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 has low frequency of alterations in chromosomes 7, 17, and Y

In papillary renal neoplasm with reverse polarity (PRNRP), the status of chromosomal copy number alterations, especially chromosomes 7/17 gain and chromosome Y loss, has remained controversial. In the literatures, there is a discrepancy among the results of chromosomal alteration in PRNRP depending on the analytical methods. Here, we comprehensively analyzed the status of chromosomal abnormalities in PRNRP. Nineteen PRNRP cases were analyzed by fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC), five of which were additionally subjected to array-based comparative genomic hybridization (aCGH) analysis. Fifteen cases of PRCC were used as controls. From the aCGH results, no genome copy number abnormalities were found in the five PRNRP cases. By FISH, numbers of nuclei with abnormal chromosomal signals in PRNRP (centromere 7 gain: 11-21% of nuclei, centromere 17 gain: 11% of nuclei, centromere Y loss: 14-31% of nuclei) were similar to those in non-neoplastic tubular cells (centromere 7 gain: 11-15% of nuclei, centromere 17 gain: 12-15% of nuclei, centromere Y loss: 13-45% of nuclei). c-MET immunohistochemical overexpression, a substitute marker for chromosome 7 trisomy, was observed in 0 of 19 PRNRP cases, consistent with the analyses by aCGH and NGS regarding chromosome 7 gain. Taken together, the frequency of chromosomal alterations in PRNRP is similar to that in non-neoplastic tubular cells, and lower than that in PRCC. Our data suggest that PRNRP has a different tumorigenesis and is a distinct entity from PRCC.

Concordance of MTOR Pathway Mutations and the Diagnosis of Renal Low-Grade Oncocytic Tumor (LOT)

The differential diagnosis for oncocytic renal tumors spans the spectrum from benign entities to more aggressive renal cell carcinomas (RCC). Recent work has characterized a provisional renal oncocytic neoplasm, namely the low-grade oncocytic tumor (LOT), which demonstrates overlapping morphologic features with oncocytoma and chromophobe RCC, but also has a unique immunoprofile (ie, diffusely positive for KRT7, negative for KIT) and a high rate (80% to 100%) of mTOR pathway gene alterations. Given the diagnostic overlap among oncocytic tumors, we looked for concordance between mTOR pathway mutations and LOT. Thirty low-grade renal oncocytic neoplasms underwent histologic review and immunohistochemistry for KRT7 and KIT. Tumors were classified as "determinate" (eg, LOT) for tumors with solid, nested or vaguely tubular growth and diffuse KRT7 staining and negative KIT, or "indeterminate" if the morphology and/or immunostains did not fully support a definitive LOT diagnosis. Next-generation sequencing was performed without any knowledge of the diagnoses, and identified mTOR pathway mutations in 80% (12/15) of the determinate tumors, compared with 7% (1/15) in the indeterminate group. One determinate tumor was reclassified as papillary RCC (MTOR mutation negative) and 6 indeterminate tumors were confirmed to be oncocytoma (N = 4), clear cell RCC or papillary RCC with reverse polarity, respectively. Overall, integration of morphology, immunohistochemistry, and molecular data enabled a final definitive diagnosis for 70% of tumors (21 of the total 30), with a high concordance (93%) for LOT specifically in the determinate group; the remaining 9 tumors (30%) were classified as renal oncocytic neoplasm, not otherwise specified.

Papillary renal neoplasm with reverse polarity: an observational study of histology, immunophenotypes, and molecular variation

Background

Papillary renal neoplasm with reverse polarity (PRNRP) is a novel entity with unique clinicopathological characteristics, and only a small number of patients with PRNRP have been described.

Methods

We retrospectively analyzed the data for nine patients with PRNRP and evaluated differences in the clinical, histomorphological, immunohistochemical, and molecular features; prognosis; and differential diagnosis of PRNRP from other renal tumors with papillary structure.

