to its high variability.

Genetic Alterations in Renal Cancers: Identification of The Mechanisms Underlying Cancer Initiation and Progression and of Therapeutic Targets

Renal cell cancer (RCC) involves three most recurrent sporadic types: clear-cell RCC (70-75%, CCRCC), papillary RCCC (10-15%, PRCC), and chromophobe RCC (5%, CHRCC). Hereditary cases account for about 5% of all cases of RCC and are caused by germline pathogenic variants. Herein, we review how a better understanding of the molecular biology of RCCs has driven the inception of new diagnostic and therapeutic approaches. Genomic research has identified relevant genetic alterations associated with each RCC subtype. Molecular studies have clearly shown that CCRCC is universally initiated by Von Hippel Lindau (VHL) gene dysregulation, followed by different types of additional genetic events involving epigenetic regulatory genes, dictating disease progression, aggressiveness, and differential response to treatments. The understanding of the molecular mechanisms that underlie the development and progression of RCC has considerably expanded treatment options; genomic data might guide treatment options by enabling patients to be matched with therapeutics that specifically target the genetic alterations present in their tumors. These new targeted treatments have led to a moderate improvement of the survival of metastatic RCC patients. Ongoing studies based on the combination of immunotherapeutic agents (immune check inhibitors) with VEGF inhibitors are expected to further improve the survival of these patients.

Detection of tetraploidization in chromophobe renal cell carcinoma: Insights and pitfalls

Chromosomal losses resulting in a marked hypodiploidy are a specificity of chromophobe renal cell carcinoma (ChRCC), the third most frequent type of kidney cancer. Its detection is useful in challenging cases. However some ChRCC, especially the eosinophilic variant, do not exhibit hypodiploidy and deserve to be better explored. Using comparative genomic hybridization (array-CGH) we observed chromosomal gains in five cases of nonmetastatic ChRCC. Our objective was to determine whether these apparent chromosomal gains were instead losses within a near-polyploid genome. We performed a retrospective and prospective molecular study of 26 cases of ChRCC retrieved among 643 renal tumors (2012-2019). All tumors were analyzed using array-CGH (Agilent) and array-CGH (Affymetrix) coupled to single nucleotide polymorphism analysis (array-SNP). In silico manual centralization of the fluorescence ratio, fluorescence in situ hybridization (FISH) and next generation sequencing were made in the five cases suspected of polyploidy. Tetraploidization was observed in 19% of our series of ChRCC. None of the methods used individually could identify both chromosomal losses and tetraploidy. Only the combination of manual recentring of array-CGH and FISH provided relevant results. B-allele frequency results indicated that tetraploidization occurred secondarily to chromosomal losses in four cases while it preceded losses in one case. Tetraploidization is a frequent but underestimated phenomenon in ChRCC that may be overlooked using the individual standard genomic methods. Its potential clinical consequences are not identified yet. Whether the mechanisms that induce chromosomal losses in ChRCC are the same that generate tetraploidization is not known.

Systemic therapy for chromophobe renal cell carcinoma: A systematic review

BACKGROUND

Chromophobe renal cell carcinoma (chRCC) subtype accounts for almost 5% of total RCC cases. It carries the best prognosis among the rest of RCC types. However, patients with metastatic chRCC disease have worse prognosis than patients with advanced clear cell RCC. Furthermore, available data regarding systemic therapy for chRCC patients are scarce and confusing.

AIM

The aim of this systematic review is to search for and critically appraise studies that investigate the results of systemic therapies in patients diagnosed with metastatic chRCC disease.

METHODS

Search strategy included PUBMED, CENTRAL, clinicaltrials.gov databases, and abstracts of major conferences with a focus on urologic oncology (till March 2019). Studies investigating patients that were treated with systemic therapy for advanced chRCC disease were included. Primary outcomes were progression-free survival and objective response rate. Secondary outcome was overall survival. Screening of available studies was carried out by 2 groups of reviewers, as well as the quality assessment of the included studies.

RESULTS

The systematic search yielded 369 studies, of which 15 studies (2 randomized control trials and 13 cohort studies), involving 183 patients, met the eligibility criteria. The 2 randomized control trials that directly compared sunitinib vs. everolimus, suggested an advantage for sunitinib without being statistically significant. Furthermore, sunitinib seems to be superior than sorafenib at least in terms of objective response rate. Regarding mTOR inhibitors, they may have a role in a specific subset of chRCC patients, that needs to be further explored. Finally, as far as immunotherapy is concerned, available data suggest that chRCC seems to be resistant to recent immune check point inhibitors, since just a few tumor responses were observed with the administered immunotherapy regiments.

CONCLUSION

The optimum therapy for metastatic chRCC is still missing, as results from ongoing trials are awaited. More studies, of high quality and adequate sample size, that will be based on the specific biology of chRCC, have to be carried out in order to identify the best treatment.

Immunotherapy in renal cell carcinoma from poverty to the spoiled of choice

Management of metastatic renal cell carcinoma has been enriched by the advent of new therapeutic compounds. The approval of new combination strategies between targeted agents and immune-checkpoint inhibitors as well as the administration of combinations between immune-checkpoint inhibitors has clearly demonstrated significant improvement toward patients' prognosis and other clinical outcomes. Due to the availability of different treatments, the choice between them may be a difficult issue in our clinical practice. We have summarized current knowledge about available treatments focusing on criteria, which may help clinicians to make decisions.

Toward a genome-based treatment landscape for renal cell carcinoma

Knowledge about molecular mechanisms driving development and progression of renal cell carcinoma has been elucidated by different studies. In few years we discovered a large difference between genomic landscapes of clear cell and non-clear cell carcinoma. Moreover, tumor heterogeneity and different acquisition of gene mutations during tumor progression are issues of particular interest. In this review we focalized our attention on principal genomic alterations identified among RCC subtypes. Acquired gene mutations may be an adaptive response to several external pressure including metabolic, treatment, genomic and immune-related external pressure. Thus we correlated and discussed principal genomic alterations adopted by tumor to escape from each external pressures. The aim of the present work is to summarize current knowledge about genomic alterations in RCC with special interest of treatment strategies tailored on the basis of disease mutations assessment.

