Diagnostic magnetic resonance imaging characteristics of congenital mesoblastic nephroma: a retrospective multi-center International Society of Pediatric Oncology-Renal Tumor Study Group (SIOP-RTSG) radiology panel study.

BACKGROUND: Congenital mesoblastic nephroma is the most common solid renal tumor in neonates. Therefore, patients <3 months of age are advised to undergo upfront nephrectomy, whereas invasive procedures at diagnosis in patients ≥3 months of age are discouraged by the International Society of Pediatric Oncology-Renal Tumor Study Group (SIOP-RTSG). Nevertheless, discriminating congenital mesoblastic nephroma, especially from the more common Wilms tumor, solely based on imaging remains difficult. Recently, magnetic resonance imaging (MRI) has become the preferred modality. Studies focusing on MRI characteristics of congenital mesoblastic nephroma are limited. OBJECTIVE: This study aims to identify diagnostic MRI characteristics of congenital mesoblastic nephroma in the largest series of patients to date. MATERIALS AND METHODS: In this retrospective multicenter study, five SIOP-RTSG national review radiologists identified 52 diagnostic MRIs of histologically proven congenital mesoblastic nephromas. MRI was performed following SIOP-RTSG protocols, while radiologists assessed their national cases using a validated case report form. RESULTS: Patients (24/52 classic, 11/52 cellular, and 15/52 mixed type congenital mesoblastic nephroma, 2/52 unknown) had a median age of 1 month (range 1 day-3 months). Classic type congenital mesoblastic nephroma appeared homogeneous with a lack of hemorrhage, necrosis and/or cysts, showing a concentric ring sign in 14 (58.3%) patients. Cellular and mixed type congenital mesoblastic nephroma appeared more heterogeneous and were larger (311.6 and 174.2 cm3, respectively, versus 41.0 cm3 for the classic type (P<0.001)). All cases were predominantly T2-weighted isointense and T1-weighted hypointense, and mean overall apparent diffusion coefficient values ranged from 1.05-1.10×10-3 mm2/s. CONCLUSION: This retrospective international collaborative study showed classic type congenital mesoblastic nephroma predominantly presented as a homogeneous T2-weighted isointense mass with a typical concentric ring sign, whereas the cellular type appeared more heterogeneous. Future studies may use identified MRI characteristic of congenital mesoblastic nephroma for validation and for exploring the discriminative non-invasive value of MRI, especially from Wilms tumor.

Imaging of fetal tumors and other dysplastic lesions: A review with emphasis on MR imaging.

Fetal tumors and other dysplastic masses are relatively rare. They are usually the result of failure of differentiation and maturation during embryonic or fetal life; dysplastic lesions may be the consequence of an obstruction sequence. In this review, we present the most commonly encountered tumors and masses seen during fetal life. Imaging characteristics, tumoral organ of origin, and its effect on the surrounding organs and overall fetal hemodynamics are descriptors that must be relayed to the fetal surgeon and maternal fetal medicine expert, in order to institute most accurate parental counseling and appropriate perinatal treatment plan.

Expanding Phenotype of Schimke Immuno-Osseous Dysplasia: Congenital Anomalies of the Kidneys and of the Urinary Tract and Alteration of NK Cells.

Schimke immuno-osseous dysplasia (SIOD) is a rare multisystemic disorder with a variable clinical expressivity caused by biallelic variants in SMARCAL1. A phenotype-genotype correlation has been attempted and variable expressivity of biallelic SMARCAL1 variants may be associated with environmental and genetic disturbances of gene expression. We describe two siblings born from consanguineous parents with a diagnosis of SIOD revealed by whole exome sequencing (WES). Results: A homozygous missense variant in the SMARCAL1 gene (c.1682G>A; p.Arg561His) was identified in both patients. Despite carrying the same variant, the two patients showed substantial renal and immunological phenotypic differences. We describe features not previously associated with SIOD-both patients had congenital anomalies of the kidneys and of the urinary tract and one of them succumbed to a classical type congenital mesoblastic nephroma. We performed an extensive characterization of the immunophenotype showing combined immunodeficiency characterized by a profound lymphopenia, lack of thymic output, defective IL-7Rα expression, and disturbed B plasma cells differentiation and immunoglobulin production in addition to an altered NK-cell phenotype and function. Conclusions: Overall, our results contribute to extending the phenotypic spectrum of features associated with SMARCAL1 mutations and to better characterizing the underlying immunologic disorder with critical implications for therapeutic and management strategies.

