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Aims: Papillary renal cell carcinoma (PRCC) histologic subtyping is no longer recommended in the 2022 WHO classification. Currently, WHO/ISUP nucleolar grade is the only accepted prognostic histologic parameter for PRCC. ABCC2, a renal drug transporter, has been shown to significantly predict outcomes in PRCC. In this study we evaluated the prognostic significance of ABCC2 IHC staining patterns in a large, multi-institutional PRCC cohort and assessed the association of these patterns with ABCC2 mRNA expression., Methods and Results: We assessed 254 PRCCs for ABCC2 IHC reactivity patterns that were stratified into negative, cytoplasmic, brush-border <50%, and brush-border ≥50%. RNA in situ hybridization (ISH) was used to determine the transcript level of each group. Survival analysis was performed with SPSS and GraphPad software. RNA-ISH showed that the ABCC2 group with any brush-border staining was associated with a significant increase in the transcript level, when compared to the negative/cytoplasmic group (P = 0.034). Both ABCC2 groups with brush-border <50% (P = 0.024) and brush-border ≥50% (P < 0.001) were also associated with worse disease-free survival (DFS) in univariate analysis. Multivariate analysis showed that only ABCC2 IHC brush-border (<50% and ≥50%) reactivity groups (P = 0.037 and P = 0.003, respectively), and high-stage disease (P < 0.001) had a DFS of prognostic significance. In addition, ABCC2 brush-border showed significantly worse DFS in pT1a (P = 0.014), pT1 (P = 0.013), ≤4 cm tumour (P = 0.041) and high stage (P = 0.014) groups, while a similar analysis with high WHO/ISUP grade in these groups was not significant., Conclusion: ABCC2 IHC brush-border expression in PRCC correlates with significantly higher gene expression and also independently predicts survival outcomes., (© 2023 The Authors. Histopathology published by John Wiley & Sons Ltd.)

Papillary renal cell carcinoma (PRCC) classification has traditionally been divided into two histologic types, type 1 and type 2. A new biological stratification system has recently been proposed based on comprehensive morphologic and genomic analysis. The predominant molecular marker in this 4-tiered stratification is the renal drug transporter ABCC2. In this study, we assessed and validated the value of the biological grouping in a PRCC cohort of 176 patients and provided a comprehensive assessment of clinicopathological variables. Tissue microarrays (TMAs) were constructed from nephrectomy specimens. The TMAs were stained with ABCC2 and GATA3 antibodies, and the PRCC cohort was stratified into four groups PRCC1-PRCC4: PRCC1 25%, PRCC2 37%, PRCC3 36%, and PRCC4 2%. PRCC1 demonstrated lower disease stage (p = 0.041) than PRCC2 and PRCC3. The biological stratification was significant on univariate analysis when analyzing both overall survival (p = 0.039) and disease-free survival (p = 0.011). The biological groups maintained the significance of predicting overall survival after adjusting for WHO/ISUP grade, age, pathological stage, and necrosis (p = 0.049, hazard ratio: 5.008, 95% confidence interval: 1.007 to 24.909). In contrast, WHO/ISUP grade did not maintain its significance on multivariate survival analysis. ABCC2 expression profile also separated cases ≤ 4 cm, based on disease-free survival (p = 0.038). None of the patients in the PRCC1 group died of disease during the follow-up period. The proposed biologic stratification adds molecular markers to the traditional morphologic assessment to better stratify patients' prognosis. ABCC2 expression can also potentially serve as a predictive biomarker owing to its known implication in cancer biology and drug resistance., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Papillary renal cell carcinoma (PRCC) is the most common type of RCC in end-stage kidney disease (ESKD). Papillary adenoma (PA) is a small benign lesion morphologically similar to PRCC and is suggested to be its precursor. PA is also prevalent in ESKD. The evolution of PAs to PRCCs and their relationship to ESKD are poorly understood. A total of 140 PAs, normal kidneys, ESKDs, and PRCCs were analyzed. Previously described markers of renal tubular progenitor cells were analyzed using immunohistochemistry and quantified with digital analysis. Progenitor cells were significantly increased in ESKD (P < 0.0001) and PAs (P = 0.02) in comparison with the normal kidney. Pathway analysis using global miRNA and chromosomal copy number variations revealed a common developmental theme between PA and the PRCCs. Whole exome sequencing showed a KMT2C-specific pathogenic mutation among all PAs and PRCCs. KMT2C is a chromosome 7 epigenetic regulator implicated in development and oncogenesis. Collectively, results show possible connection of PRCCs to PA and the progenitor-like cell population, which are increased in response to renal tubular injury. In addition, each PRCC histologic subtype had its