Grading of renal cell carcinoma

Grading of renal cell carcinoma (RCC) has been recognised as a prognostic factor for almost 100 years. Numerous grading systems have been proposed, initially focusing upon a constellation of cytological features and more recently on nuclear morphology. It has been recommended that grading of RCC should be based upon nucleolar prominence/eosinophilia for grades 1-3, while grade 4 requires nuclear anaplasia (including tumour giant cells, sarcomatoid differentiation and/or rhabdoid morphology). The grading system was adopted formally by the International Society of Urological Pathology (ISUP) and subsequently by the World Health Organisation (WHO), being designated the WHO/ISUP grading classification in the fourth edition of the WHO classification tumours of the urinary system and male genital organs (2016). This grading system has been validated for both clear cell and papillary RCC. Validation studies for chromophobe RCC failed to demonstrate a correlation between grade and outcome for both the superseded Fuhrman grading system and the WHO/ISUP grading classification, and it has been recommended that these tumours not be graded. The WHO/ISUP system has been incorporated into the structured reports of the International Cancer Collaboration on Cancer Reporting for both clear cell and papillary RCC. It is also noted that other types of RCC may be graded, but it must be emphasised in the report that this is for descriptive and diagnostic purposes, and not outcome prediction. More recent studies have shown the incorporation of the presence of tumour necrosis into RCC grading to improve outcome prediction, and this has been validated in several studies.

Variation in nuclear size and PD-L2 positivity correlate with aggressive chromophobe renal cell carcinoma

Chromophobe renal cell carcinoma (CRCC) is not amenable to International Society for Urologic Pathology-endorsed nucleolar grading. Novel grading approaches were proposed, but the rarity of adverse pathology hampers their discriminatory value. We investigate simple linear micrometer measurements and a proposed immunostain in CRCCs. 32 patients' CRCCs were studied: 12 adverse cases (stage pT3, recurrence, or metastasis), 15 controls (stage ≤pT2, no recurrence or metastasis after >3 years), and 8 metastases (3 were paired with primary adverse cases). The ratio of greatest dimensions of largest and smallest nuclei, in each of 5 "worst" high-power fields, excluding those with degenerative features, was designated variation in nuclear size (VNS). Percent multinucleate cells (PMC) were also counted. Mouse anti PD-L2 monoclonal antibody immunostaining was performed. Mean VNS measured in adverse primary and control primary tumors were 3.7 ± 0.5 and 2.4 ± 0.4 respectively (P < .001), and 3.4 ± 0.4 for metastases (P < .001). Optimal VNS cut-off was 2.5, with sensitivity and specificity 0.85 and 0.81, respectively. PMCs were 6.0 ± 3.0 for adverse group, 5.7 ± 2.7 for controls, and 4.1 ± 1.6 for metastases (P = NS). PD-L2 could not discriminate adverse versus good primary tumors (χ²1.6, P = .2), but was higher in metastases (χ² 6.9, P < .01), or metastases plus adverse primary tumors (χ² 4.8, P = .03), compared to good-pathology primary tumors. In conclusion, VNS is an easily obtained measurement that can predict adverse behavior of chromophobe RCC, and may impart value for needle biopsy reporting and the choice of active surveillance. PD-L2 was elevated in metastases but was less useful for primary tumors.

Genomic and metabolic characterization of a chromophobe renal cell carcinoma cell line model (UOK276)

Chromophobe renal cell carcinoma (ChRCC) represents 5% of all RCC cases and frequently demonstrates multiple chromosomal losses and an indolent pattern of local growth, but can demonstrate aggressive features and resistance to treatment in a metastatic setting. Cell line models are an important tool for the investigation of tumor biology and therapeutic drug efficacy. Currently, there are few ChRCC-derived cell lines and none is well characterized. This study characterizes a novel ChRCC-derived cell line model, UOK276. A large ChRCC tumor with regions of sarcomatoid differentiation was used to establish a spontaneously immortal cell line, UOK276. UOK276 was evaluated for chromosomal, mutational, and metabolic aberrations. The UOK276 cell line is hyperdiploid with a modal number of 49 chromosomes per cell, and evidence of copy-neutral loss of heterozygosity, as opposed to the classic pattern of ChRCC chromosomal losses. UOK276 demonstrated a TP53 missense mutation, expressed mutant TP53 protein, and responded to treatment with a small-molecule therapeutic agent, NSC319726, designed to reactivate mutated TP53. Xenograft tumors grew in nude mice and provide an in vivo animal model for the investigation of potential therapeutic regimes. The xenograft pathology and genetic analysis suggested that UOK276 was derived from the sarcomatoid region of the original tumor. In summary, UOK276 represents a novel in vitro and in vivo cell line model for aggressive, sarcomatoid-differentiated, TP53 mutant ChRCC. This preclinical model system could be used to investigate the novel biology of aggressive, sarcomatoid ChRCC and evaluate the new therapeutic regimes.

Papillary Renal Cell Carcinoma With Osteosarcomatous Heterologous Differentiation: A Case Report With Molecular Genetic Analysis and Review of the Literature

Sarcomatoid differentiation can occur in all subtypes of renal cell carcinoma (RCC). In rare cases, heterologous differentiation has been described. We present a case of heterologous osteosarcomatous differentiation in association with sarcomatoid papillary RCC including an analysis of chromosomal copy number alteration. This is the first case to identify heterologous differentiation in association with papillary RCC. The patient was a 70-year-old man who had a mass in the right kidney. Speckled calcification was seen on computed tomography scan. Histological assessment demonstrated papillary RCC merging with areas of sarcomatoid change and malignant bone formation simulating osteosarcoma. Cytogenetic evaluation demonstrated additional copies of chromosome 7 in both epithelial and osteosarcomatous components. A literature review identified 33 previous cases of heterologous differentiation in association with RCC. Of the 14 cases that reported an epithelial subtype, 13 cases were reported to be chromophobe RCC and 1 case was reported to be clear cell RCC.

