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

Metanephric adenoma diagnosed on biopsy in an infant: a case report

BACKGROUND

Metanephric adenoma is a rare benign renal tumor of the kidney, uncommonly observed in children. It is often misdiagnosed preoperatively as a malignant neoplasm, leading to an unnecessary nephrectomy. The challenge is to make the right diagnosis preoperatively and therefore manage it with conservative surgery. We report a case of a child with metanephric adenoma who underwent nephron-sparing surgery.

CASE PRESENTATION

A renal tumor was discovered fortuitously in an 18-month-old Caucasian girl with several congenital malformations. Investigations showed a 28 × 27 × 27 mm left renal mass centrally located, well defined, nonvascularized, with no calcifications and which compressed the adjacent renal tissue. Furthermore, there were no signs of metastasis. The decision of a multidisciplinary meeting was to perform a computed tomography (CT)-scan-guided biopsy. Histologic examination concluded it was a metanephric adenoma. We performed a left open partial nephrectomy via a flank retroperitoneal incision. The final histopathological examination confirmed the diagnosis. The postoperative course was uneventful.

CONCLUSION

Preoperative diagnosis of metanephric adenoma is challenging. Because of the high probability of unnecessary radical nephrectomy, preoperative biopsy can be safe and determining to guide a more conservative approach so nephron-sparing surgery can be performed.

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.

Differential diagnostic value of periampullary mass: A nomogram established by random forest based on clinical characteristics and contrast-enhanced ultrasound

PURPOSES

To develop a nomogram model for distinguishing benign from malignant ampullary lesions more intuitive and accurate.

MATERIALS AND METHODS

A total of 124 patients with periampullary lesions from January 2016 to June 2020 were enrolled in this retrospective study. Their clinical information, ultrasound (US), dual contrast-enhanced ultrasound (DCEUS) and MRI image features were used for research. Twenty features were collected in our study. Random forest was used to select the first five most important indicators to construct the prediction model.

RESULTS

Patients' age, common bile duct (CBD) diameter, the shape, vascularity, and boundary of lesion, lesion size with or without enlarged after CEUS, the enhancement patterns of arterial phase, the washout patterns of venous phase, CEUS diagnosis, and MRI diagnosis were statistically significant (p < 0.05). After screening for statistically significant indicators by random forest, the first five most important indicators were age, CBD diameter, the enhancement patterns of arterial phase, the washout patterns of venous phase, lesion size with or without enlarged after CEUS, which were used to construct nomogram. The area under curves (AUC) and 95% confidence intervals (CI) for nomogram, MRI + MRCP + DCEUS, DCEUS, MRI + MRCP were 0.98(0.94-1.00), 0.91(0.84-0.97), 0.89(0.80-0.98), 0.68(0.60-0.77), respectively. The sensitivity and specificity were 100.00% and 84.62% for nomogram, 88.29% and 92.31% for MRI + MRCP+DCEUS, 86.49% and 92.31% for DCEUS, 51.35%, and 100.00% for MRI + MRCP.

CONCLUSIONS

We combined clinical indicators, gray-scale ultrasound characteristics, and CEUS characteristics to build the nomogram, which can be intuitively and accurately used for preoperative malignant prediction of ampullary lesion patients, worthy of clinical generalizability and application.

Case Report: MRI, CEUS, and CT Imaging Features of Metanephric Adenoma with Histopathological Correlation and Literature Review