own set of mutational changes, indicating divergence from a common precursor. The study reports previously unknown biological aspects of PRCC development and could influence current surveillance criteria and early detection strategies of PRCC tumors., (Copyright © 2019 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Papillary renal cell carcinoma (PRCC) is the most common nonclear cell RCCs and is known to comprise two histological subtypes. PRCC2 is more aggressive and is molecularly distinct from the other subtypes. Despite this, PRCCs are treated together as one entity, and they show poor response to the current therapies that do not target pathways implicated in their pathogenesis. We have previously detected ABCC2 (an ABC transporter), VEGF, and mTOR pathways to be enriched in PRCC2. In this study, we assess the therapeutic potential of targeting these pathways in PRCC2. Twenty RCC cell lines from the Cancer Cell Encyclopedia were compared to the Cancer Genome Atlas PRCC cohort (290), to identify representative PRCC2 cell lines. Cell lines were further validated in xenograft models. Selected cell lines were treated in vitro and in vivo (mice models) under five different conditions, untreated, anti-VEGF (sunitinib), ABCC2 blocker (MK571), mTOR inhibitor (everolimus) and sunitinib + MK571. Sunitinib +ABCC2 blocker group showed a significant response to therapy compared to the other treatment groups both in vitro (P ≤ 0.0001) and in vivo (P = 0.0132). ABCC2 blockage resulted in higher sunitinib uptake, both in vitro (P = 0.0016) and in vivo (P = 0.0031). Everolimus group demonstrated the second best response in vivo. The double-treatment group showed the highest apoptotic rate and lowest proliferation rate. There is an urgent need for individualized therapies of RCC subtypes that take into account their specific biology. Our results demonstrate that combined targeted therapy with sunitinib and ABCC2 blocker in PRCC2 has therapeutic potential. The results are likewise potentially significant for other ABCC2 high tumors. However, the results are preliminary and clinical trials are needed to confirm these effects in PRCC2 patients., (© 2018 The Authors. Published by FEBS Press and John Wiley & Sons Ltd.)

Background: Two histologic subtypes are recognized for papillary renal cell carcinoma (PRCC). Studies have shown that the subtypes differ in characteristic genetic alterations and clinical behavior. Clinically, the subtypes are managed similarly., Objectives: To analyze the biological differences between the two PRCC histological subtypes, in order to further guide their clinical management., Design, Setting, and Participants: PRCC cohort consisting of 317 patients from the Cancer Genome Atlas database and our institution. Patients were stratified according to histologic criteria as type 1, type 2, or not otherwise specified (NOS). Gene and miRNA expression data for the cohort were examined via unsupervised and supervised clustering., Outcome Measurements and Statistical Analysis: Significant molecular signatures for each subtype were used to unravel the implicated molecular pathways via bioinformatics analysis. Survival was compared between the subtypes. Newly discovered biomarkers were used to further stratify survival of patients in the NOS category., Results and Limitations: Tumor genotyping revealed two distinct PRCC subtypes. The top molecular pathways enriched in PRCC1 were WNT, Hedgehog, and Notch signaling (p=0.001-0.01); highlighting an embryonic developmental theme to the pathogenesis of this subtype. PRCC2 showed enrichment in the mTOR, VEGF (p=7.49E-09) and HIF (p=7.63E-05) signaling pathways. Overall survival and disease-free survival significantly differed between the types. ABCC2 expression was identified as a significant prognostic biomarker for the NOS group in univariate (log rank p<0.0001; hazard ratio [HR] >11.63) and multivariate analysis (p=0.003; HR >2.12). ABCC2 expression and its effect on survival should be further validated at the protein level., Conclusions: The classical PRCC types 1 and 2 have two distinct genotypes. We unraveled pathways that indicate that the two types could potentially respond differently to current therapies. We also identified biomarkers that stratify tumors within the PRCC NOS category into prognostic subgroups. Our findings highlight the need for molecular markers to accurately subtype PRCC and guide clinical management., Patient Summary: The two types of papillary renal cancer are treated similarly. We show that the two types have a different genetic makeup, and hence they should be considered two different tumors. There is a different biology underlying each tumor type that can potentially affect the way they respond to treatment. We uncovered genes that can be tested for to guide therapy in some problematic cases for which it hard to define the tumor type., (Copyright © 2016 European Association of Urology. Published by Elsevier B.V. All rights reserved.)

