Metanephric adenoma, nephrogenic rests, and Wilms' tumor: a histologic and immunophenotypic comparison

FBLN5 as One Presumably Prognostic Gene Potentially Modulating Tumor Immune Microenvironment for Renal Clear Cell Carcinoma in Children and Young Adults

Objective

To investigate the role of FBLN5in renal clear cell carcinoma (KIRC), in particular on the tumor's immune microenvironment, including children and young adults.

Methods

FBLN5 expression in tumor and normal samples was explored using SangerBox, TIMER2.0, GEPIA, UALCAN, HPA databases. The Linkedomics database was used to obtain FBLN5 co-expressed genes in KIRC tissue. SangerBox was also used to estimate immune infiltration of FBLN5 in KIRC. The Kaplan-Meier plotter was used to investigate the survival effects of FBLN5 expression in the presence of immune infiltration. We then collected 48 cases from 7 hospitals over a-20 year period to calculate the impact of FBLN5 on the prognosis of children and young adults with KIRC.

Results

FBLN5 expression was significantly reduced in KIRC tissue compared to normal adjacent tissue. FBLN5 was potentially involved in the immune-related biological processes. In addition, FBLN5 expression has been linked to a number of immune checkpoints, cytokines, chemokines and chemokine receptors in KIRC. At the same time, the expression of FBLN5 affected the survival rates differently in KIRC patients with high or low levels of immune infiltration. High expression of FBLN5 in children and young adults with KIRC was associated with a favorable prognosis.

Conclusion

This study shed light on the potential of FBLN5 as a prognostic marker in children and young adults with KIRC and as an immune-related target for clinical treatment.

Metanephric adenoma in children: A case report and literature review

Metanephric adenoma (MA) is a rare type of benign renal epithelial tumor that can develop at any age. Nonetheless, MA is extremely rare in children and only a few cases have been reported to date. The present study aimed to report the case of a 5-year-old female found to have a mass in the right kidney during a routine pre-enrollment physical examination. Computed tomography (CT) images revealed multiple high-density calcifications in the mass, and contrast-enhanced CT and magnetic resonance imaging demonstrated that the mass was significantly enhanced in the cortical phase and decreased in the medullary phase. Based on these findings, the mass was initially diagnosed as angiomyolipoma before surgery; however, postoperative pathology confirmed the mass to be a MA. MAs are typically a type of soft tissue mass with relatively uniform density or signal, showing delayed enhancement in contrast-enhanced scanning. However, the mass found in the present study presented diffused high-density calcification, which was obvious in the early phase of contrast-enhanced scanning but weakened in the delayed enhancement phase. In conclusion, the present case study demonstrated that MA should be considered as one of the imaging differential diagnoses of fat-poor angiomyolipoma, renal carcinoma and oncocytoma.

Atypical metanephric adenoma: Shares similar histopathological features and molecular changes of metanephric adenoma and epithelial-predominant Wilms’ tumor

Background

Metanephric adenomas (MAs) are rare, benign renal tumors. Wilms’ tumors (WTs) are malignant embryonic tumors that originated from nephrogenic blastemal cells. However, some tumors have similar morphology to both MA and epithelial-predominant WT, which makes differential diagnosis difficult. We aimed to analyze the morphological, immunophenotypic and molecular changes in overlapping cases to explore their attribution.

Methods and results

Twenty MAs, ten WTs, and nine cases with MA/WT overlapping histological features were studied. Twenty tumors demonstrated the typical morphological spectrum of MA with high cellularity and were composed of tightly packed small, uniform, round acini with a lower Ki67 index. Almost all MAs (94.7%, 18/19) were detected with BRAF V600E mutation. The ten WTs were epithelial-predominant WTs with glands, rosettes and glomerular structures, which also showed a higher Ki-67 index (up to 60%), invasive growth patterns, and a lack of BRAF mutation. However, the other nine overlapping cases showed two components: typical MA-like areas and epithelial WT-like areas. The cells of the WT-like areas were tubular, columnar and showed marked cytological atypia, with a Ki-67 proliferative index of up to 30%. The immunophenotype of these overlapping lesions was not significantly different from that of typical MA and they positively expressed WT1 and CD57. The BRAF V600E mutation was detected in both WT-like and MA-like areas in nine overlapping tumors. The follow-up data of 31 patients were analyzed, with a median follow-up time of 66 months (range, 8-45 months). Even though most patients with WT underwent radiotherapy or chemotherapy after surgery, two died, and one had liver metastasis. No MA or overlapping cases showed any evidence of recurrence or metastasis after surgery.

Conclusions

The molecular changes in tumors with overlapping morphological features were the same as those of typical MA; thus, we think that these tumors should be classified as MA and further called atypical MA. It is important to note that atypical MA is not a neglected subtype of MA. It possesses different histological morphology and a higher Ki-67 index but has the common imaging characteristics, immunophenotype and gene expression as typical MA, and patients usually have a good prognosis.

