Therapy and outcome in 51 children with mesoblastic nephroma: a report of the National Wilms' Tumor Study

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 and postnatal management of congenital mesoblastic nephroma: A case report and literature review

BACKGROUND

Congenital mesoblastic nephroma (CMN) is a rare renal tumour in children, the most common kidney tumour in the neonatal period. It can be divided into three types, classical, cellular and mixed.

CASE PRESENTATION

A 31-year-old Chinese woman had no apparent foetal abnormality in regular prenatal care during the first and second trimesters. At 33 weeks of gestation, a solid mass in the right kidney was noted with echoes similar to liver and hypervascularity. It grew larger during late pregnancy. The infant was transferred to have a radical nephrectomy on the 9th day after birth. The postoperative histopathological result indicated classical CMN.

CONCLUSION

CMN could be detected prenatally, mainly during late pregnancy. The postnatal outcome is good.

Benign Renal Tumors in Pediatric Age Group: Retrospective Analysis

Background:

Benign renal tumors are extremely rare and were studied here. This series also includes a renal teratoma in a horseshoe kidney, probably only the second in the pediatric literature.

Materials and Methods:

Retrospective review of children with benign renal tumors operated between 2006 and 2018 at one center.

Results:

Twelve patients (M:F ratio 10:2), age range 3 weeks (31-week gestation) to 13 years presented with large palpable renal swelling (n = 12) and hematuria (n = 3). Computed tomography (CT) scan showed features typical of the tumor. Final histopathology (age group [mean]) showed: multilocular cystic nephroma (MLCN) - n = 5 (41.7%), (11–16 months [13.6]); congenital mesoblastic nephroma (CMN) - n = 4 (33.3%) (classic 1, cellular 3) (0.75–5 months [2.125]); mature cystic teratoma - n = 1 (8.3%): (48 months, in a horseshoe kidney), and angiomyolipoma (AML) - n = 2 (16.7%) (144 months [sporadic] and 156 months [tuberous sclerosis]) One patient with cystic teratoma with no calcification on CT scan received pre-operative chemotherapy as fine-needle aspiration cytology (FNAC) reported malignant small blue cell tumor. Nephroureterectomy with Gerota's fascia could be done easily in all without intraoperative complications. Delay in presentation in MLCN and CMN led to increased symptoms and CT scan changes. All patients did well in 1.5–12 years (median 3 years) follow-up including cellular mesoblastic nephroma.

Conclusions:

Benign renal tumors often occur in specific age groups but may overlap that of Wilms tumor. Proper interpretation of clinical presentation, CT scan, and FNAC findings help in avoiding preoperative chemotherapy. Upfront nephroureterectomy is curative. Histopathological findings decide further treatment. Children with AML and tuberous sclerosis need lifelong follow-up.

Many faces of Wilms Tumor: Recent advances and future directions

Background

Wilms’ tumor (WT) is the most frequently occurring paediatric renal tumor and is one of the most treatment-responsive tumors. A tumor-suppressor gene and other genetic abnormalities have been implicated in its etiology. In addition, patients with many congenital anomalies, such as Beckwith-Wiedemann syndrome, WAGR syndrome and Denys-Drash syndrome, have an increased risk of WT.

Methods and results

Two large collaborative groups – National Wilms Tumor Study Group (NWTSG)/Children's Oncology Group (COG) and The International Society of Paediatric Oncology (SIOP) have laid down the guidelines for standardized treatment of WT, though differing in the diagnostic and therapeutic approach. The major difference in the two guidelines is the timing of surgery: SIOP recommends using preoperative chemotherapy and NWTSG/COG prefers primary surgery before any adjuvant treatments. Both these groups currently aim at intensifying treatment for patients with poor prognosticators while appropriating the therapy to reduce long-term complications for those with favourable prognostic features. As the survival rate has now reached 90%, the primary objectives of the physician are to perform nephron-sparing surgery in selected cases and to reduce the dosage and duration of chemotherapy and radiotherapy in appropriate cases. The purpose of this review is to present current standards of diagnosis and treatment of WT around the world.

