Papillary Renal Neoplasm With Reverse Polarity Is Often Cystic: Report of 7 Cases and Review of 93 Cases in the Literature

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.

Papillary Renal Cell Carcinoma: Evolving Classification by Combined Morphologic and Molecular Means

Papillary renal cell carcinoma classification has evolved as a result of attentive morphologic observations by pathologists coupled with specific immunohistochemical, molecular, and clinical data. Refinement of this relatively common diagnostic category of renal neoplasia has resulted in the parsing out of specific renal cell carcinoma subtypes that no longer belong in the papillary renal cell carcinoma category and can have distinct familial and prognostic implications (eg, fumarate hydratase (FH)-deficient renal cell carcinomas). In addition, evolving classification has enabled more accurate diagnosis by surgical pathologists (through the description of recognizable morphologic variants). In many cases, molecular findings have aided and confirmed morphologic categorization. The combination of morphologic and molecular findings continues to provide important prognostic information for patients and their clinicians.

[Papillary renal neoplasm with reverse polarity]

Papillary renal neoplasm with reverse polarity is a rare subtype of papillary renal cell tumors with unique morphology, specific molecular features and good prognosis. The article presents literature data and describes our own observation of a papillary kidney tumor with reverse nuclear polarity in a 73-year-old patient. The difficulties of preoperative diagnosis of a tumor are shown, histological and immunohistochemical criteria for diagnosis and differential diagnosis of this tumor with other kidney tumors are presented. This rare case is of interest for both pathologists and clinicians.

Papillary renal neoplasm with reverse polarity: a clinicopathologic study of 43 cases with a focus on the expression of KRAS signaling pathway downstream effectors

Papillary renal neoplasm with reverse polarity (PRNRP) is a renal tumor with frequent KRAS mutations. In this study, we aimed to report the clinical, histological, and immunohistochemical characteristics of PRNRP and the protein expression of various KRAS signaling pathway downstream effectors in PRNRP. PRNRP samples from patients who underwent surgical resection at Seoul National University Hospital over an 11-year period (January 2011 to December 2021) were analyzed. We identified 43 PRNRPs, defined as papillary renal tumors with a thin papillary architecture, eosinophilic finely granular cytoplasm, and apical nuclear position. Immunohistochemistry revealed typical characteristics of PRNRP, including exclusively positive GATA3 (43/43); highly positive L1CAM (43/43), PAX8 (43/43), and EMA (43/43); and low positive AMACR (4/43), RCC (1/43), and vimentin (1/43). KRAS signaling pathway effectors, such as p-ERK, RalA, and RalB, were highly expressed in PRNRP compared to papillary renal cell carcinoma (pRCC) with low or high nuclear grade (P < .001, all). Compared to pRCC with high nuclear grade, patients with PRNRP exhibited significantly longer progression-free survival (P < .001). PRNRP showed the best clinical outcome, with no disease progression in any of the cases. Our study analyzed the largest number of PRNRP cases and is the first to analyze the association between PRNRP and the KRAS downstream signaling pathway. PRNRP was found at a high frequency among all papillary renal tumors (43/207) and demonstrated a very good prognosis. PRNRP showed high GATA3, L1CAM, PAX8, and EMA protein expression as well as high p-ERK, RalA, and RalB protein expression.