Evaluating Established Roles, Future Perspectives and Methodological Heterogeneity for Wilms’ Tumor 1 (WT1) Antigen Detection in Adult Renal Cell Carcinoma, Using a Novel N-Terminus Targeted Antibody (Clone WT49)

Renal cell carcinoma (RCC) is arguably the deadliest form of genitourinary malignancy and is nowadays viewed as a heterogeneous series of cancers, with the same origin but fundamentally different metabolisms and clinical behaviors. Immunohistochemistry (IHC) is increasingly necessary for RCC subtyping and definitive diagnosis. WT1 is a complex gene involved in carcinogenesis. To address reporting heterogeneity and WT1 IHC standardization, we used a recent N-terminus targeted monoclonal antibody (clone WT49) to evaluate WT1 protein expression in 56 adult RCC (aRCC) cases. This is the largest WT1 IHC investigation focusing exclusively on aRCCs and the first report on clone WT49 staining in aRCCs. We found seven (12.5%) positive cases, all clear cell RCCs, showing exclusively nuclear staining for WT1. We did not disregard cytoplasmic staining in any of the negative cases. Extratumoral fibroblasts, connecting tubules and intratumoral endothelial cells showed the same exclusively nuclear WT1 staining pattern. We reviewed WT1 expression patterns in aRCCs and the possible explanatory underlying metabolomics. For now, WT1 protein expression in aRCCs is insufficiently investigated, with significant discrepancies in the little data reported. Emerging WT1-targeted RCC immunotherapy will require adequate case selection and sustained efforts to standardize the quantification of tumor-associated antigens for aRCC and its many subtypes.

Metanephric adenoma: molecular study and review of the literature

Introduction: Metanephric adenoma (MA) is an uncommon benign tumor accounting for 0.2–0.7% of adult renal epithelial neoplasms. The clinical course is often indolent, but diagnosis should not be delayed since clinical symptoms (hematuria, fever, palpable abdominal mass, and flank pain) may be non-specific and overlap with those of a malign renal neoplasm. We report on 4 cases of AM, for which morphological and mutational analysis were performed.

Material and Methods: Immunohistochemical staining was performed on sections cut from paraffin blocks to assess expression of WT1, vimentin, racemase, CK7, CD10 and RCC. Testing for the BRAF gene mutation V600 was carried out using real-time PCR (Cobas^® 4800).

Results: In all four cases, tumors were visible as well-circumscribed, non-encapsulated masses located in the renal cortex and extending towards the medulla. At immunohistochemical examination, tumor cells stained negative for CK7, CD10 and RCC and positive for both WT1 (nuclear, intense) and vimentin (cytoplasmic, intense, and diffuse). Molecular analysis revealed the BRAF gene mutation V600E in three cases and wild-type BRAF in the fourth.

Conclusions: BRAF molecular mutation analysis may aid diagnosis in cases with atypical histological features, especially in small incisional biopsies when reassessment of surgical treatment may be considered.

[Metanephric adenoma, a benign variant of Wilms' tumour: case report of an extremely rare kidney tumour and literature survey]

Rare benign tumours of the kidney comprise a group of very different histogenetic entities. We report a case of a 53-year-old woman who underwent laparoscopic nephrectomy because of a renal mass. The diagnosis of a rare and benign metanephric adenoma was confirmed by histopathology. With less than 200 documented cases, the metanephric adenoma described here is a rarity in everyday urological practice and cannot be distinguished from a malignant tumour of the kidney by clinical examination and/or imaging without histological assessment.

Reevaluation of metanephric stromal tumor two decades after it was named: A narrative review

OBJECTIVE

The aim of this narrative review is to provide an overview and update of metanephric stromal tumor (MST).

MATERIALS AND METHODS

All English language studies published from January 1, 2000 to December 31, 2019 in PubMed, EBSCO, Elsevier ScienceDirect, Springer Link and Taylor & Francis databases were searched with the search terms "metanephric stromal tumor" for this review.

RESULTS

Seventeen eligible case reports representing 47 patients according to inclusion and exclusion criteria were included in this study. The average age of the patients was under 4 years (range from 2 d to 56 y) and over half of the cases (52.1%, 25/47) are were diagnosed as MST by accident or during examinations for other diseases. Morphologically, tumor specimens of almost all cases presented concentric "onion-skin cuffing" or characteristic collarettes around renal tubules under low power. There were 79.2% (18/25) of patients exhibited BRAF V600E mutations. Immunohistochemistry (IHC) is characterized by CD34 (+), Vimentin (+), Desmin (-), S-100 (-), SMA (-). Most patients underwent surgeries, and no metastasis or recurrence was found except for one case.