Conclusion

Further studies in future should be done to highlight the use of chemotherapy and radiotherapy under risk-stratified strategies. Further improvement in survival of these children can only be achieved by increasing awareness, early recognition, appropriate referral, and a multidisciplinary approach.

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o Most of the patients with WT have good prognosis.

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o Multimodality treatment and multidisciplinary care are the major contributors for an improved prognosis.

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o Further studies should be done on usage of chemotherapy and radiotherapy under more accurate risk-stratified strategies and to decrease the late effects of surgery.

Neonatal Renal Tumors

Renal tumors are rare in the neonatal period. Although some may be detected prenatally, a greater proportion present after birth, most often with a palpable abdominal mass with or without other associated symptoms. Cross-sectional imaging is typically followed by radical nephrectomy to make a specific histologic diagnosis to determine the need for additional therapy. This article reviews the clinical presentation, workup, treatment, and outcomes for neonates with some of the more common renal tumors seen in this population.

Unusual Case of Concurrent Retroperitoneal Congenital Infantile Fibrosarcoma and Cellular Type Congenital Mesoblastic Nephroma

BACKGROUND

Although congenital infantile fibrosarcoma (cIFS) is a rare soft tissue sarcoma among children, it constitutes one of the most common soft tissue sarcomas during the first year of life. Congenital mesoblastic nephroma (CMN) is the most common benign renal tumor usually developing during the first 3 months of life. cIFS and cellular type CMN (cCMN) share not only similar histopathologic features but identical molecular genetic abnormality including the ETV6/NTRK3 fusion gene. Here, we report an unusual case of cIFS occurring with cCMN.

CASE PRESENTATION

An 18-month-old girl presented with a 1-month history of abdominal distension and a few days' history of a palpable abdominal mass. A large heterogenous mass sized 9.0×11.2×11.6 cm on the right side of the abdomen and an isolated heterogenous lesion sized 4×4.5 cm within the right kidney were noted from the imaging study. Pathologic findings were consistent with cIFS and cCMN of the right kidney. In addition, both pathologic specimens contained the ETV6/NTRK3 fusion gene.

CONCLUSION

Although cIFS and cCMN share similar histopathologic features and molecular genetic abnormality, simultaneous occurrence of these 2 types of tumor is exceedingly rare. To our knowledge, this is the first unusual case report of concurrent cIFS and cCMN.

Laparoscopic management of congenital mesoblastic nephroma- case report

Congenital mesoblastic nephroma (CMN) also called leimyomatous harmartoma is a mesenchymal renal tumor. CMN is the most common solid tumor in newborns and young infants which is basically benign. Pathologically there are three variants of CMN - classic (conventional), cellular (which is more aggressive) and mixed. In a complete surgical removal of the tumor (nephrectomy), the literature results are excellent.

Ossifying Renal Tumor of Infancy: Laparoscopic Treatment and Literature Review

We present an unusual case of a rare ossifying renal tumor of infancy. A 6-month-old male initially presented with gross hematuria and without any palpable abdominal mass. Renal ultrasound and MRI showed a right lower pole, calcified, endophytic renal mass. Laparoscopic radical nephrectomy was performed without complications. Pathology demonstrated an ossifying renal tumor of infancy. We report this case, in addition to a review of the literature for similar cases, to highlight a rare renal tumor in infancy that can be managed laparoscopically.

Recurrent and metastatic congenital mesoblastic nephroma: where does the evidence stand?

PURPOSE

Fifty years ago, Bolande described Congenital Mesoblastic Nephroma (CMN) as a benign lesion. Unexpected aggressive clinical behaviors prompted a sub-classification based on histology. Recent molecular genetic evidence has identified the aggressive cellular variant to be the renal manifestation of congenital infantile fibrosarcoma. We submit a reappraisal and analysis of the available literature on recurrent and metastatic CMN.

METHODS

An electronic search of PubMed, MEDLINE, EMBASE, and Scopus yielded 38 children with local recurrence and/or metastases.

RESULTS

Of the 38 children with local recurrence and/or metastasis, 59% were girls. Median time to recurrence was 6 months (range 1-12 months). The commonest sites of metastases were the lung (39%) and liver (29%). Fifty percent of these children died of disease. The outcome of additional chemotherapy (p = 0.5) did not differ from that of surgery alone. The choice of chemotherapy did not influence the outcome (p = 0.6).