Genomic landscape and evolution of metastatic chromophobe renal cell carcinoma

Chromophobe renal cell carcinoma (chRCC) typically shows ~7 chromosome losses (1, 2, 6, 10, 13, 17, and 21) and ~31 exonic somatic mutations, yet carries ~5%-10% metastatic incidence. Since extensive chromosomal losses can generate proteotoxic stress and compromise cellular proliferation, it is intriguing how chRCC, a tumor with extensive chromosome losses and a low number of somatic mutations, can develop lethal metastases. Genomic features distinguishing metastatic from nonmetastatic chRCC are unknown. An integrated approach, including whole-genome sequencing (WGS), targeted ultradeep cancer gene sequencing, and chromosome analyses (FACETS, OncoScan, and FISH), was performed on 79 chRCC patients including 38 metastatic (M-chRCC) cases. We demonstrate that TP53 mutations (58%), PTEN mutations (24%), and imbalanced chromosome duplication (ICD, duplication of ≥ 3 chromosomes) (25%) were enriched in M-chRCC. Reconstruction of the subclonal composition of paired primary-metastatic chRCC tumors supports the role of TP53, PTEN, and ICD in metastatic evolution. Finally, the presence of these 3 genomic features in primary tumors of both The Cancer Genome Atlas kidney chromophobe (KICH) (n = 64) and M-chRCC (n = 35) cohorts was associated with worse survival. In summary, our study provides genomic insights into the metastatic progression of chRCC and identifies TP53 mutations, PTEN mutations, and ICD as high-risk features.

The Pathology and Molecular Genetics of Sarcomatoid Renal Cell Carcinoma: A Mini-Review

Sarcomatoid renal cell carcinoma is a highly aggressive tumor. It is not a distinct histologic entity as it can be found in any subtypes of renal cell carcinoma. Recent molecular and genetic evidence suggest that sarcomatoid component is transformed from a common progenitor of the associated renal cell carcinoma, and the TP53 gene plays a pivotal role in this process. The presence of sarcomatoid carcinoma indicates poor prognosis, which also correlates with the amount of the sarcomatoid component. Therefore, the presence and quantity of sarcomatoid component should be reflected in pathology reports. However, pathology reporting seems to vary among laboratories prompting the need for a unified reporting system. We propose a pathology reporting system similar to that of transformed follicular lymphoma that is consistent with the molecular pathogenesis to ensure uniform reporting.

Morphological, immunohistochemical, and chromosomal analysis of multicystic chromophobe renal cell carcinoma, an architecturally unusual challenging variant

Chromophobe renal cell carcinoma (ChRCC) is typically composed of large leaf-like cells and smaller eosinophilic cells arranged in a solid-alveolar pattern. Eosinophilic, adenomatoid/pigmented, or neuroendocrine variants have also been described. We collected 10 cases of ChRCC with a distinct multicystic pattern out of 733 ChRCCs from our registry, and subsequently analyzed these by morphology, immunohistochemistry, and array comparative genomic hybridization. Of the 10 patients, 6 were males with an age range of 50-89 years (mean 68, median 69). Tumor size ranged between 1.2 and 20 cm (mean 5.32, median 3). Clinical follow-up was available for seven patients, ranging 1-19 years (mean 7.2, median 2.5). No aggressive behavior was documented. We observed two growth patterns, which were similar in all tumors: (1) variable-sized cysts, resembling multilocular cystic neoplasm of low malignant potential and (2) compressed cystic and tubular pattern with slit-like spaces. Raisinoid nuclei were consistently present while necrosis was absent in all cases. Half of the cases showed eosinophilic/oncocytic cytology, deposits of pigment (lipochrome) and microcalcifications. The other half was composed of pale or mixed cell populations. Immunostains for epithelial membrane antigen (EMA), CK7, OSCAR, CD117, parvalbumin, MIA, and Pax 8 were positive in all tumors while negative for vimentin, TFE3, CANH 9, HMB45, cathepsin K, and AMACR. Ki67 immunostain was positive in up to 1 % of neoplastic cells. Molecular genetic examination revealed multiple chromosomal losses in two fifths analyzable tumors, while three cases showed no chromosomal numerical aberrations. ChRCC are rarely arranged in a prominent multicystic pattern, which is probably an extreme form of the microcystic adenomatoid pigmented variant of ChRCC. The spectrum of tumors entering the differential diagnosis of ChRCC is quite different from that of conventional ChRCC. The immunophenotype of ChRCC is identical with that of conventional ChRCC. Chromosomal numerical aberration pattern was variable; no chromosomal numerical aberrations were found in three cases. All the cases in this series have shown an indolent and non-aggressive behavior.

Flcn-deficient renal cells are tumorigenic and sensitive to mTOR suppression

Deficiency of tumor suppressor FLCN leads to the activation of the mTOR signaling pathway in human BHD-associated renal cell carcinomas (RCC). We have previously developed a renal distal tubule-collecting duct-Henle's loop-specific Flcn knockout (KO) mouse model (Flcn^flox/flox/Ksp-Cre). This mouse model can only survive for three weeks after birth due to the development of polycystic kidney and uremia. Whether these cystic solid hyperplasia changes seen in those KO mice are tumorigenic or malignant is unknown. In this study, we demonstrated that genetic disruption of Flcn in mouse kidney distal tubule cells could lead to tumorigenic transformation of these cells to develop allograft tumors with an aggressive histologic phenotype. Consistent with previous reports, we showed that the mTOR pathway plays an important role in the growth of these Flcn-deficient allograft and human UOK 257-1 xenograft tumors. We further demonstrated that the mTOR inhibitor, sirolimus, suppresses the tumor's growth, suggesting that mTOR inhibitors might be effective in control of FLCN-deficient RCC, especially in BHD renal tumorigenesis.