CONCLUSION

MST is a rare benign pediatric renal tumor with surgical treatment as the first choice. CT examinations and ultrasonography are two widely accepted techniques for the diagnosis of MST. Percutaneous renal biopsy (PRB) is an effective and accurate way of preoperative diagnosis, however, it is not recommended for children under 10 years or with a cystic mass in CT images. The relationship between BRAF V600E mutations and mild clinical manifestations of MST is in need of further verification by biological experiments and clinical studies.

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.

ADVL1522: A phase 2 study of lorvotuzumab mertansine (IMGN901) in children with relapsed or refractory wilms tumor, rhabdomyosarcoma, neuroblastoma, pleuropulmonary blastoma, malignant peripheral nerve sheath tumor, or synovial sarcoma-A Children's Oncology Group study

BACKGROUND

Lorvotuzumab mertansine (IMGN901) is an antibody-drug conjugate linking an antimitotic agent (DM1) to an anti-CD56 antibody (lorvotuzumab). Preclinical efficacy has been noted in Wilms tumor, rhabdomyosarcoma, and neuroblastoma. Synovial sarcoma, malignant peripheral nerve sheath tumor (MPNST), and pleuropulmonary blastoma also express CD56. A phase 2 trial of lorvotuzumab mertansine was conducted to assess its efficacy, recommended phase 2 dose, and toxicities.

METHODS

Eligible patients had relapsed after or progressed on standard therapy for their tumor type. Lorvotuzumab mertansine (110 mg/m² per dose) was administered at the adult recommended phase 2 dose intravenously on days 1 and 8 of 21-day cycles. Dexamethasone premedication was used. Pharmacokinetic samples, peripheral blood CD56-positive cell counts, and tumor CD56 expression were assessed.

RESULTS

Sixty-two patients enrolled. The median age was 14.3 years (range, 2.8-29.9 years); 35 were male. Diagnoses included Wilms tumor (n = 17), rhabdomyosarcoma (n = 17), neuroblastoma (n = 12), synovial sarcoma (n = 10), MPNST (n = 5), and pleuropulmonary blastoma (n = 1). Five patients experienced 9 dose-limiting toxicities: hyperglycemia (n = 1), colonic fistula (n = 1) with perforation (n = 1), nausea (n = 1) with vomiting (n = 1), increased alanine aminotransferase in cycle 1 (n = 2), and increased alanine aminotransferase in cycle 2 (n = 1) with increased aspartate aminotransferase (n = 1). Non-dose-limiting toxicities (grade 3 or higher) attributed to lorvotuzumab mertansine were rare. The median values of the maximum concentration, half-life, and area under the curve from zero to infinity for DM1 were 0.87 µg/mL, 35 hours, and 27.9 µg/mL h, respectively. Peripheral blood CD56+ leukocytes decreased by 71.9% on day 8. One patient with rhabdomyosarcoma had a partial response, and 1 patient with synovial sarcoma achieved a delayed complete response.

CONCLUSIONS

Lorvotuzumab mertansine (110 mg/m² ) is tolerated in children at the adult recommended phase 2 dose; clinical activity is limited.

Experience of diagnosis and management of metanephric adenoma: retrospectively analysis of 10 cases and a literature review

Background

Metanephric adenoma (MA) is a rare benign tumor with only several hundred cases reported worldwide to date. Herein, we retrospectively summarized the experience of diagnosis and management of ten MA cases.

Methods

A total of ten MA patients were included in this study definitely diagnosed by postoperative immunohistochemistry at the First Affiliated Hospital of Nanjing Medical University from January 2010 to January 2019. Clinical characteristics, image features, therapeutic procedures, histological diagnosis and outcomes of them were retrospectively analyzed.

Results

Characteristics of the patient population were nine females and one male with age of 36.8±17.5 years. The mean tumor size was 33.6 mm (range from 35.0 to 70.0 mm). Among them, nine cases were asymptomatic and one case showed acute flank pain. All ten cases underwent plain and enhanced computed tomography (CT) scan. Laparoscopic partial nephrectomy (LPN) was performed in seven cases and laparoscopic radical nephrectomy (LRN) was applied in the other three cases. Postoperative routine pathology results confirmed that seven cases were MA. However, two patients were misdiagnosed with papillary renal cell carcinoma (PRCC), and another was misdiagnosed with Wilms’ tumor. Further immunohistochemistry eventually confirmed all these ten cases as MA. During a mean follow-up of 58.3 month, all ten patients were alive with no local recurrences nor metastases.

Conclusions

In summary, MA is a rare benign tumor with no distinct clinical symptoms. The definite diagnosis depends on the postoperative pathological findings. Fortunately, due to its non-malignant nature, patients always have a good prognosis.