CONCLUSIONS

Recurrence and metastasis in cellular CMN are much more common than described earlier and carry a high mortality. Children with cellular and mixed CMN require close clinical and radiological follow-up for a minimum of 12 months after primary surgery. Surgery is the mainstay of the treatment of recurrent and metastatic lesions. Neoadjuvant chemotherapy is recommended only if the lesion is inoperable. Targeted therapy may be an option in treatment of refractory cases.

Congenital mesoblastic nephroma 50 years after its recognition: A narrative review

Congenital mesoblastic nephroma (CMN) is a rare pediatric renal tumor with low malignant potential that most commonly occurs early in infancy. Treatment strategies are based on the few published CMN series, while a significant number of CMN patients have been described in case reports. The aim of this narrative review was to create an up-to-date overview of the literature. Complete surgical removal is curative in most cases. The risk of treatment-related mortality (both surgery- and chemotherapy-related) is relatively high in the first weeks of life, indicating that these young patients deserve special attention with respect to timing and type of treatment.

Renal Tumors in Children Younger Than 12 Months of Age: A 65-Year Single Institution Review

Wilms tumor (WT) is the most prevalent pediatric renal tumor and most commonly occurs between ages 1 and 5 years. Data are lacking on children younger than 12 months with renal tumors. The cancer registry at the authors' institution was queried to identify patients 12 months and younger with renal masses. Demographics, clinical presentation, histopathology, stage, and survival outcomes were reviewed. The most common presenting symptoms included an asymptomatic abdominal mass (73%) and hematuria (9%). Histopathology revealed WT in 73% of patients, mesoblastic nephroma in 20%. Of those infants younger than 1 month of age, mesoblastic nephroma was the most common histopathology (68%). The 5-year overall survival (OS) was 93%, and 5-year event-free survival (EFS) was 93% for the entire group. For patients with WT, 5-year OS was 88% and 5-year EFS was 83%. Outcomes for congenital mesoblastic nephroma were excellent with 5-year OS and EFS of 100%. Reasons for good prognosis may be multifactorial and may include frequent well child checks in the first year of life and favorable histology. Patients in this age group are more likely to be classified as very low risk and may be treated with surgical resection alone.

Antenatally detected solid tumour of kidney

Congenital renal tumours are rare and usually benign. Polyhydramnios is the most common mode of presentation. Although most cases have been diagnosed postnatally, with advances in imaging technology, an increasing number of cases are being detected on antenatal scans. We describe a case of solid tumour of kidney detected in the second trimester of pregnancy and managed by surgery in the postnatal period.

Perinatal management of infant tumors and the promise of fetal surgery

PURPOSE OF REVIEW

This review outlines the current approaches to prenatal imaging, differential diagnosis, antenatal natural history, and the available treatment options for the most commonly prenatally diagnosed malignant tumors.

RECENT FINDINGS

In-utero diagnosis of fetal tumors, although still a rare event, has become more common as prenatal imaging modalities have improved. In general, this prenatal diagnosis allows more informed prenatal counseling and better perinatal planning for potentially high-risk deliveries. There are rare indications for prenatal fetal intervention.

SUMMARY

Diagnosis of a fetal tumor should prompt referral to a specialized center. Further understanding of these rare patients will require multicenter collaboration.

Pediatric non-Wilms' renal tumors: a third world experience

BACKGROUND

Pediatric non-Wilms' renal tumors (NWRT) are poorly understood owing to their heterogeneity and relative rarity. This study aimed at auditing the outcome of the management of NWRT in a tertiary hospital in the Third World.

METHODS

Records of all patients (n = 68) treated for NWRT over a 32-year period (1978-2010) were reviewed retrospectively.

