Detection of chromosome copy number alterations in metanephric adenomas by array comparative genomic hybridization

Key Renal Neoplasms With a Female Predominance

Renal neoplasms largely favor male patients; however, there is a growing list of tumors that are more frequently diagnosed in females. These tumors include metanephric adenoma, mixed epithelial and stromal tumor, juxtaglomerular cell tumor, mucinous tubular and spindle cell carcinoma, Xp11.2 (TFE3) translocation-associated renal cell carcinoma, and tuberous sclerosis complex (somatic or germline) associated renal neoplasms. The latter category is a heterogenous group with entities still being delineated. Eosinophilic solid and cystic renal cell carcinoma is the best-described entity, whereas, eosinophilic vacuolated tumor is a proposed entity, and the remaining tumors are currently grouped together under the umbrella of tuberous sclerosis complex/mammalian target of rapamycin-related renal neoplasms. The entities described in this review are often diagnostic considerations when evaluating renal mass tissue on biopsy or resection. For example, Xp11.2 translocation renal cell carcinoma is in the differential when a tumor has clear cell cytology and papillary architecture and occurs in a young or middle-aged patient. In contrast, tuberous sclerosis complex-related neoplasms often enter the differential for tumors with eosinophilic cytology. This review provides an overview of the clinical, gross, microscopic, immunohistochemical, genetic, and molecular alterations in key renal neoplasms occurring more commonly in females; differential diagnoses are also discussed regardless of sex predilection.

KANK1-NTRK3 fusions define a subset of BRAF mutation negative renal metanephric adenomas

Background

Metanephric adenoma (MA) is a rare benign renal neoplasm. On occasion, MA can be difficult to differentiate from renal malignancies such as papillary renal cell carcinoma in adults and Wilms̕ tumor in children. Despite recent advancements in tumor genomics, there is limited data available regarding the genetic alterations characteristic of MA. The purpose of this study is to determine the frequency of metanephric adenoma cases exhibiting cytogenetic aberration t (9;15)(p24;q24), and to investigate the association between t (9,15) and BRAF mutation in metanephric adenoma.

Methods

This study was conducted on 28 archival formalin fixed paraffin-embedded (FFPE) specimens from patients with pathologically confirmed MA. Tissue blocks were selected for BRAF sequencing and fluorescent in situ hybridization (FISH) analysis for chromosomal rearrangement between KANK1 on chromosome 9 (9p24.3) and NTRK3 on chromosome 15 (15q25.3), which was previously characterized and described in two MA cases.

Results

BRAF^V600E mutation was identified in 62% of our cases, 9 (38%) cases were BRAF^WT, and 4 cases were uninformative. Of the 20 tumors with FISH results, two (10%) were positive for KANK1-NTRK3 fusion. Both cases were BRAF^WT suggesting mutual exclusivity of BRAF^V600E and KANK1-NTRK3 fusion, the first such observation in the literature.

Conclusions

Our data shows that BRAF mutation in MA may not be as frequent as suggested in the literature and KANK-NTRK3 fusions may account for a subset of BRAF^WT cases in younger patients. FISH analysis for KANK1-NTRK3 fusion or conventional cytogenetic analysis may be warranted to establish the diagnosis of MA in morphologically and immunohistochemically ambiguous MA cases lacking BRAF mutations.

Pediatric Renal Tumors: Updates in the Molecular Era

Molecular characterization has led to advances in the understanding of pediatric renal tumors, including the association of pediatric cystic nephromas with DICER1 tumor syndrome, the metanephric family of tumors with somatic BRAF mutations, the characterization of ETV6-NTRK3-negative congenital mesoblastic nephromas, the expanded spectrum of gene fusions in translocation renal cell carcinoma, the relationship of clear cell sarcoma of the kidney with other BCOR-altered tumors, and the pathways affected by SMARCB1 alterations in rhabdoid tumors of the kidney. These advances have implications for diagnosis, classification, and treatment of pediatric renal tumors.

Molecular characterisation of metanephric adenomas beyond BRAF: genetic evidence for potential malignant evolution

AIMS

Metanephric adenomas (MAs) are conventionally regarded as rare renal tumours with indolent behaviour; limited case reports have described MAs with aggressive features. Conventional MAs harbour hotspot BRAF V600E mutations. A BRAF V600E senescence pathway, mediated by cyclin-dependent kinase inhibitor 2A (CDKN2A)/p16, has been proposed to confer MA benignity. Aside from BRAF, the molecular landscape in both conventional MAs and those with aggressive features has not been fully characterised. The aim of this study was to molecularly profile a series of MAs to investigate the correlation between genomic findings and clinical outcome.