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.

Renal Tumors of Childhood-A Histopathologic Pattern-Based Diagnostic Approach

Renal tumors comprise approximately 7% of all malignant pediatric tumors. This is a highly heterogeneous group of tumors, each with its own therapeutic management, outcome, and association with germline predispositions. Histopathology is the key in establishing the correct diagnosis, and therefore pathologists with expertise in pediatric oncology are needed for dealing with these rare tumors. While each tumor shows different histologic features, they do have considerable overlap in cell type and histologic pattern, making the diagnosis difficult to establish, if based on routine histology alone. To this end, ancillary techniques, such as immunohistochemistry and molecular analysis, can be of great importance for the correct diagnosis, resulting in appropriate treatment. To use ancillary techniques cost-effectively, we propose a pattern-based approach and provide recommendations to aid in deciding which panel of antibodies, supplemented by molecular characterization of a subset of genes, are required.

Biphasic squamoid alveolar renal carcinoma with positive CD57 expression: A clinicopathologic study of three cases

Biphasic squamoid alveolar renal cell carcinoma (BSARCC) is a rare and recently characterized form of papillary renal cell carcinoma (PRCC). Herein, we describe three cases of BSARCC that were CD57+. Among a total of 90 cases of PRCC, three cases were found to be consistent with a diagnosis of BSARCC. In addition to reviewing these cases, we reviewed the relevant literature pertaining to this form of cancer and assessed the immunohistochemical staining for CD57 on the available tumor samples. The three BSARCC cases in the present study were composed of two primary populations of cells. Tumors stained positive for CK, PAX8, CK7, CK19, AMACR, EMA, and vimentin. Larger cells expressed detectable levels of cyclin D1, and expression of CD57 was limited to the larger cells. All three patients were alive and free of disease during the most recent follow-up. Our results suggest that the CD57 positivity of at least a subset of cases should necessitate their differentiation from cases of metanephric adenoma.

Novel clinicopathological and molecular characterization of metanephric adenoma: a study of 28 cases

Background

Metanephric adenoma is a rare, benign renal neoplasm with occasional misdiagnosis. However, its molecular characterization is not fully understood.

Methods

In this study, we use the hybrid capture-based Next-Generation Sequencing to sequence a panel of 295 well-established oncogene or tumor suppressor genes in 28 cases of MA patients in China. Novel clinicopathological markers associated with the mitogen-activated protein kinase (MAPK) pathway in metanephric adenoma were detected by immunohistochemistry.

Results

It was found that except for BRAF (22/28) mutations (c.1799 T > A, p.V600E), NF1 (6/28), NOTCH1 (5/28), SPEN (5/28), AKT2 (4/28), APC (4/28), ATRX (3/28), and ETV4 (3/28) mutations could also be detected. Meanwhile, a novel and rare gene fusion of STARD9-BRAF, CUX1-BRAF, and LOC100507389-BRAF was detected in one MA patient. In addition, although MEK phosphorylation was normally activated, the phosphorylation level of ERK was low in metanephric adenoma cases. Highly expressed p16 and DUSP6 may have contributed to these results, which maintained MA as a benign renal tumor.

Conclusions

This study provides novel molecular and pathological markers for metanephric adenoma, which could improve its diagnosis and increase the understanding of its pathologic mechanism.

Electronic supplementary material

The online version of this article (10.1186/s13000-018-0732-x) contains supplementary material, which is available to authorized users.

The first investigation of Wilms' tumour atomic structure-nitrogen and carbon isotopic composition as a novel biomarker for the most individual approach in cancer disease

The paper describes a novel approach to investigating Wilms' tumour (nephroblastoma) biology at the atomic level. Isotope Ratio Mass Spectrometry (IRMS) was used to directly assess the isotope ratios of nitrogen and carbon in 84 Wilms' tumour tissue samples from 28 cases representing the histological spectrum of nephroblastoma. Marked differences in nitrogen and carbon isotope ratios were found between nephroblastoma histological types and along the course of cancer disease, with a breakout in isotope ratio of the examined elements in tumour tissue found between stages 2 and 3. Different isotopic compositions with regard to nitrogen and carbon content were observed in blastemal Wilms' tumour, with and without focal anaplasia, and in poorly- and well-differentiated epithelial nephroblastoma. This first assessment of nitrogen and carbon isotope ratio reveals the previously unknown part of Wilms' tumour biology and represents a potential novel biomarker, allowing for a highly individual approach to treating cancer. Furthermore, this method of estimating isotopic composition appears to be the most sensitive tool yet for cancer tissue evaluation, and a valuable complement to established cancer study methods with prospective clinical impact.