RESULTS

The major histological groups included clear cell sarcoma of the kidney (CCSK) (33.8%), mesoblastic nephroma (17.6%), cystic partially differentiated nephroblastoma (CPDN) (17.6%), intrarenal neuroblastoma (8.8%), malignant rhabdoid tumor (MRT) (7.4%), and renal cell carcinoma (RCC) (5.9%). Sixteen (69.7%) patients with CCSK and 11 (91.7%) with CPDN were aged 1-4 years. Ten (83.3%) patients with mesoblastic nephroma were aged <1 year and three (60.0%) with RCC were aged 10-14 years. Ten (43.5%) patients with CCSK and four (80.0%) with RCC had metastases at diagnosis. The sensitivity of a pretreatment Tru-Cut biopsy was 100% for MRT. All the patients with CCSK, mesoblastic nephroma, CPDN, and RCC had radical nephrectomy. Only eight (34.8%) patients with CCSK received radiotherapy. The overall 1-10-year survival rates were 52.2%, 91.7%, 75.0%, 40.0% and 0.0% for CCSK, mesoblastic nephroma, CPDN, RCC, and MRT, respectively. The overall 1-10-year survival for the entire cohort was 51.5%.

CONCLUSIONS

The demography and clinical presentation of pediatric NWRT, which comprises 13.6% of pediatric renal tumors in the Third World, were similar to those in the Developed World. The overall 1-10-year survival for pediatric NWRT was low.

Mesoblastic nephroma: a report of the United Kingdom Children's Cancer and Leukaemia Group (CCLG)

BACKGROUND

Mesoblastic nephroma (MN) is a rare tumour which occurs mainly in early infancy and for which primary nephrectomy is the treatment of choice. This study aimed to assess surgical complications and outcomes in this patient group and to re-evaluate the age threshold of 6 months for recommending primary nephrectomy.

PROCEDURE

A retrospective file review of all cases of MN registered in UK Children's Cancer and Leukaemia Group renal tumour trials between October 1991 and March 2008. Data from the trials were compared with data held by the National Registry of Childhood Tumours, Oxford.

RESULTS

Forty-seven (3.5%) confirmed cases of MN were found among 1346 registered renal tumours. Median age at diagnosis was 30 days (range birth-3.8 years). MN was significantly more common in the first 3 months of life compared to between 3 and 6 months (33 vs. 2 cases). Seven cases occurred between 6 months and 1 year and only five cases occurred beyond 1 year of age. There was a significant difference in the age of diagnosis by histological subtype. There were 11 complications in the series; no registered patient developed a recurrent tumour; and all were alive at last follow-up.

CONCLUSIONS

Outcome for children with MN is excellent at all ages, with little indication for adjuvant chemotherapy. Children presenting at <3 months of age, should be treated by primary nephrectomy. In those presenting aged >3 months, alternative diagnoses should be considered, especially in the presence of surgical risk factors.

Regression of a congenital mesoblastic nephroma

Histologically, the cellular variant of congenital mesoblastic nephroma (CMN) is very similar to another rare tumor of infancy, infantile fibrosarcoma (IFS). In addition to the histologic similarities, these tumor types share cytogenetic abnormalities including translocation t(12;15)(p13;q25). We describe herein the case of a child who did not have immediate surgical resection of a CMN and whose tumor was untreated for 8 months. During that time, the tumor demonstrated a significant degree of regression. The shared translocation with IFS, a tumor with well-documented potential for spontaneous regression, suggests that this genetic abnormality may have contributed to the favorable clinical course.

Pediatric Renal Neoplasms

Renal tumors in childhood consist of a diverse group of tumors ranging from the most common Wilms' tumor, to the uncommon and often fatal rhabdoid tumor. Diagnosis is based on morphologic features and aided by ancillary techniques such as immunohistochemistry and cytogenetics. Molecular techniques have helped identify a group of pediatric renal cell carcinomas that have specific translocations, called translocation-associated carcinomas. Differential diagnosis of the various tumors is discussed. Pathogenesis and nephroblastomatosis, the precursor lesions of Wilms tumor, also are discussed briefly, as are the handling of these tumor specimens and prognostic factors.