Renal Tumors of Childhood: Radiologic-Pathologic Correlation Part 1. The 1st Decade: From the Radiologic Pathology Archives.

Wilms tumor is the second most common pediatric solid tumor and by far the most common renal tumor of infants and young children. As most tumors are large at presentation and are treated with nephrectomy, the role of imaging is primarily in preoperative planning and evaluation for metastatic disease. However, with treatment protocols increasingly involving use of preoperative (neoadjuvant) chemotherapy (the standard in Europe) and consideration of nephron-sparing surgery, the role of imaging is evolving to include providing initial disease staging information and a presumptive diagnosis to guide therapy. Differential diagnostic considerations include lesions that are clinically benign and others that require more intensive therapy than is used to treat Wilms tumor. In part 1 of this article, the unique histologic spectrum of renal neoplasms of infants and young children is reviewed with emphasis on radiologic-pathologic correlation. Part 2 will focus on renal tumors of older children and adolescents.

Congenital mesoblastic nephroma: Its diverse clinical features - A literature review with a case report.

To characterise congenital mesoblastic nephroma (CMN), with special emphasis on polyhydramnios and the neonatal prognosis, we summarise 31 CMN patients (30 reported patients and the present patient). CMN was detected at a median of 30 weeks' gestation, and infants were delivered at a median of 34 weeks' gestation. Of 27 patients with available data, 19 (70%) had polyhydramnios, of which 8 required amnio- drainage. Women with amnio-drainage gave birth significantly earlier (30.4 weeks' gestation) than those without polyhydramnios (36.7 weeks' gestation). Thus, CMN was frequently associated with polyhydramnios and this polyhydramnios was associated with a significant increase in the risk of preterm birth. Of 20 patients with available data, the affected-side kidney was 'compressed' in 16 and 'replaced' in 4: polyhydramnios was present in a half vs 100%, respectively, suggesting that a 'replaced' kidney may suggest a more aggressive tumour and may be associated with a poorer prognosis. Univariate analysis showed that early gestational week at diagnosis was the only feature significantly associated with poor prognosis. Thus, polyhydramnios, 'replaced' kidney and early gestational week at diagnosis, may indicate poor prognosis, to which obstetricians should pay attention.

Congenital Mesoblastic Nephroma Mimic Wilms Tumor on 18 F-FDG PET/CT and PET/MR.

ABSTRACT: Congenital mesoblastic nephroma is an extremely rare, low-grade malignant renal tumor in children. A 10-month-old boy and a 4-month-old girl were admitted to our hospital with a huge abdominal mass. For staging of the mass, 18 F-FDG PET/CT and PET/MR were performed showing a huge heterogeneous abdominal mass accompanied by extensive heterogeneous aggregation. Both of them were highly suspected to be Wilms tumor, the most common renal malignant tumor in children. However, histopathological examination after surgery confirmed congenital mesodermal nephroma.

Prenatal diagnosis of congenital mesoblastic nephroma.

A case of prenatal diagnosis of congenital mesoblastic nephroma by magnetic resonance is described.

Prenatal sonographic diagnosis of multicystic congenital mesoblastic nephroma.

The authors report an unusual presentation of congenital mesoblastic nephroma as a multilocular cystic renal lesion. Prenatal sonography revealed a unilateral, encapsulated, multilocular cystic mass with solid components measuring 5.7 × 5.4 × 4.3 cm in the left renal fossa. There was no increase in vascularity and no signs of hydrops fetalis. On the forth postnatal day left-sided radical nephrectomy was performed and histopathological examination revealed cellular type congenital mesoblastic nephroma. A multicystic appearance is rare as the vast majority of prenatally diagnosed congenital mesoblastic nephroma cases presented in the literature are of the classic type with solid homogenous or heterogenous appearence.

Papers presented at the fall 2020 Pediatric Urologic Oncology Work Group of the Societies of Pediatric Urology meetingPrenatally Diagnosed Solid Renal Mass.