Results

There were six males and three females aged 36 to 74 years (mean: 62.33 years; median: 68 years). All the tumors were solitary and ranged from 1 to 3.7 cm (mean: 2.17 cm; median: 2 cm), with three and six tumors arose in the left and right renal tract, respectively. Pathologically, PRNRP is a small, well-circumscribed neoplasm with predominant papillary formations. The lining epithelium is composed of a monolayer of cuboidal to low-columnar cells with low-grade nuclei arranged against the apical pole of the tumor cells. Edema, mucinous degeneration, and hyaline degeneration are found in the fibrovascular cores. Foamy macrophages, psammoma bodies, hemosiderin deposition, and infiltrative tumor boundaries were present in some patients. Immunohistochemically, all tumors showed diffuse positive staining for GATA3. Sanger sequencing confirmed the presence of KRAS mutation in seven patients. All patients had a good prognosis after surgery and were relapse free. Positive staining for GATA3 and negative staining for vimentin were the most significant markers for differentiating PRNRP from other renal tumors with analogous structure.

Conclusions

These findings suggested that PRNRP is a distinctive subtype of renal tumor with specific pathological features and indolent behaviors that should be distinguished from other renal tumors, especially papillary renal cell carcinoma. A monolayer of tumor cells with an inverted nuclear pattern, positive staining for GATA3, and KRAS mutation are essential for pathological diagnosis. Owing to its satisfactory prognosis, the surveillance and follow-up of patients with PRNRP should be additionally formulated.

Clinicopathological, Immunohistochemical, and Molecular Characteristics of Pigmented Microcystic Chromophobe Renal Cell Carcinoma with Favorable Prognosis

Background. Pigmented microcystic chromophobe renal cell carcinoma (RCC) is a subtype of chromophobe RCC. Its distinct histopathologic features are microcystic and microtubular pattern, pigmentation, and microcalcifications. Pigmented microcystic chromophobe RCC has ultrastructure, immunophenotypic structure, and molecular results similar to chromophobe RCC. Methods. We report five tumors of pigmented microcystic chromophobe RCC. Morphological observation and immunohistochemical examination were performed, and clinical and molecular features were analyzed. Results. Microscopically, all five tumors showed brown pigmentation, microcystic, and tubular cystic structures, one tumor presented microscopic calcifications. All tumors were positive for EMA, AE1/AE3, PAX8, KRT7, KIT (CD117), claudin 7, KRT8, and E-cadherin, and three tumors expressed P504S. All tumors were negative for vimentin, CA9, KRT20, TFE3, TFEB, Melan-A, HMB45, FH, SDHB, and GATA3. Ki-67 index varied from less than 1% to 2%. In three tumors, next-generation sequencing of the 688 gene was performed, the results found gene variants with potential clinical significance such as JMJD1C, MYCL, TP53, PI3KCA, KRAS, APC, GLI1, LRRK2, and gene variants with unclear clinical significance such as NTRK1 and RAD50; All patients remained alive over a follow-up period of 8-46 months without tumor recurrence and sarcomatoid transformation. Conclusions. Pigmented microcystic chromophobe RCC has a relatively benign biological behavior, and distant metastases and sarcomatoid transformation are rare. This overview of five additional tumors of pigmented microcystic chromophobe RCC offers further insight into this special subtype of chromophobe RCC.

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.

Papillary Renal Cell Carcinoma: A Review of Prospective Clinical Trials

OPINION STATEMENT

PRCC is a unique histologic entity compared to other forms of renal cell carcinoma, harboring distinct molecular drivers. The WHO 2022 classification is further emphasizing the molecular biology by making molecular classifications of PRCC subclassifications and discontinuing the morphologic type 1 and type 2 classification system. We agree with this functional classification system and encourage all future clinical trials to only include patients with similar diagnosis instead of conducting basket trials (including all nccRCC together) which limits the scientific value of those conclusions. Based on recent disease-specific clinical trial (S1500, PAPMET), the current standard of care for patients with treatment naïve PRCC is cabozantinib. Prospective clinical trials clearly establish that immune checkpoint inhibitor therapy has meaningful activity in PRCC. The data to date include only single-arm clinical trials of combination immune therapy. Despite the positive and encouraging results, we need validation through randomized studies because of the overestimation of effect size seen in single-arm trials. These randomized trials are currently underway and enrolling. We strongly encourage all physicians to support these studies and enroll patients with PRCC to these trials in order to continue improving the standard of care.