WT1 expression and hemihypertrophy in congenital mesoblastic nephroma

Congenital mesoblastic nephroma (CMN) is a rare primary pediatric renal tumor occurring predominantly in infants. There is no known association between CMN and WT1 gene expression and the association of hemihypertrophy and CMN is not well known. We report an infant with isolated hemihypertrophy and WT1-positive CMN, and the results of WT1 immunostaining in 13 other patients with CMN diagnosed over 14 years at SickKids. Of the 14 total patients 3 had positive nuclear immunostaining for WT1. Two patients also expressed WT1 RNA by reverse transcription-polymerase chain reaction. In conclusion, contrary to previous reports, WT1 may be expressed in CMN and CMN can be associated with hemihypertrophy in the absence of Beckwith-Wiedemann syndrome.

Fetal and neonatal renal tumors

This is a review of renal tumors diagnosed between 1960 and 2007 in 47 fetuses and 163 infants less than 2 months old. There were 139 congenital mesoblastic nephromas, 41 Wilms' tumors, 23 rhabdoid tumors of the kidney, and 7 clear cell sarcomas of the kidney. The initial clinical manifestations, staging, management, and outcome of these patents are summarized in the tables and text.

Part II: Treatment of primary malignant non-Wilms' renal tumours in children

Renal-cell carcinoma, clear-cell sarcoma, (congenital) mesoblastic nephroma, rhabdoid tumour, and renal medullary carcinoma form a heterogeneous group of childhood renal malignancies known as non-Wilms' tumours. Progress has been slow in improving the management of these tumours to decrease morbidity and increase survival. However, greater cooperation between national and international centres should engender specialisation, and an increased knowledge of the molecular biology of these tumours will inevitably lead to substantial progress over the next decade. This review is the second of two parts: the first part provided an updated review of the clinical presentation, imaging, and pathology of non-Wilms' tumours and this second part provides an updated review of the treatment of these tumours.

Classification of malignant pediatric renal tumors by gene expression

BACKGROUND

The most common malignant renal tumors of childhood are Wilms tumor (WT), clear cell sarcoma of the kidney (CCSK), cellular mesoblastic nephroma (CMN), and rhabdoid tumor of the kidney (RTK). Because these tumors present significant diagnostic difficulties, the goal was to define diagnostically useful signatures based on gene expression.

PROCEDURES

Gene expression analysis using oligonucleotide arrays was performed on a training set of 47 tumors (10 CCSKs, 9 CMNs, 8 RTKs, and 20 WTs). Classifiers were developed for each tumor type using variations of compound covariate class predictor. The classifiers were applied to an independent test set of 72 tumors (3 CMN, 7 CCSK, 4 RTK, and 58 WT). Central review diagnosis was utilized as the gold standard. Correlation with the institutional diagnosis and qualitative estimation of confidence levels at the time of central review were noted.

RESULTS

Within the training set, classifiers resulted in no errors when >10 genes were utilized. Top genes in each classifier were verified using quantitative reverse transcription-polymerase chain reaction (RT-PCR). Applying the classifiers to the test set, 71 of 72 tumors were correctly classified with a confidence level of >99%. The exception was incorrectly classified by the gold standard. In comparison, by histopathology 31% of the non-WT were not accurately classified by the local institution, and 29% were classified with <95% confidence on central review.

CONCLUSIONS

Classifiers based on gene expression provide diagnostic confidence and accuracy greater than that of pathologic analysis alone. Tumors that show ambiguous gene expression profiles are those that are also pathologically and molecularly ambiguous and merit further analysis.

Mesoblastic nephroma—A report from the Gesellschaft fur Pädiatrische Onkologie und Hämatologie (GPOH)

BACKGROUND

Surgery alone is the appropriate first-line treatment for patients with mesoblastic nephroma (MN). Nevertheless, there are reports of local recurrences and metastasis, especially in the cellular subtype. The authors evaluated the outcome of patients with MN who were enrolled in either the International Society of Pediatric Oncology (SIOP) 93-01/GPOH or the SIOP 2001/GPOH Nephroblastoma Study and Trial.

METHODS

In total, 50 patients with MN were analyzed. Eleven patients were suspected antenatally of having a renal tumor. The median age at diagnosis was 18.5 days. Central pathologic review was performed for all specimens. The median observation time was 4.2 years.