The metanephric adenoma is an extremely rare, benign, embryonal-epithelial neoplasm of the kidney and has a good prognosis with appropriate treatment. It can present at any age and is often asymptomatic. Histologically, the lesion is well established; however, there have been only a few cases described with available detailed imaging findings, most of them with large renal masses typically depicted by computed tomography (CT). This case report includes imaging of contrast-enhanced MRI, contrast-enhanced ultrasound (CEUS), and CT, and thus adds to the information available, potentially promoting a nephron-sparing clinical pathway. We report on the clinical presentation, imaging, histopathological diagnosis, and treatment data of a 27-year-old female, in whom an incidental, symptomatic kidney tumor was detected. CT, CEUS, and MRI showed a suspicious unifocal renal lesion with inhomogeneous enhancement, which was indistinguishable from renal cell carcinoma. After laparoscopic resection, a metanephric adenoma with microscopically partially glandular, partially nest-like solid growth and without distinctive atypia was diagnosed pathohistologically. Immunohistochemistry results were positive for Wilms Tumor 1 and CD57 and negative for EMA and CK7: 2–3% positive cells in MIB1 coloring. At 3-month and 1-year follow-up, the patient was asymptomatic and imaging showed no recurrence of renal masses or metastases.

Adenoma metanéfrico: diagnóstico diferencial del carcinoma urotelial del tracto urinario superior. Reporte de un caso

Introduction: Metanephric adenoma is a rare benign kidney tumor. Patients with these tumors are usually asymptomatic, although polycythemia occurs in up 12% of cases. These masses are often described on diagnostic imaging as solid, single, well-defined, oval-shaped, unilateral lesions, located primarily in the renal medulla and without extrarenal involvement. These neoplasms are difficult to differentiate from malignant neoplasms of the upper urinary tract, so the definitive diagnosis is achieved by histopathology. Currently, the treatment of choice is radical nephrectomy. Case presentation: A 51-year-old woman from Bogotá (Colombia) was referred to the urology service of a tertiary care hospital due to bilateral lumbar pain of non-specific characteristics. At the time of consultation, the patient was asymptomatic. Renal and urinary tract ultrasound showed hydronephrosis and right renal mass. Computed tomography urography was requested, which revealed a lesion in the right renal pelvis with parenchymal invasion highly suggestive of high-risk upper urinary tract urothelial carcinoma, as well as adenopathies in the para-aortic lymph nodes. The patient underwent a radical nephroureterectomy with bladder cuff, which allowed establishing a final diagnosis of metanephric adenoma according to the histopathological study. Conclusions: Metanephric adenoma is a rare tumor that is difficult to diagnose through imaging, so it is necessary to explore additional tools to establish an accurate pre-surgical diagnosis that allows preserving the affected renal unit. Also, given their non-specificity, these tumors should be included in the differential diagnosis of lesions suggestive of upper tract urothelial carcinoma.

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.

Co-mutations of epidermal growth factor receptor and BRAF in Chinese non-small cell lung cancer patients

Background

Epidermal growth factor receptor (EGFR) and BRAF are 2 driver genes in non-small cell lung cancer (NSCLC) which are normally mutually exclusive. It has been previously reported that the existence of BRAF V600E in EGFR-mutated NSCLC patients could cause resistance to EGFR tyrosine kinase inhibitors (TKIs), but the influence of other BRAF actionable mutations on resistance to EGFR-TKIs has not yet been investigated. Understanding the coexistence of EGFR and BRAF actionable mutations in Chinese NSCLC patients may be essential for further treatment and prognostic prediction.

Methods

A total of 127 Chinese NSCLC patients harboring EGFR and BRAF co-mutations were enrolled in this study. We analyzed the mutation profiles of these patients through next-generation sequencing (NGS). We explored the associations between somatic mutations and patient characteristics, including tumor stage and age, among others.

Results

The frequency of EGFR and BRAF co-mutation was 0.91% in Chinese NSCLC patients, compared with 0.97% in Western NSCLC patients (cBioPortal). Among the 127 patients with both EGFR and BRAF mutations, 93 of them harbored clinically significant mutations. The remaining 34 patients were found to have mutations of uncertain significance of either EGFR or BRAF. TP53 was the most frequently mutated gene in BRAF and EGFR co-mutation patients, accounting for around 58% (N=54/93). MET active mutations (amplification and exon 14 skipping) accounted for 12% (N=11/93). Approximately 18% of patients (N=17/93) with significant EGFR mutations were detected to have fusions/rearrangements of the BRAF gene. BRAF fusion was more likely detected in EGFR exon19del patients compared with non-exon19del patients (P value =0.015). In addition, EGFR T790M, the most TKI-resistant mutation, was not found in any patient with BRAF fusion/rearrangement.