Cytomorphology of papillary renal neoplasm with reverse polarity

Papillary renal neoplasm with reverse nuclear polarity (PRNRP) is an emerging oncocytic renal tumor. Cytomorphologic features of this tumor have not been described in the literature before. The objective of this study was to review the cytomorphology of a case PRNRP and compare with cytomorphologic features of papillary renal cell carcinomas (pRCCs) reported in the literature. 1 case of core needle biopsy (CNB) with touch preparation (TP) of a renal mass diagnosed as PRNRP was reviewed retrospectively. Clinical presentation, cytomorphologic features, ancillary tests and histopathology results were analyzed. The touch preparation was cellular and showed tight 3-D clusters of cuboidal epithelial cells with variable presence of fibrovascular cores (FC), granular eosinophilic cytoplasm, round apically located grade 1 nuclei compared to cases of pRCC that consistently showed presence of FCs lined by cuboidal to columnar epithelial cells with variable degree of cytologic atypia. Features characteristic of pRCC like foamy macrophages, hemosiderin laden macrophages, nuclear grooves or psammoma bodies were not present. No necrosis or mitosis were identified. By immunohistochemistry (IHC) the tumor cells were positive for cytokeratin 7, GATA-3 and AMACR (focal) and negative for CA-IX, CD117 and vimentin. Cytomorphologic features of PRNRP are unique and characterized by tight 3-D clusters (with or without FCs) of cuboidal cells with small round apically located nuclei and finely granular oncocytic cytoplasm. Specific diagnosis of PRNRP on cytology or CNB is feasible along with use of ancillary tests IHC and /or molecular tests.

Ipsilateral synchronous papillary renal neoplasm with reverse polarity and urothelial carcinoma in a renal transplant recipient: a rare case report with molecular analysis and literature review

BACKGROUND

Renal transplant recipients (RTRs) have a 3- to 5-fold higher risk of developing malignant tumors than the general population, with new malignant tumors after transplantation considered to be the leading cause of death in RTRs. In pathological practice, it is rare for neoplasms with different histology to be located in the same organ. We report the first case of a synchronous papillary renal neoplasm with reverse polarity (PRNRP) and urothelial carcinoma (UC) in the ipsilateral kidney in an RTR. Molecular detection was conducted by next-generation sequencing.

CASE PRESENTATION

A 68-year-old female suffered from uremia 19 years ago and underwent renal transplantation (RT) after receiving dialysis for 6 months. Hematuria occurred one month ago and an enhanced CT showed that there were two abnormal density foci in the middle and lower parts of the autologous left kidney. A laparoscopic left nephrectomy and ureterectomy were performed. Gross examination revealed a mass (I) in the left renal parenchyma, 2*1.8*1.5 cm in size, that protruded from the renal capsule, and a cauliflower-like mass (II), 5*2.5*2 cm in size, adjacent to the mass (I). Microscopic findings revealed these lesions were PRNRP and UC, respectively. PCR analysis revealed a KRAS gene mutation (G12D in exon 2) in the PRNRP, while NGS analysis revealed FGFR3 (S249C in exon 7) and KDM6A (Q271Ter in exon 10 and A782Lfs in exon 17) mutations in the UC.

CONCLUSIONS

We report here for the first time an extraordinarily rare case of synchronous renal tumors of a PRNRP and UC in the ipsilateral kidney of an RTR. We identified simultaneous KRAS, FGFR3, and KDM6A mutations in two different renal masses in the ipsilateral kidney. Pathologic assessment with comparative molecular analysis of mutational profiles facilitates tumor studies after RT and may be of great value in clinical management strategies.

Rare papillary renal neoplasm with reverse polarity: A case report and review of the literature

Papillary renal neoplasm with reverse polarity (PRNRP) is a rare renal tumour and was newly named in 2019. This study reported a case of a 30-year-old female patient with a left renal tumour without any clinical symptoms and whose CT scan of her left kidney showed a mass of 2.6 cm×2.3 cm, which was considered to be renal clear cell carcinoma. Laparoscopic partial nephrectomy was performed, and histopathology and immunohistochemistry confirmed papillary renal neoplasm with reverse polarity, which had unique clinicopathological features, immunophenotype, KRAS gene mutation and relatively indolent biological behaviour. As newly diagnosed cases, rigorous and regular follow-up is necessary. In addition, a literature review was performed from 1978 to 2022, and 97 cases of papillary renal neoplasms with reverse polarity were identified and analysed.