Genomic Copy Number Alterations in Renal Cell Carcinoma with Sarcomatoid Features

PURPOSE

Sarcomatoid changes in renal cell carcinoma are associated with a poor prognosis. The identification of genetic alterations that drive this aggressive phenotype could aid in the development of more effective targeted therapies. In this study we aimed to pinpoint unique copy number alterations in sarcomatoid renal cell carcinoma compared to classical renal cell carcinoma subtypes.

MATERIALS AND METHODS

Genomic copy number analysis was performed using single nucleotide polymorphism based microarrays on tissue extracted from the tumors of 81 patients who underwent renal mass excision, including 17 with sarcomatoid renal cell carcinoma.

RESULTS

Sarcomatoid renal cell carcinoma showed a significantly higher number of copy number alterations than clear cell, papillary and chromophobe renal cell carcinoma (mean 18.0 vs 5.8, 6.5 and 7.2, respectively, p <0.0001). Copy number losses of chromosome arms 9q, 15q, 18p/q and 22q, and gains of 1q and 8q occurred in a significantly higher proportion of sarcomatoid renal cell carcinomas than in the other 3 histologies. Patients with sarcomatoid renal cell carcinoma demonstrated significantly worse overall survival compared to those without that condition on Kaplan-Meier analysis (p = 0.0001). Patients with 9 or more copy number alterations also demonstrated significantly worse overall survival than those with fewer than 9 copy number alterations (p = 0.004).

CONCLUSIONS

Sarcomatoid changes in renal cell carcinoma are associated with a high rate of chromosomal imbalances with losses of 9q, 15q, 18p/q and 22q, and gains of 1q and 8q occurring at significantly higher frequencies in comparison to nonsarcomatoid renal cell carcinoma. Identifying candidate driver genes or tumor suppressor loci in these chromosomal regions may help identify targets for future therapies.

Genetic and Chromosomal Aberrations and Their Clinical Significance in Renal Neoplasms

The most common form of malignant renal neoplasms is renal cell carcinoma (RCC), which is classified into several different subtypes based on the histomorphological features. However, overlaps in these characteristics may present difficulties in the accurate diagnosis of these subtypes, which have different clinical outcomes. Genomic and molecular studies have revealed unique genetic aberrations in each subtype. Knowledge of these genetic changes in hereditary and sporadic renal neoplasms has given an insight into the various proteins and signalling pathways involved in tumour formation and progression. In this review, the genetic aberrations characteristic to each renal neoplasm subtype are evaluated along with the associated protein products and affected pathways. The potential applications of these genetic aberrations and proteins as diagnostic tools, prognostic markers, or therapeutic targets are also assessed.

Biphasic components of sarcomatoid clear cell renal cell carcinomas are molecularly similar to each other, but distinct from, non-sarcomatoid renal carcinomas

Sarcomatoid transformation, wherein an epithelioid carcinomatous tumour component coexists with a sarcomatoid histology, is a predictor of poor prognosis in clear cell renal cell carcinoma. Our understanding of sarcomatoid change has been hindered by the lack of molecular examination. Thus, we sought to characterize molecularly the biphasic epithelioid and sarcomatoid components of sarcomatoid clear cell renal cell carcinoma and compare them to non-sarcomatoid clear cell renal cell carcinoma. We examined the transcriptome of the epithelioid and sarcomatoid components of advanced stage sarcomatoid clear cell renal cell carcinoma (n=43) and non-sarcomatoid clear cell renal cell carcinoma (n=37) from independent discovery and validation cohorts using the cDNA microarray and RNA-seq platforms. We analyzed DNA copy number profiles, generated using SNP arrays, from patients with sarcomatoid clear cell renal cell carcinoma (n=10) and advanced non-sarcomatoid clear cell renal cell carcinoma (n=155). The epithelioid and sarcomatoid components of sarcomatoid clear cell renal cell carcinoma had similar gene expression and DNA copy number signatures that were, however, distinct from those of high-grade, high-stage non-sarcomatoid clear cell renal cell carcinoma. Prognostic clear cell renal cell carcinoma gene expression profiles were shared by the biphasic components of sarcomatoid clear cell renal cell carcinoma and the sarcomatoid component showed a partial epithelial-to-mesenchymal transition signature. Our genome-scale microarray-based transcript data were validated in an independent set of sarcomatoid and non-sarcomatoid clear cell renal cell carcinomas using RNA-seq. Sarcomatoid clear cell renal cell carcinoma is molecularly distinct from non-sarcomatoid clear cell renal cell carcinoma, with its genetic programming largely shared by its biphasic morphological components. These data explain why a low percentage of sarcomatoid histology augurs a poor prognosis; suggest the need to modify the pathological grading system and introduce the potential for candidate biomarkers to detect sarcomatoid change preoperatively without specifically sampling the histological sarcomatoid component.

Disruption of tubular Flcn expression as a mouse model for renal tumor induction

The study of kidney cancer pathogenesis and its treatment has been limited by the scarcity of genetically defined animal models. The FLCN gene that codes for the protein folliculin, mutated in Birt-Hogg-Dubé syndrome, presents a new target for mouse modeling of kidney cancer. Here we developed a kidney-specific knockout model by disrupting the mouse Flcn in the proximal tubules, thus avoiding homozygous embryonic lethality or neonatal mortality, and eliminating the requirement of loss of heterozygosity for tumorigenesis. This knockout develops renal cysts and early onset (6 months) of multiple histological subtypes of renal neoplasms featuring high tumor penetrance. Although the majority of the tumors were chromophobe renal cell carcinomas in affected mice under 1 year of age, papillary renal cell carcinomas predominated in the kidneys of older knockout mice. This renal neoplasia from cystic hyperplasia at 4 months to high-grade renal tumors by 16 months represented the progression of tumorigenesis. The mTOR and TGF-β signalings were upregulated in Flcn-deficient tumors, and these two activated pathways may synergetically cause renal tumorigenesis. Treatment of knockout mice with the mTOR inhibitor rapamycin for 10 months led to the suppression of tumor growth. Thus, our model recapitulates human Birt-Hogg-Dubé kidney tumorigenesis, provides a valuable tool for further study of Flcn-deficient renal tumorigenesis, and tests new drugs/approaches to their treatment.