METHODS AND RESULTS

We retrospectively examined the histomorphology and patient outcomes of 11 conventional MAs and one MA with aggressive features. Each was subjected to capture-based next-generation DNA sequencing of 479 cancer-related genes and immunohistochemical profiling. All tumours were positive for WT1 immunostaining and BRAF V600E mutation. One conventional MA contained an additional somatic BRCA2 pathogenic mutation. The MA with aggressive features had a biphasic appearance: one component was epithelial, with areas morphologically consistent with conventional MA; the second component was sarcomatous, with areas of solid and angiosarcomatous growth. Differential profiling of the two populations revealed identical BRAF, EIF1AX and TERT promoter hotspot mutations in the epithelial and sarcomatous components. Deep deletion of CDKN2A and MYC amplification were identified only in the sarcomatous component.

CONCLUSIONS

Although the vast majority of MAs show indolent behaviour, rare pathogenic alterations can occur in conventional MAs in addition to BRAF. Molecular profiling of a case with aggressive clinical and pathological features shows genetic evidence for malignant evolution in MAs.

Cytologic features of metanephric adenoma of the kidney: case report and review of the literature

Metanephric adenoma (MA) is a rare, benign renal tumor that can be found in individuals of any age. The histological features of this lesion are well known; however, cytological features of this entity have rarely been described. Herein, we present the case of a 37-year-old white woman with multiple endocrine dysfunctions and a renal mass. The diagnosis of metanephric adenoma was suggested as a differential diagnosis during imprint cytology; this diagnosis was later confirmed by core needle biopsy (CNB) and the results of immunostaining. To our knowledge, this is the first time in the literature that the diagnosis of metanephric adenoma was initially suggested on imprint cytologic testing of a CNB. We review the literature regarding the cytologic features and immunohistochemical reactivity of this tumor to raise awareness of this entity among pathologists and to distinguish it from other lesions, such as renal-cell carcinoma, so physicians can use this information to help them avoid calling for an unnecessary radical nephrectomy.

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.

CT imaging spectrum and the histopathological features of adult metanephric adenoma

OBJECTIVE

To retrospectively evaluate the radiopathological features of adult metanephric adenoma (MA) and explore whether MA can be differentiated on CT images, including the basis of their morphological features and enhancement patterns.

METHODS

18 consecutive MA cases (age range, 18-66 years; 9 males and 9 females) were pathologically proven and recruited in our study between January 2004 and June 2014. Unenhanced and contrast-enhanced CT were performed and correlated with corresponding pathological findings to differentiate between MA and other renal tumours. The enhancement pattern, lesion contour and presence of calcifications were evaluated.

RESULTS

On unenhanced CT scan, the most common (n = 15, 83.3%) CT imaging characteristics were the presence of homogeneity and well-defined solid renal masses; the minority (n = 3, 16.7%) were heterogeneous or centrally located low-attenuation masses. Contrast-enhanced CT image revealed hypoattenuating heterogeneous masses with varying degrees of contrast enhancement in 16 (88.9%) cases, in contrast to those without increased attenuation in 2 (11.1%) cases. Scattered calcification was found only in one case (5.6%). Pathological results revealed that a total of 6 (33.3%) cases had concomitant malignant carcinoma components; 2 (11.1%) patients had malignant MA; and pure MA was found in 10 cases, with a surprisingly high proportion of malignant tumours.

CONCLUSION

The positive-predictive values of "high" enhancement seemed relatively characteristic for the diagnosis of malignant and composite MA.

ADVANCES IN KNOWLEDGE

Radiopathological features of adult MA and exploring whether MA can be differentiated on CT images, including the basis of their morphological features and enhancement patterns.

Cadherin 17 is a sensitive and specific marker for metanephric adenoma

Metanephric adenoma (MA) is a rare benign renal neoplasm that shares morphologic and immunophenotypic overlap with epithelial-predominant Wilms tumor (e-WT) and with the solid variant of papillary renal cell carcinoma (s-PRCC). Cadherin 17 (CDH17) is expressed primarily in the normal intestine and digestive tract tumors and has not been detected in tumors from other sites including the kidney. We investigated the diagnostic utility of CDH17 in differentiating between MA, e-WT, and s-PRCC. Immunohistochemical analysis for CDH17, CD57, AMACR, WT-1, and CDX2 was performed on 17 e-WTs, 15 s-PRCCs, and 21 MAs and assessed on the basis of a combined score of extent and intensity. Normal adult kidney parenchyma was negative for CDH17 staining. CDH17 was expressed in the late stages of fetal kidney development at the junction of the glomerular space and proximal nephron. The majority of MAs (81%) demonstrated membranous CDH17 immunoreactivity in all components (acinar, tubular, and papillary), whereas all cases of e-WTs and s-PRCCs were negative (P<0.0001). WT-1 was negative in s-PRCC and was positive in all cases of e-WT and MA. All MAs were strongly positive for CD57; however, this marker was also moderate to strongly positive in 6 (35%) e-WTs and 2 (13%) s-PRCCs. AMACR was strongly positive in all s-PRCCs, but moderate reactivity was seen in 3 (17%) e-WTs and 2 MAs (10%). CDH17 is a sensitive (81%) and highly specific (100%) marker for MA and should be considered in the immunohistochemistry panel for distinguishing MA from its mimics.