Papillary renal cell carcinoma (PRCC) has 2 histologic subtypes. Almost half of the cases fail to meet all morphologic criteria for either type, hence are characterized as PRCC not otherwise specified (NOS). There are yet no markers to resolve the PRCC NOS category. Accurate classification can better guide the management of these patients. In our previous PRCC study we identified markers that can distinguish between the subtypes. A PRCC patient cohort of 108 cases was selected for the current study. A panel of potentially distinguishing markers was chosen from our previous genomic analysis, and assessed by immunohistochemistry. The panel exhibited distinct staining patterns between the 2 classic PRCC subtypes; and successfully reclassified the NOS (45%) cases. Moreover, these immunomarkers revealed a third subtype, PRCC3 (35% of the cohort). Molecular testing using miRNA expression and copy number variation analysis confirmed the presence of 3 distinct molecular signatures corresponding to the 3 subtypes. Disease-free survival was significantly enhanced in PRCC1 versus 2 and 3 (P=0.047) on univariate analysis. The subtypes stratification was also significant on multivariate analysis (P=0.025; hazard ratio, 6; 95% confidence interval, 1.25-32.2). We propose a new classification system of PRCC integrating morphologic, immunophenotypical, and molecular analysis. The newly described PRCC3 has overlapping morphology between PRCC1 and PRCC2, hence would be subtyped as NOS in the current classification. Molecularly PRCC3 has a distinct signature and clinically it behaves similar to PRCC2. The new classification stratifies PRCC patients into clinically relevant subgroups and has significant implications on the management of PRCC.

MiT family translocation tumors are a group of neoplasms characterized by translocations involving MiT family transcription factors. The translocation renal cell carcinomas, TFE3 (Xp11.2) and TFEB (t6;11) are known members of this family. Melanotic Xp11 translocation renal cancer is a more recently described entity. To date only 14 cases have been described. It is characterized by a distinct set of features including a nested epithelioid morphology, melanin pigmentation, labeling for markers of melanocytic differentiation, lack of labeling for markers of renal tubular differentiation, predominance in a younger age population and association with aggressive clinical behavior. There are noted similarities between that entity and TFE3 associated PEComas. There are no cases reported of equivalent melanotic TFEB translocation renal cancer. We report 2 rare cases of melanotic translocation renal neoplasms. The first is a melanotic TFE3 translocation renal cancer with an indolent clinical course, occurring in a patient more than 3-decades older than the usual average age in which such tumors have been described. The other case is, to our knowledge, the first reported melanotic TFEB translocation cancer of the kidney. Both cases exhibit the same H&E morphology as previously reported in melanotic translocation renal cancers and label accordingly with HMB45 and Melan-A. While the TFE3 melanotic tumor lacked any evidence of renal tubular differentiation, the TFEB melanotic cancer exhibited some staining for renal tubular markers. Based on the unique features noted above, these two cases expand the clinical and molecular spectrum of the melanotic translocation renal cancers., (Copyright © 2017 Elsevier GmbH. All rights reserved.)