Sarcomatoid renal cell carcinoma: case report and review of literature

Sarcomatoid renal cell carcinoma is a tumour with aggressive behaviour. It is a form of dedifferentiated carcinoma with high incidence of metastases to the lungs. We report a case of 55-year-old male who presented with complaints of loin pain and hematuria. The biopsy confirmed sarcomatoid variant of renal cell carcinoma.

Chromophobe renal cell carcinoma with concomitant sarcomatoid transformation and osseous metaplasia: a case report

Background

Chromophobe renal cell carcinoma is the third most common form of adult renal epithelial neoplasm. A sarcomatoid component occurs in approximately 8% of all chromophobe renal cell carcinoma cases, while metaplastic bone formation is extremely rare.

Case presentation

An abdominal computed tomography scan revealed a hypovascular tumor with focal calcification, measuring 2.5 × 2.3 cm, in the upper pole of the right kidney. The tumor was clinically diagnosed as a right renal cell carcinoma that showed signs of calcification, and a laparoscopic right radical nephrectomy was performed. The cut surface of the tumor was beige in color and indicated that the tumor was an extensively ossified mass. Histological analysis revealed three distinct morphological components of the tumor. The chromophobe renal cell carcinoma consisted of compact epithelial cells arranged in a nested pattern, and these were mixed with extensive areas of sarcomatoid spindle cells with marked nuclear pleomorphism and brisk mitotic activity. The tumor also contained multiple foci of metaplastic ossification.

Conclusion

Chromophobe renal cell carcinoma with concomitant osseous metaplasia and sarcomatoid transformation is a very rare occurrence.

Chromophobe renal cell carcinoma--chromosomal aberration variability and its relation to Paner grading system: an array CGH and FISH analysis of 37 cases

Genetically, chromophobe renal cell carcinoma (ChRCC) is characterized by multiple chromosomal changes, especially losses. The most common losses include chromosomes 1, 2, 6, 10, 13, 17, and 21. The Fuhrman grading system lacks prognostic relevance for ChRCC, and recently, a new grading system for ChRCC was proposed by Paner. The objective of this study was to map the spectrum of chromosomal aberrations (extent and location) in a large cohort of ChRCCs and relate these findings to the Paner grading system (PGS). A large cohort of ChRCC was reviewed and graded according to the PGS. All the cases were reevaluated and separated into groups according to their PGS. The final study set was 37 patients. ChRCCs were divided into PG 1-3, sarcomatoid, and aggressive groups. "Aggressive ChRCCs" were designated cases with known metastatic activity, local recurrence, aggressive growth to the adjacent organs, or invasive growth into the renal sinus (with/without angioinvasion). Sarcomatoid tumors were divided into their epithelial and sarcomatoid component (further molecular genetic analyses were performed separately). Array comparative genome hybridization and/or fluorescence in situ hybridization analysis was applied to 42 samples from the 37 cases. Multiple losses, as well as gains, were detected in different chromosomes. Regardless of the PGS groups, the most frequently detected losses involved chromosomes 1 (27/37), 2 (26/37), 6 (23/37), 10 (26/37), 13 (19/37), and 17 (24/37). Loss of chromosome 21 was found in 12/37 cases. The most frequently detected gains were found on chromosomes 4 (22/37), 7 (24/37), 15 (20/37), 19 (22/37), and 20 (21/37). Cluster analysis showed that there is no relation between PGS and particular pattern of chromosomal changes (losses or gains) in ChRCCs. Conclusions are as follows: (1) ChRCCs showed a significantly broader spectrum of chromosomal aberrations than previously recognized. While previously published chromosomal losses were found in our cohort, gains of multiple chromosomes were also identified in a high percentage. The most frequently detected gains involved chromosomes 4, 7, 15, 19, and 20. (2) There is no relation between chromosomal numerical changes and Paner grading system.

Extensive peritoneal carcinomatosis secondary to renal cell carcinoma with sarcomatoid and rhabdoid differentiation

Renal cell carcinoma (RCC), the most common malignancy of kidney, originates from renal tubular epithelium. It is subclassified based on histological and molecular features. Rarely, RCC can show focal to extensive sarcomatoid or rhabdoid differentiation. RCC with extensive sarcomatoid differentiation and no identifiable epithelial component is designated as unclassified RCC with sarcomatoid differentiation. Presence of sarcomatoid or rhabdoid differentiation is associated with poor prognosis. We describe autopsy findings in a case of RCC with extensive sarcomatoid and focal rhabdoid differentiation presenting with malignant ascites secondary to peritoneal carcinomatosis and multiorgan metastasis.