The findings of CT and MRI in patients with metanephric adenoma

Background

Metanephric adenoma (MA) is a benign renal tumor that is difficult to distinguish from a malignant tumor via traditional radiography. The diagnosis of MA is often dependent on postsurgical histopathological examination. In the present report, the imaging features of MA on computer tomography (CT) and magnetic resonance imaging (MRI) were retrospectively evaluated.

Methods

Eight MA patients, 17–67 years of age, were pathologically confirmed and recruited between April 2009 and November 2014. Four of the eight patients were female. All patients underwent CT scanning, and one patient underwent MRI scanning. Three patients underwent CTA of the renal arteries. All patients underwent resection surgery (radical nephrectomy in five and nephron-sparing surgery in three patients).

Results

The average tumor size was 44.0 ± 23.6 mm. The lesions in 87.5 % cases were located both in the renal cortex and medulla and exhibited exophytic growth. Plain CT showed that MA tumors were solid, and the average CT value was 37.9 ± 6.7 HU. Dynamic contrast-enhanced CT revealed that enhanced degrees of MA tumors in the renal cortex, renal parenchymal, and pelvic phase were all lower than that of normal renal parenchyma. A slight enhancement in the renal cortex phase and an even higher enhancement in the renal parenchymal phase were observed in seven of the cases. Progressive enhancement in the pelvic phase was found in five cases and a slight decreased enhancement in the pelvic phase in two cases. MRI revealed that MA tumor was isointense on T1WI and isointense on T2WI with some slightly hyperintense areas in the center. CTA of the renal arteries revealed the nutrient artery in one patient and no nutrient artery in two. Immunohistochemical experiments demonstrated that most tumor cells were positive for vimentin, CK, and EMA.

Conclusions

MA is a rare benign renal neoplasm. Detailed knowledge of the CT and MRI characteristics of MA plays an important role in MA diagnosis and treatment.

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.

Wilms Tumor: An Uncommon Entity in the Adult Patient

Wilms tumor, the most common kidney tumor in children, is rarely seen in adults, making it a challenge for the adult oncologist to diagnose and treat. Unlike with renal cell carcinoma, patients with Wilms tumor should receive adjuvant chemotherapy with or without radiation therapy. Adult oncologists may not be familiar with pediatric oncology protocols, so it is important to consult with pediatric oncologists who have more experience in this disease. Multimodal therapy based on pediatric protocols improved the outcomes of adults with Wilms tumor worldwide. We report a rare case of a 24-year-old woman with a slow-growing mass of the left kidney during a 4-year period. The mass was surgically removed and final diagnosis confirmed by pathology to be Wilms tumor. The patient received adjuvant chemotherapy and has been free of disease since 2014.

Thyroid-like follicular carcinoma of the kidney: one case report and review of the literature

OBJECTIVES

Thyroid-like follicular carcinoma of the kidney continues to confound the practicing pathologist with its close resemblance to the follicular variant of thyroid carcinoma, as well as other benign and malignant entities. Our goal is to expand the knowledge of this rare renal cell carcinoma subtype, which is morphologically similar to follicular carcinoma of the thyroid but lacks expression of characteristic thyroid immunohistochemical markers such as TTF-1 and thyroglobulin.

METHODS

We evaluated the gross, histologic, immunohistochemical, and fluorescence in situ hybridization (FISH) studies of a new case and performed a comprehensive review of the literature.

RESULTS

The lesion was spongy and well-circumscribed. Microscopically it showed variably sized follicular structures, filled with abundant, deeply eosinophilic, colloid-like material. At the periphery, it displayed areas resembling metanephric adenoma and early stages of nephrogenesis. The tumor cells strongly expressed CK7, PAX-8, PAX-2, vimentin, EMA, and CK19 immunostains. Other markers, such as CD10, RCC, HBME-1, thyroglobulin, and TTF-1, were not immunoreactive. The tumor was negative for trisomy of both 7 and 17 and showed borderline monosomies (losses) of both chromosomes in FISH studies.

CONCLUSIONS

Five years of preoperative observation and lack of recurrence bring further insight into the slow progressive nature of this neoplasm and support a low malignant potential. Proper identification is important to secure adequate treatment and follow-up.

Metanephric adenoma: the utility of immunohistochemical and cytogenetic analyses in differential diagnosis, including solid variant papillary renal cell carcinoma and epithelial-predominant nephroblastoma