RESULTS

Forty-five patients underwent initial surgery. Five patients older than 6 months received preoperative chemotherapy. Twenty-nine tumors were classic MN, and 21 tumors were cellular MN. Nine patients had a Stage III MN, 5 of those patients had tumor ruptures, and 8 had positive surgical margins. After they underwent nephrectomy, 40 patients received no further treatment. For the entire group, event-free survival (EFS) (94%) and overall survival (OS) (95%) were excellent. Patients with a cellular MN, patients with age 3 months or older, and patients with Stage III MN had lower EFS. Three patients developed recurrent disease, and 2 of those patients died. Metastases to the brain, lung, and liver were observed in 1 patient.

CONCLUSIONS

Radical nephrectomy with accurate surgical-pathologic staging is the standard of care for children with MN. Nonetheless, a subgroup of patients with MN (Stage III cellular MN in patients age 3 months or older) tends to develop recurrences more often. Further prospective studies will be needed to verify this finding and should help determine whether these patients may benefit from adjuvant therapy.

[Kidney tumors in childhood]

Types of renal tumors arising in children are different from those occurring in adults. Nephroblastoma is the most common (85%) with a clinical outcome which has dramatically improved in the last 30 years. Current classifications are aimed at better adaptation of treatment to each individual case, reducing iatrogenic complications without impairing total cure. Amongst entities which have been recently described or are better known we can find juvenile carcinoma associated with Xp11.2 translocation, renal medullary carcinoma, metanephric tumors, etc. Role of molecular cytogenetics is increasing for classification (and treatment) and this should always be kept in mind when dealing a fresh specimen of childhood renal tumor.

Prenatal diagnosis of congenital mesoblastic nephroma associated with renal hypertension in a premature child

In the present article, we report, for the first time, a prenatal diagnosis of a congenital mesoblastic nephroma in combination with a post-partum hyperreninemia with hypertension. A newborn was delivered at 35 weeks gestation who had an intrauterine diagnosis of a renal mass as early as 32 weeks gestational age by ultrasound examination. Tumor nephrectomy was performed on day 11 after delivery when an increase in hypertension was observed in the newborn.

Renal tumors in infants less than 6 months of age

BACKGROUND/PURPOSE

Renal tumors are rare in infants less than 6 months of age and may have associated paraneoplastic symptoms. To better define the characteristics of these tumors the authors reviewed their 10-year institutional experience.

METHODS

The authors searched the pathology database to identify all renal tumors resected at their institution since 1992 (after IRB approval and guidelines). The clinical presentation, operative details, pathology, and outcome for all children < or = 6 months of age were reviewed.

RESULTS

Of 101 children who had renal tumors resected during this period, 11 (11 %) were 6 months of age or less. Histopathologic examination showed congenital mesoblastic nephroma (CMN) in 7 patients (4 with cellular features), Wilms' tumor in 3 patients, and ossifying renal tumor of infancy in 1. Renal masses were detected antenatally in 2 patients and during newborn examination in 1 patient; however, the mean age at diagnosis was 72 +/- 18 days. Ten children had a palpable abdominal mass, 3 had gross hematuria, and 6 had hypertension (4 CMN; 2 Wilms'). Only 1 child had hypercalcemia (cellular CMN). Ten infants had nephroureterectomy, and 1 had a partial nephrectomy. All patients had either stage I or II disease. At follow-up (mean 4.2 +/- 1.2 years) 10 patients are alive with no evidence of disease. One newborn with hydrops and a very large congenital Wilms' tumor had abdominal compartment syndrome and died during surgery.

CONCLUSIONS

About 10% of renal masses may occur in infants less than 6 months of age. Although mesoblastic nephroma is the most common renal tumor in this age group, Wilms' tumor also may be seen. Paraneoplastic syndromes, such as hypertension and hypercalcemia, are common in these infants and are not specific for tumor type. These tumors generally present at an early stage and have an excellent prognosis overall.