BRAF mutations in pediatric metanephric tumors

Metanephric neoplasms of the kidney are uncommon, and some cases are associated with papillary carcinoma. Most cases of metanephric adenoma occur in adults, with fewer than 25 cases reported in children, and metanephric adenofibroma is even less common. The few metanephric tumors studied at the genetic level have not shown the gains of chromosomes 7 and 17 commonly seen in renal cell carcinoma, suggesting that the carcinoma arising in this setting has a separate genetic origin from the adenoma. However, the assumption that this carcinoma has the same chromosome gains as sporadic renal cell carcinoma has never been validated. We studied 4 cases of metanephric tumors in children, including 1 metanephric adenofibroma with papillary carcinoma. The composite tumor was studied by single nucleotide polymorphism array and fluorescence in situ hybridization, with the adenoma and carcinoma components analyzed separately. No copy number alterations were detected in either component. A BRAF V600E mutation has been reported in most cases of metanephric adenoma in adults. We performed BRAF V600E immunostaining and sequencing in our 4 pediatric cases. Three cases had a BRAF V600E mutation including the composite tumor, with both the adenoma and carcinoma components showing the same mutation. This finding provides the first genetic evidence that these 2 tumors are biologically linked. Ten cases each of pediatric renal cell carcinoma and Wilms tumor were immunonegative. Thus, BRAF V600E immunostaining is a helpful marker for pediatric metanephric adenoma, and additional research is required on the possible role of this mutation in the development of renal carcinoma.

Fine-needle aspiration of metanephric adenoma of the kidney with clinical, radiographic and histopathologic correlation: a review

Metanephric adenoma of the kidney is an uncommon benign epithelial neoplasm with only a small number of reports that describe its cytologic features. We describe two additional cases of metanephric adenoma diagnosed on fine-needle aspiration biopsy and review the available literature. Our cases showed similar cytology and were composed of cellular smears with numerous clusters of small, oval to round cells arranged in a microfollicular pattern and papillary configurations. The tumor cells had scant cytoplasm, fine chromatin and absent nucleoli. Psamomma bodies, nuclear atypia, cellular cpleomorphism, necrosis, and mitoses were absent. Because of the rarity of this tumor and the common cytologic features it shares with other lesions, including malignant tumors such as Wilms' tumor and papillary renal cell carcinoma, awareness of the cytologic features of metanephric adenoma may aid in avoiding a diagnosis of malignancy, especially preoperatively, and in guiding the proper management for the patients.

BRAF mutations in metanephric adenoma of the kidney

BACKGROUND

Metanephric adenoma (MA) of the kidney is a rare, indolent tumor that may be difficult to differentiate from other small renal masses (SRMs). Genetic alterations associated with MA remain largely unknown.

OBJECTIVE

We aimed at defining genetic events in MA of the kidney and determining their influence in the management of this disease.

DESIGN, SETTING, AND PARTICIPANTS

Multiplexed mass spectrometric genotyping was performed on 29 MA cases after tumor DNA extraction. We also conducted a mutational screen in an additional 129 renal neoplasms. Immunohistochemistry was performed on the MA cases to assess molecular markers of signaling pathway activation. Patients' baseline characteristics, as well as follow-up data, were captured.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

We used descriptive statistics for baseline clinical characteristics and incidence of mutations. The Wilcoxon rank-sum test was used to correlate patient characteristics with mutational status.

RESULTS AND LIMITATIONS

We identified the v-raf murine sarcoma viral oncogene homolog B1 (BRAF) V600E mutation in 26 of 29 MA cases. These results were validated in all cases using the commercially available BRAF Pyro Kit (QIAGEN). In contrast, BRAF mutations were rare in the other 129 non-MA renal neoplasms that were screened. We detected a BRAF mutation (V600E) in only one papillary renal cell carcinoma case. In all MA tumors, we documented expression of phosphorylated mitogen-activated protein kinase and phosphorylated extracellular signal-regulated kinase, accompanied by immunoreactivity for p16 (INK4a). All patients were treated with a partial or radical nephrectomy, and after a median follow-up of 26.5 mo, there were no local or distant recurrences. Limitations include the retrospective nature of this study.

CONCLUSIONS

BRAF V600E mutations are present in approximately 90% of all MA cases, serving as a potential valuable diagnostic tool in the differential diagnosis of SRMs undergoing a percutaneous biopsy. The presence of BRAF V600E and mitogen-activated protein kinase activation in a largely benign tumor supports the necessity for secondary events (e.g., p16 loss) in BRAF-driven oncogenesis.