Synchronous clear cell renal cell carcinoma and tubulocystic carcinoma: genetic evidence of independent ontogenesis and implications of chromosomal imbalances in tumor progression

Seven percent of renal cell carcinoma (RCC) cases are diagnosed as "unclassified" RCC by morphology. Genetic profiling of RCCs helps define renal tumor subtypes, especially in cases where morphologic diagnosis is inconclusive. This report describes a patient with synchronous clear cell RCC (ccRCC) and a tubulocystic renal carcinoma (TCRC) in the same kidney, and discusses the pathologic features and genetic profile of both tumors. A 67 year-old male underwent CT scans for an unrelated medical event. Two incidental renal lesions were found and ultimately removed by radical nephrectomy. The smaller lesion had multiple small cystic spaces lined by hobnail cells with high nuclear grade separated by fibrous stroma. This morphology and the expression of proximal (CD10, AMACR) and distal tubule cell (CK19) markers by immunohistochemistry supported the diagnosis of TCRC. The larger lesion was a typical ccRCC, with Fuhrman's nuclear grade 3 and confined to the kidney. Molecular characterization of both neoplasms using virtual karyotyping was performed to assess relatedness of these tumors. Low grade areas (Fuhrman grade 2) of the ccRCC showed loss of 3p and gains in chromosomes 5 and 7, whereas oncocytic areas displayed additional gain of 2p and loss of 10q; the high grade areas (Fuhrman grade 3) showed several additional imbalances. In contrast, the TCRC demonstrated a distinct profile with gains of chromosomes 8 and 17 and loss of 9. In conclusion, ccRCC and TCRC show distinct genomic copy number profiles and chromosomal imbalances in TCRC might be implicated in the pathogenesis of this tumor. Second, the presence of a ccRCC with varying degrees of differentiation exemplifies the sequence of chromosomal imbalances acquired during tumor progression.

Sarcomatoid renal cell carcinoma: a comprehensive review of the biology and current treatment strategies

Recent advancements in the molecular characterization of renal cell carcinoma altered the classification system and now kidney cancer is divided into several distinct histologic subtypes. Although once a separate histologic category, sarcomatoid renal cell carcinoma is no longer considered a separate tumor type because it can occur with all histologic subtypes. Limited research on tumors with sarcomatoid change has led to minimal progress in the understanding and treatment of these tumors. Because the sarcomatoid variant of renal cell carcinoma can account for approximately one in six cases of advanced kidney cancer, we hope to familiarize clinicians with these tumors by describing the historic background, histologic features, molecular characterization, diagnosis, prognosis, treatment strategies, and active clinical trials of this aggressive type of tumor.

Chromophobe Renal Cell Carcinoma With Heterologous (Liposarcomatous) Differentiation

A 44-year-old woman presented with right flank mass of 6 months duration. A right side renal tumor was diagnosed, and a radical nephrectomy was performed. Histopathological examination showed chromophobe renal cell carcinoma (CRCC) with sarcomatoid transformation. The sarcomatous component contained large pleomorphic lipoblasts. The CRCC was positive for Hale’s colloidal iron stain, whereas the sarcomatous component was negative. Based on histopathological and immunohistochemical findings, a diagnosis of sarcomatoid CRCC with heterologous liposarcomatous differentiation was made. To the authors’ knowledge, this is the second reported case of a sarcomatoid CRCC where the sarcomatous component displayed features of liposarcoma. The case has been reported for its rarity.

Clinical genomics of renal epithelial tumors

Kidney and upper urinary tract cancers account for approximately 54,000 cases every year in the United States, and represent about 3.7% of adult malignancies, with more than 13,000 annual deaths. Classification of renal tumors is typically based on histomorphologic characteristics but, on occasion, morphologic characteristics are not sufficient. Each of the most common histologic subtypes harbors specific recurrent genetic abnormalities, such as deletion of 3p in conventional clear cell carcinoma, trisomy 7 and 17 in papillary renal cell carcinoma, multiple monosomies in chromophobe renal cell carcinoma, and a nearly diploid genome in benign oncocytomas. Knowledge of this information can provide diagnostic support and prognostic refinement in renal epithelial tumors. Identification of the specific subtype of a renal tumor is critical in guiding surveillance for recurrence and the appropriate use of targeted therapies. Cytogenomic arrays are increasingly being used as a clinical tool for genome-wide assessment of copy number and loss of heterozygosity in renal tumors. In addition, the improved understanding of the hereditary causes of renal tumors and their role in sporadic malignancies has led to the development of more effective targeted therapies. This review summarizes the genetic and genomic changes in the most common types of renal epithelial tumors and highlights the clinical implications of these aberrations.

Chromophobe renal cell carcinoma with prominent lymph node metastasis and polysomy of chromosome 21: poorly differentiated form or "presarcomatoid" form?

Lymph node metastasis of chromophobe renal cell carcinoma (RCC) is extremely rare. It has been recently reported that sarcomatoid chromophobe RCC frequently show polysomy of chromosomes 1, 2, 6, 10, and 17. In this article, we report an unusual case of chromophobe RCC. A 42-year-old Japanese woman presented with hematuria and complained of inguinal pain 2 months after the initial symptoms. Radical nephrectomy and renal hilar lymphadenectomy were performed. The tumor was 8 cm in greatest diameter; its cut surface was beige in color. Large metastasis to the renal hilar lymph node was identified. Histological examination of the right renal tumor met the criteria of chromophobe RCC. In addition to histological findings of typical chromophobe RCC, small cell foci, comedo-like necrosis, trabecular growth pattern, and sclerosing stroma were observed. However, no sarcomatoid foci were identified anywhere, despite extensive tumor sampling including lymph node lesions. Immunohistochemically, neoplastic cells were positive for E-cadherin and CD117 (c-kit). Ultrastructurally, tumorous cells contained abundant mitochondria and cytoplasmic microvesicles. Fluorescence in situ hybridization showed monosomy of chromosomes 2 and 10 and polysomy of chromosome 21. Finally, we suggest that this tumor may show the poorly differentiated or presarcomatoid form of chromophobe RCC.

Current pathology keys of renal cell carcinoma

CONTEXT

Renal cell carcinoma (RCC) in adults comprises a heterogeneous group of tumours with variable clinical outcomes that range from indolent to overtly malignant. The application of molecular genetic techniques to the study of renal neoplasms has resulted in an improved classification of these entities and a better understanding of the biologic mechanisms responsible for tumour development and progression. The current 2004 World Health Organisation classification of adult renal epithelial neoplasms has expanded rapidly with new categories recently incorporated.