Recent advances in pediatric renal neoplasia

Over the past 6 years, molecular genetic studies have significantly advanced our understanding of pediatric renal neoplasms. The cellular variant of congenital mesoblastic nephroma (but not the classic variant) has been shown to bear the same t(12;15)(p13;q25) and ETV6-NTRK3 gene fusion as infantile fibrosarcoma, a tumor with which it shares morphologic and clinical features. Rhabdoid tumor of the kidney is characterized by deletion of the hSNF5/INI1 gene, which links it to other rhabdoid tumors of infancy that arise in the soft tissue and brain. Primary renal synovial sarcomas and renal primitive neuroectodermal tumors have become accepted entities, and likely comprise a subset of what had previously been termed "adult Wilms tumor." Renal carcinomas associated with Xp11.2 translocations that result in fusions involving the TFE3 transcription factor gene have been delineated, including a distinctive neoplasm that shares the identical gene fusion as alveolar soft part sarcoma. Most recently, a distinctive type of renal neoplasm with a t(6;11)(p21;q12) has been described, and the cloning of the resulting gene fusion links it to the Xp11 translocation carcinomas. Together, these last two translocation-associated tumors represent a significant proportion of pediatric renal cell carcinomas. This review highlights each of these recent advances.

Use of sarcoma-based chemotherapy in a case of congenital mesoblastic nephroma with liver metastases

Congenital mesoblastic nephroma was originally considered to be a benign neoplasm. A more aggressive cellular form, however, that has a close relationship to congenital fibrosarcoma, is widely described. Previous reported sites of metastases are the lungs, heart, brain, and bone. We describe a patient with isolated metastasis to liver and review the management, together with evidence that it may be more appropriate to use a vincristine, ifosfamide, doxorubicin, and etoposide (VIDE) regimen rather than Wilm's tumor-based regimens in those cases for which chemotherapy is indicated.

Complete response of recurrent cellular congenital mesoblastic nephroma to chemotherapy

Congenital mesoblastic nephroma (CMN) is usually cured by surgery. The sensitivity of this tumor to chemotherapy is unknown. The recent description of a t(12;15)(p13;q25) chromosomal translocation in both cellular CMN and congenital infantile fibrosarcoma suggests that these entities have a common pathogenesis, and that cellular CMN might respond to chemotherapy like congenital infantile fibrosarcoma does. The authors describe three patients with recurrent cellular CMN who showed a complete response to chemotherapy. Based on these patients and a review of the literature, the authors suggest that chemotherapy be considered as a part of the therapy for recurrent or unresectable cellular CMN.

Prenatal detection of mesoblastic nephroma by sonography and magnetic resonance imaging

Congenital mesoblastic nephroma is the most common neonatal kidney tumor and surgical excision is almost always curative. We report the prenatal detection of congenital mesoblastic nephroma by sonography and magnetic resonance imaging. After birth, a right nephrectomy was performed and the baby recovered well.

Non-Wilms' renal tumors in children

Renal tumors other than Wilms' tumors are infrequent in childhood. Wilms' tumors account for 6% to 7% of childhood cancer, whereas the remaining renal tumors account for less than 1%. The most common non-Wilms' tumors are clear cell sarcoma of the kidney, rhabdoid tumor of the kidney, renal cell carcinoma, mesoblastic nephroma, and multilocular cystic nephroma. Collectively, these tumors account for less than 10% of the primary renal neoplasms in childhood.

Hyperreninemia and congenital mesoblastic nephroma: case report and review of the literature

A 32-week estimated gestational age female infant had elevated systolic blood pressure at birth and a palpable left abdominal mass. Radiologic evaluation revealed a left upper pole renal mass. The renin level was significantly elevated. Left nephrectomy confirmed a diagnosis of congenital mesoblastic nephroma. The postoperative renin level normalized along with the blood pressure. Histologic analysis identified renin production from either the mesoblastic nephroma or secondarily from compression or ischemia. Mesoblastic nephroma should be considered as part of the differential diagnosis for hypertension in the young. The renin concentration and a renal ultrasound scan should be obtained as part of the evaluation.