Conclusions

This study is the first to show different subtypes of EGFR and BRAF co-mutations in Chinese NSCLC patients. The prognosis of EGFR-TKI treatment may vary according to different BRAF actionable mutations. Aside from BRAF V600E, class II/III and BRAF fusions were found, which provides clues for investigating the resistance mechanisms of EGFR-TKIs in the future.

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.

New developments in existing WHO entities and evolving molecular concepts: The Genitourinary Pathology Society (GUPS) update on renal neoplasia

The Genitourinary Pathology Society (GUPS) reviewed recent advances in renal neoplasia, particularly post-2016 World Health Organization (WHO) classification, to provide an update on existing entities, including diagnostic criteria, molecular correlates, and updated nomenclature. Key prognostic features for clear cell renal cell carcinoma (RCC) remain WHO/ISUP grade, AJCC/pTNM stage, coagulative necrosis, and rhabdoid and sarcomatoid differentiation. Accrual of subclonal genetic alterations in clear cell RCC including SETD2, PBRM1, BAP1, loss of chromosome 14q and 9p are associated with variable prognosis, patterns of metastasis, and vulnerability to therapies. Recent National Comprehensive Cancer Network (NCCN) guidelines increasingly adopt immunotherapeutic agents in advanced RCC, including RCC with rhabdoid and sarcomatoid changes. Papillary RCC subtyping is no longer recommended, as WHO/ISUP grade and tumor architecture better predict outcome. New papillary RCC variants/patterns include biphasic, solid, Warthin-like, and papillary renal neoplasm with reverse polarity. For tumors with 'borderline' features between oncocytoma and chromophobe RCC, a term "oncocytic renal neoplasm of low malignant potential, not further classified" is proposed. Clear cell papillary RCC may warrant reclassification as a tumor of low malignant potential. Tubulocystic RCC should only be diagnosed when morphologically pure. MiTF family translocation RCCs exhibit varied morphologic patterns and fusion partners. TFEB-amplified RCC occurs in older patients and is associated with more aggressive behavior. Acquired cystic disease (ACD) RCC-like cysts are likely precursors of ACD-RCC. The diagnosis of renal medullary carcinoma requires a negative SMARCB1 (INI-1) expression and sickle cell trait/disease. Mucinous tubular and spindle cell carcinoma (MTSCC) can be distinguished from papillary RCC with overlapping morphology by losses of chromosomes 1, 4, 6, 8, 9, 13, 14, 15, and 22. MTSCC with adverse histologic features shows frequent CDKN2A/2B (9p) deletions. BRAF mutations unify the metanephric family of tumors. The term "fumarate hydratase deficient RCC" ("FH-deficient RCC") is preferred over "hereditary leiomyomatosis and RCC syndrome-associated RCC". A low threshold for FH, 2SC, and SDHB immunohistochemistry is recommended in difficult to classify RCCs, particularly those with eosinophilic morphology, occurring in younger patients. Current evidence does not support existence of a unique tumor subtype occurring after chemotherapy/radiation in early childhood.

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.

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.

Update on Renal Neoplasms: Clinicopathologic-Radiologic Correlation With Case-Based Examples

OBJECTIVE. This article provides a brief overview of the clinicopathologic and radiologic correlation of 12 renal neoplasms, encompassing the conventional subtypes of renal cell carcinoma and a few of the newly recognized subtypes from the 2016 World Health Organization classification of renal tumors. In addition, we touch upon infrequent neoplasms that may enter the differential diagnosis of a renal mass, with corresponding radiologic and gross images and histologic findings of case-based examples. CONCLUSION. Familiarity with the radiologic and pathologic characteristics of renal cell carcinoma and other renal neoplasms is important to correctly identify and treat these masses.