Cell block-based RNA next generation sequencing for detection of gene fusions in lung adenocarcinoma: An institutional experience

OBJECTIVE

Targeted therapy is an important part of the treatment of lung adenocarcinoma. Tests for EGFR mutation, ALK, ROS1, RET and NTRK gene fusions are needed to make a treatment decision. These gene fusions are traditionally detected by fluorescence in situ hybridisation (FISH) or immunohistochemistry. In this study, we investigated whether gene fusions in pulmonary adenocarcinoma could be accurately detected by RNA next-generation sequencing (RNA-NGS) and whether cytology cell blocks could be used effectively for this test.

METHODS

Archived cytological specimens of lung adenocarcinoma submitted for RNA sequencing between 2019 and 2022 at Fox Chase Cancer Center were retrospectively retrieved. Hybrid capture-based targeted RNA next generation sequencing was used, which covers 507 fusion genes, including ALK, ROS1, RET and NTRKs, irrespective of their partner genes. DNA NGS, FISH and chromosomal microarray analysis were used to confirm the results of the RNA-NGS.

RESULTS

A total of 129 lung adenocarcinoma cytology specimens were submitted for molecular testing. Eight of 129 (6.2%) cases were excluded from RNA sequencing as their cell blocks contained inadequate numbers of tumour cells. One case (0.8%) failed to yield adequate RNA. The overall success rate was 93% (120/129). Ten of 120 (8.3%) cytology cases were positive for gene fusions, including 7 ALK, 2 ROS1 fusion genes, and 1 RET fusion gene. Twenty-two cell block cases were also tested for ALK fusion genes using FISH. However, 11 of 22 (50%) failed the testing due to inadequate material.

CONCLUSIONS

Cytology cell blocks can be used as the main source of material for molecular testing for lung cancer. Detection of gene fusions by RNA-based NGS on cell blocks is convenient and reliable in daily practice.

Papillary renal cell neoplasm with reverse polarity: A new subtype of renal tumour with favorable prognosis

INTRODUCTION

Papillary renal cell neoplasm with reverse polarity (PRNRP) has recently been recognized as an entity separate from the traditional classification of papillary renal cell carcinomas, due to its specific histopathological, immunophenotypic and molecular characteristics, as well as its indolent behavior.

MATERIAL AND METHODS

We provide 6 new cases and a review of the literature published until the present time, which comprises a total number of 104 cases.

RESULTS

Our PRNRP cases correspond to 5 men and one woman aged between 47 and 91 years. In 5 of the 6 cases, the PRNRP was an incidental finding in nephrectomy specimens. Nephrectomy had been indicated due to the presence of another renal tumor, except for one case, in which surgical intervention was indicated due to PRNRP. Our cases present mass sizes between 2 and 13 mm, as well as papillary histology with a monolayered lining of eosinophilic cells with low-grade nuclei in apical location. Immunohistochemically, they show a constant positivity for GATA3 and negativity for vimentin. KRAS mutations were identified in 50% of our cases. After a follow-up ranging between one and 60 months, 5 of the cases were still alive without recurrences or metastases, and one died from urothelial carcinoma.

CONCLUSIONS

Our cases agree with the clinical and pathological characteristics described in the PRNRP cases published to date. With the present study, we provide the first series of national cases corroborating the existence of well-defined and constant diagnostic criteria that allow PRNRP to be considered as a distinctive entity.

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.

Papillary renal neoplasm with reverse polarity-a comparative study with CCPRCC, OPRCC, and PRCC1