Congenital mesoblastic nephroma is the most common renal neoplasm diagnosed in the first month of life of which 15% occur prenatally. We present a prenatal diagnosis of a 5.8 cm solid renal mass identified on the 36-week ultrasound. Labor was induced at 38 weeks and a female infant was delivered vaginally without complications. The postnatal ultrasound demonstrated a 6.3 cm heterogeneous mass nearly replacing the kidney. The infant underwent a radical nephrectomy on the first day of life and pathology confirmed stage II classic CMN with negative margins and nodes. She is otherwise healthy at follow-up of 1 year with no evidence of recurrence.

Imaging manifestations of congenital mesoblastic nephroma.

OBJECTIVE: Congenital mesoblastic nephroma (CMN) is a rare renal tumor mainly observed in infants and young children. This study aims to analyze the imaging manifestations of CMN to improve the understanding of the disease. METHODS: The imaging manifestations and clinical records of all pediatric patients with CMN admitted to our hospital over the last 7 years were retrospectively analyzed. The diagnosis of CMN was confirmed by postoperative pathology. All patients underwent computed tomography (CT) scans; 2 patients additionally underwent magnetic resonance imaging (MRI) scans (including one prenatal MRI scan). RESULTS: We evaluated 10 pediatric patients (6 males and 4 females) aged 7 days to 12 months (median age: 4 months) with CMN located on the left kidney in six cases and the right kidney in four cases. The CT imaging manifested as solid lesions (5 cases), solid-cystic lesions with solid predominance (4 cases), or solid-multicystic lesions with cystic predominance (1 case). Enhanced CT showed moderately and heterogeneously enhanced solid component and intracystic septations at the corticomedullary phase that were further enhanced at the nephrographic phase, although their CT values were still lower than those of the renal parenchyma. The "double-layer sign" were seen in 4 cases of classic type of CMN, and the "intratumor pelvis sign" were seen in 9 cases that include 5 classic, 3 cellular and 1 mixed type of CMN. In the 2 patients who underwent MRI, the scans showed solitary masses. The lesions had hypointense signals on the T1WI sequence and isointensity or slightly lower-intensity signals than the surrounding renal parenchyma on the fluid-sensitive sequences, whereas the lesions showed hyperintense signals on the diffusion-weighted imaging (DWI) sequence. CONCLUSIONS: The imaging manifestations of CMN are closely correlated with the pathological subtype and have certain characteristics. The "double-layer sign" was seen with most classic type CMN, and "intratumor pelvis sign" was seen in 90% cases.

Prenatal diagnosis of fetal congenital mesoblastic nephroma by ultrasonography combined with MR imaging: A case report and literature review.

RATIONALE: Fetal congenital mesoblastic nephroma (CMN) is a rare renal tumor, characterized by polyhydramnios, premature birth, and neonatal hypertension. In the prenatal stage, it is particularly difficult to diagnose CMN either by ultrasonography or magnetic resonance imaging (MRI). Thus, CMN is frequently detected in the third trimester in the clinical scenario. PATIENT CONCERNS: A 29-year-old G2P0 pregnant woman took routine prenatal examinations in our hospital. The fetal right kidney abnormality was not observed after 2 systematical ultrasonic examinations (at 24 and 31 weeks of gestation respectively), and only an increase was noticed in the amniotic fluid index (from 19.3 to 20.8 cm). DIAGNOSIS: CMN was detected by antenatal ultrasonography and MRI as a fetal right renal mass at 35 weeks of gestation in our hospital. INTERVENTIONS: The pregnant woman was admitted at a gestational age of 38 weeks and 5 days due to alterations in renal function. Further, the pregnant woman was administered with "oxytocin" to promote delivery, and the neonate underwent a right nephrectomy on the 9th day after birth. OUTCOMES: The pathological examination confirmed a cellular type of right CMN. The neonate recovered well after operation without adjuvant treatment. During 6 months of follow-up, the neonate grew well and showed no signs of recurrence or metastasis. CONCLUSION: Polyhydramnios detected during prenatal examination required attention due to the risk of malformation of fetal urinary system. Prenatal ultrasonography combined with MRI could not only clearly identify the origin of the tumor, but also distinguish the correlation between the tumor and adjacent structures, thereby leading to early diagnosis and favorable prognosis.

Contribution of magnetic resonance imaging to prenatal differential diagnosis of renal tumors: report of two cases and review of the literature.