Metanephric adenoma is a benign renal neoplasm that overlaps in morphology with the solid variant of papillary renal cell carcinoma and epithelial-predominant nephroblastoma. To aid in resolving this differential diagnosis, we investigated the utility of immunohistochemical and molecular analyses in distinguishing between these entities; the first study, to our knowledge, to use a combined approach in analyzing all three tumors. We analyzed 37 tumors originally diagnosed as metanephric adenomas (2 of which we reclassified as papillary renal cell carcinomas), 13 solid variant papillary renal cell carcinomas, and 20 epithelial-predominant nephroblastomas using a combination of immunohistochemistry and fluorescence in situ hybridization (FISH) assessing for trisomy of chromosomes 7 and 17 and loss of Y. Immunohistochemical staining was performed for CK7, AMACR, WT1, and CD57. The combination of CK7-, AMACR-, WT1+, and CD57+ was considered characteristic of metanephric adenoma. Most of the tumors originally diagnosed as metanephric adenomas (31/37) showed the expected staining pattern of metanephric adenoma (CK7-, AMACR-, WT1+, and CD57+). Of the six tumors with discordant immunophenotype, two tumors were reclassified as papillary renal cell carcinoma after cytogenetic workup. It is recommended that all adult cases histologically resembling metanephric adenoma have WT1, CD57, CK7, and AMACR immunohistochemical staining performed. If the staining pattern is characteristic for metanephric adenoma (CK7-, AMACR-, WT1+, and CD57+, including membranous staining), then no other diagnostic tests are indicated. However, if there is a different immunostaining pattern, then we recommend FISH analysis.

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.

Molecular and immunohistochemical characterization reveals novel BRAF mutations in metanephric adenoma

Metanephric adenoma (MA) is a rare benign renal tumor comprised of a neoplastic proliferation of primitive metanephric tubular cells. A previous study identified BRAF V600E mutations in approximately 90% of MA and found that similar BRAF exon 15 mutations are exceedingly rare in other common renal tumors, including renal cell carcinoma and oncocytoma. A recent follow-up study has validated mutation-specific immunohistochemistry (IHC) for detection of BRAF V600E mutations in a small cohort of MA. Here, we extend these findings to a larger, independent cohort of MA, demonstrating an overall 88% sensitivity and 100% specificity for BRAF V600E IHC. In addition, we report 2 cases of MA with novel BRAF exon 15 mutations, including a V600D missense mutation and a compound V600D and K601L missense mutation. Finally, we evaluate BRAF V600E IHC in a large tissue microarray cohort of common renal tumors and find no significant expression in several renal cell carcinoma subtypes. These data support a role for BRAF V600E IHC in diagnostically challenging cases of MA and expand the spectrum of BRAF exon 15 mutations in this uncommon but unique renal neoplasm.

Congenital renal tumor: metanephric adenoma, nephrogenic rest, or malignancy?

We report a renal tumor detected by prenatal ultrasound and resected at 2 months of age. This 9-cm, solid mass was composed of tubular and papillary structures lined by small, uniform epithelial cells. There was local invasion into renal parenchyma and a tumor deposit in a hilar lymph node. The tumor was immunopositive for WT1, pankeratin, and CD10; focally positive for CK7; and negative for EMA and TFE3. Based on morphology and immunophenotype, the favored diagnosis was metanephric adenoma over Wilms tumor, renal cell carcinoma, and nephrogenic rest. However, metanephric adenoma only occasionally occurs in children and has never been reported prenatally. Alternatively, this tumor might be a congenital Wilms tumor that differentiated completely. Although the nature of the tumor remains unconfirmed, resection appears to have been curative; the patient remains disease-free 18 months following surgery alone.

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.

Metanephric adenosarcoma: a rare case with immunohistochemistry and molecular analysis

Background

Metanephric neoplasms comprised a spectrum of kidney tumors containing renal epithelial or stromal cells or both, including metanephric adenoma, metanephric stromal tumor, and metanephric adenofibroma. The majority of cases were benign; only one case of “metanephric adenosarcoma” had been reported in the English literature.

History

We present the case of a 69-year-old man who developed a neoplasm composed of renal epithelial component identical to metanephric adenoma combined with malignant spindle-cell stroma. The epithelial component was positive for CD57, AE1/AE3, but negative for WT-1, CD56, SYN, and CgA; whereas the sarcomatous component was negative for epithelial markers, SMA, Caldesmon, MyoD1, Myogenin, and S-100; and positive for vimentin, CD10, and WT1 focally. No specific sarcoma differentiation was apparent in the stroma by immunohistochemistry, and no SYT-SS18 rearrangement or BRAF mutation was detected by molecular analysis.

A diagnosis of metanephric adenosarcoma was made because of the morphological features and immunohitochemistry and molecular pathology analysis.

Clinical significance

We believe that metanephric adenosarcoma should be in the expanded spectrum of metanephric neoplasia as a malignant stromal variant.

Conclusions

We report a rare case of metanephric adenosarcoma with immunohistochemistry and molecular analysis and emphasize the histopathologic features and differential diagnosis of the rare lesion to promote a better and broader understanding of this less understood subject.