Papillary renal neoplasm with reverse polarity (PRNRP) is a newly defined entity with distinct histomorphology and recurrent KRAS mutation. In this study, we aimed to identify and analyze the clinicopathological, immunohistochemical (IHC), and molecular features of PRNRP in our center and to evaluate its differential diagnosis with other tumors with which it is easily confused: clear cell papillary renal cell carcinoma (CCPRCC), oncocytic papillary renal cell carcinoma (OPRCC), and papillary renal cell carcinoma type 1 (PRCC1). Nephrectomy specimens of PRNRP (n = 15), CCPRCC (n = 11), and OPRCC (n = 12) were retrieved from our pathology archives. We also selected typical cases of PRCC1 (n = 15) as a control group. PRNRP accounted for 3.05% (15/492) of all PRCC cases at our center. The median follow-up period was 41.3 months. All PRNRP cases were pT1N0M0, and only one involved recurrence (1 year after surgery). IHC analysis showed diffuse staining of CK7, EMA, and GATA3 but weak or negative staining of CD10, CD117, p504s, and vimentin in the PRNRP samples and distinctive IHC features in the other three tumor types. KRAS mutation was detected in 4/10 PRNRP cases. Among the 40 most commonly mutated genes identified, 5 (BCLAF1, PDE4DIP, NCOR1, PARP4, and PABPC1) have actionable alterations. Our study supports the suggestion that PRNRP is an entity distinct from CCPRCC, OPRCC, and PRCC1.

Papillary renal neoplasm with reverse polarity with a favorable prognosis: Two cases report and literature review

Background

Papillary Renal Neoplasm (PRN) with polarity inversion is a less common subtype of kidney cancer with an apparently recognizable morphology, distinct immunohistochemical profiles, and frequent KRAS mutations. It has been estimated to account 4% of previously diagnosed PRN.

Case presentation

This is a retrospective case report of two patients diagnosed with PRNRP. Two males were found to have kidney mass accidentally through imaging examination in clinic. Both of the patients had no obvious discomfort and abnormal test indicators. Subsequently, they underwent partial nephrectomy in our center by the same surgeon and followed up closely with an impressive clinical outcome. The pathology reports indicated that their pathological features were consistent with PRNRP. The HE staining showed a monolayer of papillary or tubular structures, with small nuclei away from the cytoplasmic top of the basement membrane. The immunohistochemical results were GATA3 (+), vimentin (-).

Conclusion

Our case reports and literature review suggested that PRNRP should be separated from traditional PRN and partial nephrectomy is a robust modality for PRNRP. The morphological, immunohistochemical, and genetic information of the cases we presented would provide important material for PRNRP to become a distinct category with benign clinical outcome.

WHO 2022 landscape of papillary and chromophobe renal cell carcinoma

The 5th edition of the WHO Classification of Tumours of the Urinary and Male Genital Systems contains relevant revisions and introduces a group of molecularly defined renal tumour subtypes. Herein we present the World Health Organization (WHO) 2022 perspectives on papillary and chromophobe renal cell carcinoma with emphasis on their evolving classification, differential diagnosis, and emerging entities. The WHO 2022 classification eliminated the type 1/2 papillary renal cell carcinoma (pRCC) subcategorization, given the recognition of frequent mixed tumour phenotypes and the existence of entities with a different molecular background within the type 2 pRCC category. Additionally, emerging entities such as biphasic squamoid alveolar RCC, biphasic hyalinising psammomatous RCC, papillary renal neoplasm with reverse polarity, and Warthin-like pRCC are included as part of the pRCC spectrum, while additional morphological and molecular data are being gathered. In addition to oncocytomas and chromophobe renal cell carcinoma (chRCC), a category of 'other oncocytic tumours' with oncocytoma/chRCC-like features has been introduced, including emerging entities, most with TSC/mTOR pathway alterations (eosinophilic vacuolated tumour and so-called 'low-grade' oncocytic tumour), deserving additional research. Eosinophilic solid and cystic RCC was accepted as a new and independent tumour entity. Finally, a highly reproducible and clinically relevant universal grading system for chRCC is still missing and is another niche of ongoing investigation. This review discusses these developments and highlights emerging morphological and molecular data relevant for the classification of renal cell carcinoma.