Enlargement of a kidney on prenatal imaging is usually due to hydronephrosis or cystic renal disease, and much less often results from solid tumors such as mesoblastic nephroma, Wilms' tumor, nephroblastomatosis, renal sarcoma, and angiomyolipoma. All can be diagnosed by ultrasound. Magnetic resonance imaging is useful not only in confirming the presence of a renal mass, but also in the evaluation of the contralateral kidney for subtle abnormalities. We present one case each of Wilms' tumor and mesoblastic nephroma, both detected on antenatal ultrasound and further studied with fetal magnetic resonance imaging.

Cellular mesoblastic nephroma (infantile renal fibrosarcoma): institutional review of the clinical, diagnostic imaging, and pathologic features of a distinctive neoplasm of infancy.

BACKGROUND: Cellular mesoblastic nephroma has been associated with a more aggressive course than classic mesoblastic nephroma, including local recurrences and metastases. OBJECTIVE: To define the clinicopathologic and imaging features distinguishing cellular from classic mesoblastic nephroma. MATERIALS AND METHODS: Retrospective review of clinical charts and imaging studies of ten children with mesoblastic nephroma from 1996 to 2007 at a large children's hospital. RESULTS: In six children the mesoblastic nephroma was pure cellular, in two mixed, and in two classic. The mean ages at diagnosis were 107 days for those with the cellular form, and 32 days for those with the classic form. Hypoechoic or low-attenuation regions representing necrosis or hemorrhage were found in all children with the cellular form and in none of those with the classic form. Hypertension was present in 70% and hypercalcemia in 20% of the children and resolved following nephrectomy. Two cellular tumors encased major abdominal vessels. Local recurrence and metastases occurred within 6 months of tumor resection in two children with the cellular form. Intraspinal extension and intratumoral pseudoaneurysm were seen in one child with the cellular form. The cellular tumors shared histopathologic features with infantile fibrosarcoma (IFS), and RT-PCR testing in two children with the cellular form revealed the t(12;15) ETV6-NTRK3 gene fusion common to IFS. CONCLUSION: Distinct from the classic form, cellular mesoblastic nephroma is more heterogeneous in appearance on imaging, tends to be larger and present later in infancy, and can exhibit aggressive behavior including vascular encasement and metastasis. Intraspinal extension and intratumoral pseudoaneurysm are previously unreported findings encountered in our cellular mesoblastic nephroma series. The shared histopathology and translocation gene fusion support the concept of cellular mesoblastic nephroma as the renal form of IFS.

[Management of antenatal fetal abdominal tumors. Clues for the diagnosis of a congenital mesoblastic nephroma]. / Conduite à tenir obstétricopédiatrique devant la découverte anténatale d'une masse hyperéchogène rétropéritonéale. Arguments en faveur d'un néphrome mésoblastique congénital.

The prenatal diagnosis of abdominal mass poses the problem of its origin. Renal tumors are rarer than neuroblastoma but they are most often congenital mesoblastic nephroma. The congenital mesoblastic nephroma has a good forecast in spite of a sonographic impressive aspect. MRI can help to locate tumor but cannot tell difference between the different kinds of renal tumor. Prenatal forecast is especially linked with hydramnios and hydrops fetalis. Histolological study of the tumor is important for the prognosis. Two morphological subtypes are currently distinguished: the classic type with a good forecast and the atypical or cellular type. Distant metastases have been related only to the cellular form but especially in infants aged more than 3 months and never in the newborns. The diagnosis of the tumor does not change the mode of delivery except in case of an important volume. Complications are searched during the first days of life: hypertension, hypercalcemia, vomiting, hyperreninemia. Radical nephrectomy is performed after the end of the first week. In case of a classic form, the healing is always obtained. In case of cellular form, distant metastases are searched. In any rate, the follow-up is recommended until the end of the growth.

Prenatal diagnosis of congenital mesoblastic nephroma: a case with poor prognosis.

Congenital mesoblastic nephromais a rare tumour found in neonates, with a very small number of cases diagnosed prenatally. We report a case of a fetal renal tumour suspected at 28 weeks' gestation on routine ultrasound. Prenatal follow-up revealed a severe polyhydramnios at 32 weeks' gestation subsequent amniodrainage was undertaken. She delivered at 34+5 weeks' gestation, after spontaneous premature rupture of membranes.

Sonographic diagnosis of an unusual case of multilocular cystic nephroma mimicking polycystic kidney disease.