OBJECTIVE

To review and evaluate the evidence implicating pathologic features and classification of RCC in adults as a tool to approach patients' prognosis and modulate current therapy.

EVIDENCE ACQUISITION

Members of Committee 3: Pathology, under the auspices of the International Consultation on Urological Diseases and the European Association of Urology (ICUD-EAU) International Consultation on Kidney Cancer, performed a systematic review using PubMed. Participating pathologists discussed pathologic categories and diagnostic features of RCC in adults.

EVIDENCE SYNTHESIS

We reviewed and discussed articles and the personal experiences of participating uropathologists.

CONCLUSIONS

The conclusions reached by the ICUD-EAU 2010 International Consultation on Kidney Cancer emphasise the appropriate pathologic diagnosis of RCC in adults as a tool to approach patients' prognosis and modulate current therapy. Further emphasis should be placed on defining risk groups of RCC and diagnostic features of unusual tumours such as familial RCC, translocation RCC, and tubular mucinous and spindle cell carcinoma. A number of recently described entities and morphologic variants of classical categories deserves recognition because they can be important in differential diagnosis and therapy.

Molecular pathology of chromophobe renal cell carcinoma: a review

The recognition of chromophobe renal cell carcinoma (RCC) among other distinct types of renal cell tumors (RCT) based on light-microscopic features, such as cytoplasmic and nuclear characteristics, might pose a dilemma in some cases because of morphological pattern overlapping with renal oncocytoma or conventional RCC. The present article reviews chromophobe RCC with focus on aspects of its molecular pathology, which was shown using ancillary modern microarray-based technology that can distinguish it from its mimics and therefore be helpful for its correct diagnosis. Although the high resolution DNA-microarray analyses excluded with all certainty the occurrence of small specific alterations, the loss of entire chromosomes 2, 10, 13, 17 and 21 occurs exclusively in chromophobe RCC and therefore probes localized at these chromosomes might be used to establish the diagnosis of chromophobe RCC in cases with uncertain histology. The usefulness of proposed candidate genes selected by the global gene expression analyses in the diagnostic pathology is far below expectations. The conflicting staining patterns, together with the poor specificity of used antibodies, leads us to believe that these candidate immunomarkers might not help in the separation of chromophobe RCC, with the exception of CD82, which has recently been suggested to be used for routine histological diagnosis.

Multilocular cystic renal cell carcinoma is a subtype of clear cell renal cell carcinoma

Multilocular cystic renal cell carcinoma is an uncommon low grade renal cell carcinoma with unique morphologic features. Its cytogenetic characteristics have not been fully investigated. Its relationship to typical clear cell renal cell carcinoma is uncertain. We evaluated 19 cases of multilocular cystic renal cell carcinoma diagnosed by strict morphologic criteria using the 2004 WHO classification system. The control group consisted of 19 low grade (Fuhrman grades 1 or 2) clear cell renal cell carcinomas. Chromosome 3p deletion status was determined by dual color interphase fluorescence in situ hybridization analysis. Chromosome 3p deletion was identified in 17 out of 19 (89%) of the clear cell renal cell carcinoma cases and 14 out of 19 (74%) of the multilocular cystic renal cell carcinoma cases, respectively. There was no difference in the status of chromosome 3p deletion between clear cell renal cell carcinoma and multilocular cystic renal cell carcinoma (P=0.40). These results support the concept that multilocular cystic renal cell carcinoma as a subtype of clear cell renal cell carcinoma.

Diagnostic usefulness of fluorescent cytogenetics in differentiating chromophobe renal cell carcinoma from renal oncocytoma: a validation study combining metaphase and interphase analyses

We investigated the usefulness of interphase fluorescence in situ hybridization (FISH) analysis to differentiate between 11 chromophobe renal carcinomas and 12 renal oncocytomas, showing different clinical outcomes, when compared with conventional metaphase cytogenetics by karyotyping. Karyotypically, 3 chromophobe renal cell carcinomas showed losses of chromosomes, 3 were polyploid, 1 was normal, and 4 failed to grow. Of 12 oncocytomas, 5 showed a normal numeric karyotype and 6 additional structural rearrangements. FISH on chromophobe renal cell carcinomas showed a high percentage of cases (10/11 [91%]) with multiple numeric losses among chromosomes 1, 2, 6, 10, and 17; this interphase pattern was observed irrespective of the 3 different metaphase karyotypes. Of 12 oncocytomas, 11 (92%) revealed a normal numeric chromosomal status showing at least 2 chromosomes without aneusomy by interphase FISH. The study demonstrates that indeed FISH performed on formalin-fixed, paraffin-embedded tissue can provide clinically useful information more reliably than karyotyping of most of these tumors.

Sarcomatoid chromophobe renal cell carcinoma with heterologous sarcomatoid elements. A case report and review of the literature

Chromophobe renal cell carcinoma (CRCC) is a distinct subtype of renal cell carcinoma (RCC) that is well known for its relatively good prognosis. Sarcomatoid transformation in this tumor, although rare, has been well documented in the literature and, as in other types of RCC, carries an ominous prognosis for the patient. The finding of heterologous elements in the sarcomatoid component of CRCC is an extraordinary event, which has been reported in only 2 previous cases. Here, we present the third such case, occurring in the left kidney of a previously healthy 63-year-old woman. The nephrectomy specimen showed CRCC with extensive sarcomatoid changes displaying heterologous elements in the form of chondrosarcomatous and osteosarcomatous differentiation. As in other sarcomatoid RCCs, this tumor behaves aggressively, with frequent distant metastases. It is important to recognize the sarcomatoid component in these tumors because of its consequential adverse prognosis for the patient.