Recurrent KRAS mutations are early events in the development of papillary renal neoplasm with reverse polarity

We evaluated the clinicopathologic and molecular characteristics of mostly incidentally detected, small, papillary renal neoplasms with reverse polarity (PRNRP). The cohort comprised 50 PRNRP from 46 patients, divided into 2 groups. The clinically undetected (<5 mm) neoplasms (n = 34; 68%) had a median size of 1.1 mm (range 0.2-4.3 mm; mean 1.4 mm), and the clinically detected (≥5 mm) neoplasms (n = 16; 32%) which had a median size of 13 mm (range 9-30 mm; mean 16 mm). Neoplasms were positive for GATA3 (n = 47; 100%) and L1CAM (n = 34/38; 89%) and were negative for vimentin (n = 0/44; 0%) and, to a lesser extent, AMACR [(n = 12/46; 26%; weak = 9, weak/moderate = 3)]. KRAS mutations were found in 44% (n = 15/34) of the clinically undetected PRNRP and 88% of the clinically detected PRNRP (n = 14/16). The two clinically detected PRNRP with wild-type KRAS gene were markedly cystic and contained microscopic intracystic tumors. In the clinically undetected PRNRP, the detected KRAS mutations rate was higher in those measuring ≥1 mm vs <1 mm [n = 14/19 (74%) vs n = 1/15 (7%)]. Overall, the KRAS mutations were present in exon 2-codon 12: c.35 G > T (n = 21), c.34 G > T (n = 3), c.35 G > A (n = 2), c.34 G > C (n = 2) resulting in p.Gly12Val, p. Gly12Asp, p.Gly12Cys and p.Gly12Arg, respectively. One PRNRP had a G12A/V/D complex mutation. Twenty-six PRNRP were concurrently present with other tumors of different histologic subtypes in the ipsilateral kidney; molecular testing of 8 of the latter showed wild-type KRAS gene despite the presence of KRAS mutations in 5 concurrent PRNRP. On follow up, no adverse pathologic events were seen (range 1-160 months; mean 44 months). In conclusion, the presence of KRAS mutations in small, clinically undetected PRNRP provides a unique finding to this entity and supports its being an early event in the development of these neoplasms.

Papillary renal neoplasm with reverse polarity: A clinicopathological and molecular genetic characterization of 16 cases with expanding the morphologic spectrum and further support for a novel entity

Papillary renal neoplasm with reverse polarity (PRNRP) is a recently described, rare renal tumor that differs clinically, morphologically, and molecularly from papillary renal cell carcinoma (RCC). To further characterize the pathological spectrum of this rare tumor, in this study, we retrospectively identified 16 cases of PRNRP from three institutions to comprehensively investigate the clinicopathological and molecular genetic features, using immunohistochemistry (IHC), fluorescence in-situ hybridization (FISH), and targeted next-generation sequencing (NGS). The patients included nine men and seven women, with age ranging from 47 to 80 years (median = 67.5 years, mean = 65 years). The tumor size ranged from 0.4 to 9.5 cm in the greatest dimension (median = 1.8 cm, mean = 2.6 cm). Most tumors (12/16) were incidentally identified by imaging studies. By AJCC stage, 15 were categorized as pT1 and 1 was pT2. Follow-up showed no recurrences, metastases, or disease-related deaths in all the 16 patients. Grossly, 14 cases demonstrated at least a partially cystic appearance. Microscopically, all PRNRPs except 1 (case 13) were composed predominantly of thin, branching papillary architecture covered by a single layer of cuboidal cells with finely granular cytoplasm, and low-grade nuclei typically located toward the apical surface away from the basement. Case 13 consisted mostly of solid, densely packed tubules with only a minor papillary component (5%). Other commonly seen histological features included hyalinized or edematous papillae (n = 11), lymphocyte aggregation in fibrovascular cores (n = 10), mast cell infiltration (n = 8), and intralesional hemorrhage (n = 7). Uncommonly seen histological features included lymphoid cuff (n = 4), hemosiderin deposition (n = 5), foci of clear cell change (n = 4), intracytoplasmic vacuoles (n = 4), eosinophilic hobnail cells (n = 2), and infarct-type necrosis (n = 1). Two PRNRPs were concurrent with ipsilateral clear cell papillary RCC and clear cell RCC, respectively. By IHC, the tumors were consistently positive for GATA3, CK7, and PAX8. Fourteen out of 16 tumors showed a basolateral-membranous E-cadherin expression pattern, and 12/16 cases were positive for 34βE12.The expression of AMACR, CD10, and vimentin was either absent or only weak and focal. By targeted NGS, 13/14 evaluated PRNRPs harbored KRAS missense mutations involving c.35G>T resulting in p.G12V (7/13), c.35G>A resulting in p.G12D (4/13), and c.34G>T resulting in p.G12C (2/13). By FISH, 1/15 had gains of chromosomes 7 and 17, and 2/8 male cases had deletion of chromosomes Y. In conclusion, our study confirms that PRNRP is an indolent renal cell neoplasm with unique morphology, consistent immunohistochemical profile, and recurrent KRAS mutation. Our study expands the morphologic spectrum of PRNRP and provides further evidence supporting it as a novel entity.