Virtual Slides

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Recent advances of immunohistochemistry for diagnosis of renal tumors

The recent classification of renal tumors has been proposed according to genetic characteristics as well as morphological difference. In this review, we summarize the immunohistochemical characteristics of each entity of renal tumors. Regarding translocation renal cell carcinoma (RCC), TFE3, TFEB and ALK protein expression is crucial in establishing the diagnosis of Xp11.2 RCC, renal carcinoma with t(6;11)(p21;q12), and renal carcinoma with ALK rearrangement, respectively. In dialysis-related RCC, neoplastic cells of acquired cystic disease-associated RCC are positive for alpha-methylacyl-CoA racemase (AMACR), but negative for cytokeratin (CK) 7, whereas clear cell papillary RCC shows the inverse pattern. The diffuse positivity for carbonic anhydrase 9 (CA9) is diagnostic for clear cell RCC. Co-expression of CK7 and CA9 is characteristic of multilocular cystic RCC. CK7 and AMACR are excellent markers for papillary RCC and mucinous tubular and spindle cell carcinoma. CD82 and epithelial-related antigen (MOC31) may be helpful in the distinction between chromophobe RCC and renal oncocytoma. WT1 and CD57 highlights the diagnosis of metanephric adenoma. The combined panel of PAX2 and PAX8 may be useful in the diagnosis of metastatic RCC.

Value of PAX8, PAX2, napsin A, carbonic anhydrase IX, and claudin-4 immunostaining in distinguishing pleural epithelioid mesothelioma from metastatic renal cell carcinoma

Both mesotheliomas and renal cell carcinomas can present a wide variety of cytomorphologic features and histologic patterns. Because of this, renal cell carcinomas metastatic to the pleura and lung can be confused with mesotheliomas. Recently, a variety of positive carcinoma markers, including kidney-associated markers, have become available. The aim of this study is to investigate the value of some of these markers, specifically PAX8, PAX2, napsin A, carbonic anhydrase IX, and claudin-4, for assisting in distinguishing pleural epithelioid mesotheliomas from metastatic renal cell carcinomas. To do so, a total of 40 pleural epithelioid mesotheliomas and 55 renal cell carcinomas (33 clear cell, 10 papillary, and 12 chromophobe) were investigated. In all, 91% of the renal cell carcinomas expressed claudin-4, 89% PAX8, 60% PAX2, 71% carbonic anhydrase IX, and 29% napsin A. All of the mesotheliomas were positive for carbonic anhydrase IX and were negative for all of the other markers. On the basis of these results, it is concluded that claudin-4 and PAX8 have a higher sensitivity and specificity for assisting in discriminating between pleural epithelioid mesotheliomas and renal cell carcinomas when compared with all of the other positive carcinoma markers that are, at present, recommended to be included in the immunohistochemical panels used in this differential diagnosis. Even though PAX2 and napsin A are highly specific, because of their low sensitivity, they have only a limited value. Carbonic anhydrase IX is not useful.

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.

Composite tumor of metanephric adenoma and Wilms' tumor of the kidney: A case report and review of the literature

Metanephric adenoma (MA) and Wilms' tumor (WT) are two distinct types of renal tumors. Composite MA and WT of the kidney are extremely rare. Here, a rare case of composite MA and WT of the kidney in a 36-year-old male is described. MA and WT each have their own histopathological features, respectively, and they focally share morphological similarities, which can be a diagnostic challenge. Immunohistochemistry is useful in the differential diagnosis of MA and WT. The histopathological features and differential diagnosis of the composite tumor are emphasized here to promote a better and broader understanding of this less understood subject.

A composite renal tumor: metanephric adenofibroma, Wilms tumor, and renal cell carcinoma: a missing link?

A coexistence of different renal tumors has rarely been reported. The most commonly described association is of Wilms tumor and renal cell carcinoma. Metanephric adenofibroma has also been associated with Wilms tumor or papillary renal cell carcinoma. Another reported association is metanephric adenoma and papillary renal cell carcinoma with sarcomatoid dedifferentiation. Herein we describe a complex renal tumor containing areas of metanephric adenofibroma, Wilms tumor, and undifferentiated renal cell carcinoma in a previously healthy 18-year-old boy. The tumor showed histologic and immunohistochemical features of these 3 different tumors, offering additional support to the view that these 3 tumors are related.

Metanephric stromal tumor: a challenging diagnostic entity in children

A case with a renal mass diagnosed as metanephric stromal tumor is presented. A 6-year-old boy presented with frequently recurring urinary tract infections. He had been followed up at different medical centers for the last 2 years with a 2 × 2 cm simple cyst localized in the inferior pole of the left kidney. At our center, ultrasonography revealed a heterogeneous mass in the left kidney with a central cystic component. The patient underwent operation for left renal mass, and heminephrectomy was performed. The 5 × 4 × 2.5 cm left heminephrectomy specimen showed a partially cystic mass composed of bland spindle cells distributed haphazardly, entrapping tubules and glomeruli and producing fine collarettes around some tubules. The cysts were lined with a 1-layered flat or cuboidal epithelium. Histopathologically, the tumor was diagnosed as metanephric stromal tumor. Metanephric stromal tumor is a rare renal neoplasm of childhood that can present as a cystic mass, and the solid component can go radiologically undetected because of the blurring infiltrative margins. By presenting this rare entity, the authors suggest that this should be included in the differential diagnosis, thereby helping to avoid complications and unnecessary treatment.