Genetic profiles in renal tumors

Renal cell carcinoma in adult comprises a heterogeneous group of tumors with variable clinical outcomes, which ranges from indolent to aggressively malignant. The application of molecular genetics techniques to the study of renal neoplasms has resulted in improved classification of these entities and better understanding of biological mechanisms responsible for tumor development and progression. In the present article we review the molecular genetic profiles of different renal cell tumors and discuss their relevance to the carcinogenesis mechanisms and to the clinical diagnosis of renal cell carcinoma. Understanding of the molecular genetics of renal tumors is beneficial in making accurate diagnoses, assessing prognoses, and selecting appropriate and targeted therapeutic options.

Advances and controversies in grading and staging of renal cell carcinoma

Despite the considerable progress made in our understanding of the pathogenesis, genetics, and pathology of renal cell carcinoma (RCC), difficulties remain relating to the prediction of clinical outcome for individual cases. Although there is evidence to show that high-grade tumors have a poorer prognosis when compared to those of low grade, debate remains regarding the predictive value of grading, especially for those tumors classified into the intermediate grades. Numerous composite morphologic and nuclear grading systems have been proposed for RCC and although that of the Fuhrman classification have achieved widespread usage, the validity of the grading criteria of this classification has been questioned. In addition, there are few studies that have attempted to validate the Fuhrman system for RCCs beyond that of the clear cell subtype. Recent studies have indicated that grading of papillary RCC should be based on nucleolar prominence alone and that the components of the Fuhrman grading classification do not provide prognostic information for chromophobe RCC. Independent of tumor grade, the prognostic importance of tumor stage for RCC is well recognized. The Union Internationale Contre le Cancer/American Joint Committee for Cancer Staging and End Results Reporting TNM staging system is now in its sixth edition (2002) and recent refinements have focused on defining size cut points that will identify apparently localized tumors that will develop recurrence and/or metastases despite attempted curative surgery. In parallel with these studies it has been shown that infiltration of the renal sinus is an important prognostic factor, being observed in almost all tumors >7 cm in diameter. Questions remain as to the appropriate stratification of regional extension of RCC, as defined in the T3 tumor-staging category. Recent modifications to this category have been suggested combining the level of infiltration of the venous outflow tract with the presence or absence of infiltration of the adrenal gland and/or perirenal fat. Similarly, the utility of classifying lymph node involvement by tumor is debated, although it is well recognized that lymph node infiltration is associated with a poor prognosis. Although the current TNM classification does provide useful prognostic information it would appear that further modifications are justified to enhance the predictive value of staging for RCC.

2009 update on the classification of renal epithelial tumors in adults

The classification of kidney tumors in adults expands rapidly with new categories recently incorporated. This will result in the modification of the current 2004 World Health Organization (WHO) classification of the adult renal epithelial neoplasms. Emphasis should be placed in defining risk groups categorized as malignant or benign tumors, including a category of tumors with low malignant potential to accommodate recently recognized categories with extremely good prognosis after surgery. Unusual tumors such as familial renal cell carcinoma (RCC), translocation RCC, renal cell carcinoma after neuroblastoma, tubular mucinous and spindle cell carcinoma, and mixed epithelial and stromal tumors are also presented. A number of recently described entities and morphologic variants of classical categories deserve recognition since they can be important in differential diagnosis. This review emphasizes clinical, pathological and genetic features defining renal epithelial tumors in adults.

Molecular Pathology of the Genitourinary Tract: Molecular Pathology of Kidney and Testes

With the advent of newer molecular technologies, our knowledge of cellular mechanisms with tumors of the kidney and testis has grown exponentially. Molecular technologies have led to better understanding of interplay between the von Hippel-Lindau gene and angiogenic cytokines in renal cancer and isochromosome 12p in testicular neoplasms. The result has been development of antiangiogenic-targeted therapy within recent years that has become the mainstay treatment for metastatic renal cell cancer. In the near future, classification and diagnosis of renal and testicular tumors through morphologic analysis will be supplemented by molecular information correlating to prognosis and targeted therapy. This article outlines tumor molecular pathology of the kidney and testis encompassing current genomic, epigenomic, and proteonomic findings.

Molecular and cytogenetic insights into the pathogenesis, classification, differential diagnosis, and prognosis of renal epithelial neoplasms

Renal cell carcinomas comprise a heterogeneous group of epithelial neoplasms with diverse biologic potential and variable clinical outcomes. The application of molecular and cytogenetic techniques to the study of renal neoplasms has improved our understanding of the molecular mechanisms responsible for tumor initiation and progression. Molecular classification of renal cell carcinomas has also provided new avenues for diagnosis, clinical outcome, and therapy response prediction. In this article, we review the molecular markers for various renal epithelial neoplasms and discuss the mechanisms underlying the development of these neoplasms. We also evaluate the use of molecular and cytogenetic techniques in establishing an accurate diagnosis in difficult cases and their potential usefulness in accurately classifying renal neoplasms, assessing prognosis, and selecting appropriate therapy.

Dedifferentiated chromophobe renal cell carcinoma with massive osteosarcoma-like divergent differentiation: a singular entity in the spectrum of retroperitoneal calcifying tumors

Sarcomatoid change in renal cell carcinoma is the result of the dedifferentiation of the "parent" tumor into a high-grade malignancy characterized by sarcoma-like features and associated with an accelerated clinical course and poorer prognosis. Any of the renal cell carcinoma subtypes can undergo sarcomatoid dedifferentiation, with the chromophobe variant being the most prone. The present report describes the case of a woman affected by a classic chromophobe renal cell carcinoma that developed dedifferentiation accompanied by a very rare osteosarcoma-like divergent differentiation, which constituted about 90% of the entire retroperitoneal mass. In addition to presenting the relevant imaging, histopathological, and immunohistochemical findings, this article briefly discusses the main differential diagnosis of retroperitoneal ossifying/ calcifying masses, which could give rise to diagnostic problems either in small biopsies or at imaging.