Papillary renal cell carcinoma: current and controversial issues

PURPOSE OF THE REVIEW

Papillary renal cell carcinoma (pRCC) is the second most frequent renal cancer subtype and represents 15-20% of all RCC. Classification of pRCC is changing because novel tumour entities have been discovered in the last years. In this review, we summarise recent studies relevant for the understanding of the molecular complexity and the broader differential diagnosis of pRCC.

RECENT FINDINGS

It has been 25 years ago, that pRCC was morphologically subdivided into type 1 and type 2. Recently described tumour entities in the 2022 WHO classification challenged this concept and allow a new view on the molecular background in pRCC. Biphasic hyalinizing psammomatous RCC and papillary renal neoplasm with reversed polarity are emerging tumour entities derived from the new concept of molecularly defined RCC subtypes. Immune checkpoint inhibition and tyrosine kinase inhibitors have been introduced as the new backbone in the first-line treatment of advanced pRCCs. To identify novel targeted treatments for patients with pRCC it is crucial to investigate the specific molecular background of pRCC considering emerging pRCC subtypes.

SUMMARY

In the future, a deeper understanding of the correlation between molecular aberrations and new pRCC subtypes may improve the classification of pRCC patients and could reveal potential predictive biomarkers for each subgroup.

Papillary renal neoplasm with reverse polarity with a favorable prognosis should be separated from papillary renal cell carcinoma

Papillary renal neoplasm with reverse polarity (PRNRP) is a newly documented renal entity with an easily recognizable morphology, distinct immunohistochemical profiles, and frequent KRAS mutations. The latest practice guidelines regard PRNRP as a subtype of papillary renal cell carcinoma due to the documented chromosomal alterations of 7, 17, and Y. This study included 20 patients with PRNRP and 30 patients with PRCC. Statistically significant differences were observed in size, WHO/ISUP grade, macrophages in the papillae, reverse polarity, CK7, basolateral positivity for Claudin7, GATA3 expression, KRAS mutation, and chromosomal alterations. No adverse events such as perinephric invasion, lymphovascular invasion, sarcomatoid of rhabdoid differentiation, metastasis, or recurrence were found in PRNRP. However, PRCC can cause these adverse events. Basolateral positivity for Claudin7 together with GATA3 expression indicated distal tubule derivation of PRNRP. KRAS mutations were detected in 89% (16/18) of PRNRP. No KRAS mutations were detected in PRCC. Six patients with PRNRP had one chromosomal alteration and the other 12 had no chromosomal alterations. However, only four patients with PRCC showed no chromosomal alterations. Eighteen patients had two or three chromosomal alterations. PRCC can metastasize, recur, and even cause death, whereas PRNRP has a favorable prognosis. We recommend that PRNRP should be separated from PRCC and partial nephrectomy is more suitable for PRNRP.