Characterization of primary Wilms tumor cultures as an in vitro model

Functional analysis of gene candidates and testing of novel therapeutics in Wilms tumors (WT) has been hampered by the lack of in vitro model systems. WT are characterized by a spectrum of histological appearances, but published cell lines are mostly derived from rare anaplastic variants or even non-WT. There has been some success in establishing primary cultures, but these are often poorly characterized or only derived from less frequent WT1 mutant tumors. We report the generation of a set of primary WT-cell cultures using a simple cultivation protocol. Our cultures could be established after preoperative chemotherapy and irrespective of histological subtypes or genetic alterations. The presence of tumor-specific genetic alterations validates these cultures as being tumor-derived. Genetic characterization is of utmost importance as some cultures with similar morphological appearance lacked such alterations and either represent clonal variants or normal cells. By immunohistochemistry, the cells are either epithelial or more mesenchymal, and the latter exhibiting a longer life span with 30 or more passages before undergoing senescence. This may be related to WT being embryonal tumors with a strong differentiation potential that may prevail in vitro. Telomeres progressively shorten with cultivation, but their length does not predict lifespan. hTERT transfection may partly allow establishment of immortalized lines, because 2/7 cultures avoid senescence even in later passages. Importantly, these cells can be efficiently manipulated by transfection, making them a useful model system for in vitro testing.

Conservative treatment of metanephric adenoma. A case report and review of the literature

Metanephric adenoma (MA) is a rare kidney tumor, especially in children, with an excellent prognosis and frequent association with polycythemia. We report the case of a 4-year-old girl presenting a MA revealed by polycythemia. Any secondary polycythemia requires checking for a possible kidney tumor even when the erythropoietin level is not elevated. MA is an exclusively epithelial tumor that can be similar to nephroblastoma or papillary renal cell carcinoma; therefore, it requires strict histopathological analysis. There are few radiological characteristics of MA: well circumscribed tumor, slightly enhanced after the injection of an intravenous contrast medium on computed tomography scan or magnetic resonance imaging. Diagnosis can be supported by core-needle kidney biopsy after hemostasis check, following two published cases of associated acquired von Willebrand disease. Chemotherapy can then be avoided and first-line conservative surgical treatment by partial nephrectomy can be considered, as in our patient's case. However, the marginal resection raised the question of frozen sections analysis of the margins. We recommend thorough follow-up visits, combining clinical examination, ultrasonography and, in the case of polycythemia, biological assays.

Recurrent gross hematuria with positive family history of IgA nephropathy and an unexpected diagnosis

A 12-year-old girl presented with recurrent gross hematuria over 3 months and regular findings in sonography of the urogenital tract. The first suspected diagnosis of familial IgA glomerulonephritis was excluded by kidney biopsy. After a further episode of gross hematuria leading to vesical tamponade, the patient received magnetic resonance imaging with angiography and urography, which was suspicious for a renal tumor. Consecutively, unilateral nephrectomy was performed and a nephroblastoma was diagnosed. This case demonstrates that even in grossly normal renal ultrasound, relapsing episodes of gross hematuria can be caused by renal tumor, and therefore in unclear situations, further diagnostic is necessary.

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

Metanephric adenoma is a rare benign renal tumor typically found in adults. Previous cytogenetic analyses, including karyotyping, fluorescence in situ hybridization (FISH), and comparative genomic hybridization, have yielded conflicting results regarding the somatic genetic aberrations of these tumors. In this study, we investigated the genomic profile of nine cases of metanephric adenoma using array comparative genomic hybridization. Two cases revealed multiple chromosomal gains and losses. Three cases showed sporadic chromosomal imbalances involving no more than three chromosomes. Four cases showed normal chromosome copy numbers. The gain of chromosome 19 was the most common finding (five cases), and FISH using 19p and 19q telomeric probes further confirmed this finding. We did not observe consistent gains of chromosomes 7 and 17, which are common in papillary renal cell carcinoma, neither did we find chromosomal alterations frequently present in Wilms' tumors, including chromosome gains of 1q, 7q, and 12, and losses of 11p and 16q. Our series demonstrates that the genetic profile of metanephric adenoma is fundamentally distinct from those of papillary renal cell carcinoma and Wilms' tumor.