The following is a report of the unusual case of a multilocular cystic nephroma in an 8-year-old boy who was transferred to our unit with a palpable abdominal tumor. The patient suffered from thoracic pain and night sweating. The laboratory values were normal. Abdominal sonography showed a huge kidney tumor on the right side consisting of numerous small cysts transversed by irregular septa of variable thickness. The cysts had a diameter of 1 -5 mm; larger cysts of more than 1 cm in diameter were not able to be shown. In the center of the tumor a normal renal parenchyma was able to be shown. The tumor arose like a mushroom from the kidney. Color Doppler sonography showed good vascularity of the normal renal parenchyma while the tumor had only a few internal vessels. The tumor was surgically removed. The histologic diagnosis was cystic nephroma. Unusual features of this tumor were the small size of the numerous cysts similar to polycystic kidney disease and the mushroom-like growth of the tumor.

Specific computed tomography imaging characteristics of congenital mesoblastic nephroma and correlation with ultrasound and pathology.

INTRODUCTION: Congenital mesoblastic nephroma (CMN) is a common solid renal tumor in the neonate. Congenital mesoblastic nephroma can be divided into classic, cellular, and mixed types. The prognosis of CMN is very optimistic. But CMN can easily be misdiagnosed as the other malignant renal tumors by radiology. However, no studies have described the computed tomography (CT) imaging appearance of CNM in detail. The objective of this study is retrospective analyses of the multislice CT characteristics of CMN and their corresponding ultrasound findings and pathology. METHODS: This retrospective study reviewed the enhanced CT images of the CMNs and other renal tumors in children younger than 1 year in the past 10 years from the First Affiliated Hospital of Sun Yat-sen University. Two radiologists had noted the CT imaging characteristics of these images. t-test and Fisher's exact test were used in the comparison of imaging characteristics between the CMNs and other renal tumors. RESULTS AND DISCUSSION: Compared with other malignant renal tumors, the CMNs tend to appear as smaller round masses without clear coverage or clear boundary with the kidney in CT images (P < 0.01). The intratumor pelvis and the double-layer sign are the specific characteristics of CMNs (P < 0.01). The gender, quality of tumor (solid or solid-cystic), character of enhancement (homogeneous or heterogeneous enhancement), peri-renal hemorrhage, or peripheral lymph node enlargement showed no statistical significance (P > 0.05) between CMNs and other renal tumors. The appearances of CMN with classic components in the CT images are relevant to the pathological findings. The intratumor pelvis is caused by the classic components of CMN growing to encapsulate the pelvis. The double-layer sign in CT image correlates with the specific hypoechoic ring in ultrasound, which is caused by the slow blood flow and delay contrast agent filling in the blood sinus located in the peripheral part of the tumor. The differential diagnosis of CMN should include the other solitary renal tumors such as Wilms' tumor, clear-cell sarcoma of the kidney, and rhabdoid tumor of the kidney. CONCLUSION: The unclear coverage and unclear boundary with the kidney, the intratumor pelvis, and double-layer sign after contrast were specific CT imaging characteristics of CMN.

Congenital Mesoblastic Nephroma Presenting with Hematuria in a Neonate.

Congenital mesoblastic nephroma (CMN) is a rare tumor of infancy. CMNs can be histologically divided into classic, cellular, and mixed subtypes. Cellular CMNs are difficult to differentiate from Wilms tumors. Herein, a neonate with cellular CMN accompanied by macroscopic hematuria, is described. The clinical, pathological, and imaging features of the disease are discussed.

Management of mixed type congenital mesoblastic nephroma: Case series and review of the literature.

Congenital mesoblastic nephroma (CMN) is the most common renal tumor of infancy; however, it occurs infrequently with an incidence of 1 : 125,000. The cellular and classical variants are the most common subtypes of tumors, with a mixed variant occurring infrequently. We describe two cases of mixed variant CMN, which presented within days of each other differing in their clinical behavior. The first case followed a typical course, previously described in the literature, while the other deviated significantly. Traditionally, CMN presents as large abdominal mass in the neonatal period associated with a paraneoplastic syndrome, which can result in hypertension or hypercalcemia. Surgical resection is curative in most cases and long-term prognosis is excellent. Hypertension rarely persists after removal of the tumor, but remained in one of our two patients.