Congenital mesoblastic nephroma: report of a Case with review of the most significant literature

AIMS AND BACKGROUND

Congenital mesoblastic nephroma (CMN) is a rare pediatric tumor of the kidney with the highest peak of incidence during the first 3 postnatal months. It has previously been confused with Wilms' tumor (which, on the contrary, is rare during the first six months of age and is still considered a histogenetic congener). CMN almost always has a favourable prognosis. Therefore, CMN needs to be correctly diagnosed and differentiated from other pediatric renal neoplasms. Two morphological subtypes are currently distinguished histologically: the classical or leiomyomatous type and the atypical or cellular type. Mixed forms with a combination of the two patterns are also on record. Recurrence and even tumor-related death have been described in the literature and always related to the atypical form or to the mixed form, particularly in patients aged more than 3 months and in those cases in which the surgical removal was not complete. Opinions concerning post-surgical clinical management, especially in regard to adjuvant therapy, are not unanimous.

METHODS

A case of CMN, predominantly of the classical histological subtype diagnosed in a baby with a follow-up of 6 years, is herein presented. The tumor was discovered at birth and surgically removed after one month. Since the tumor showed a high mitotic index (one of the characteristics of the cellular subtype) and the perirenal fat was focally involved with the tumor, the possibility of giving adjuvant chemotherapy was considered. Flow cytometric analysis was also performed which showed a diploid DNA content of neoplastic cells.

RESULTS

The tumor was completely removed, surgical margins were free histologically, and no clear-cut histological features of the atypical subtype were noted. Flow cytometrically, it showed the euploid DNA content. Consequently no additional therapy was given. Six years after surgery the patient is developing well and is free of disease. He has regular follow-up examinations.

CONCLUSIONS

CMN almost always pursues a benign clinical course if diagnosed under three months of age and if totally surgically excised independent of histological type. Criteria for management of atypical cases are not unanimous in regard to the benefit of additional therapy after surgery.

Pediatric renal tumors

A broad spectrum of renal tumors occurs in infants and children ranging from the benign cystic nephroma to the extremely aggressive malignant rhabdoid tumor of the kidney. A thorough understanding of these tumors is crucial to the optimal diagnosis and management of children with renal masses. The common renal tumors in infants and children are discussed and an orderly method for their evaluation is presented. Recent developments in the molecular biology of Wilms' tumor are outlined to provide insight into the origin of this tumor.

Congenital mesoblastic nephroma t(12;15) is associated with ETV6-NTRK3 gene fusion: cytogenetic and molecular relationship to congenital (infantile) fibrosarcoma

Morphological, cytogenetic, and biological evidence supports a relationship between congenital (infantile) fibrosarcoma (CFS) and congenital mesoblastic nephroma (CMN). These tumors have a very similar histological appearance, and they are both associated with polysomies for chromosomes 8, 11, 17, and 20. Recently, CFS was shown to contain a novel t(12; 15)(p13;q25) translocation resulting in ETV6-NTRK3 gene fusion. The aims of this study were to determine whether congenital mesoblastic nephroma contains the t(12;15)(p13;q25) translocation and ETV6-NTRK3 gene fusion and whether ETV6-NTRK3 fusions, in CMN and CFS, antedate acquisition of nonrandom chromosome polysomies. To address these aims, we evaluated 1) ETV6-NTRK3 fusion transcripts by reverse transcriptase polymerase chain reaction and sequence analysis, 2) genomic ETV6-region chromosomal rearrangement by fluorescence in situ hybridization, and 3) chromosomal polysomies by karyotyping and fluorescence in situ hybridization. We report ETV6-NTRK3 fusion transcripts and/or ETV6-region rearrangement in five of six CMNs and in five of five CFSs. The ETV6-NTRK3 fusion transcripts and/or ETV-region chromosome rearrangements were demonstrated in two CMNs and one CFS that lacked chromosome polysomies. These findings demonstrate that t(12;15) translocation, and the associated ETV6-NTRK3 fusion, can antedate acquisition of chromosome polysomies in CMN and CFS. CMN and CFS are pathogenetically related, and it is likely that they represent a single neoplastic entity, arising in either renal or soft tissue locations.

Adult mesoblastic nephroma: expansion of the morphologic spectrum and review of literature

Mesoblastic nephroma (MN) is a distinctive tumor that is seen mostly in early infancy and that consists of classic and cellular (atypical) variants. Mesoblastic nephroma rarely occurs in adulthood, but MN in this age group still is poorly characterized because there are only 17 reported cases. We describe five additional cases of adult MN, including one case of the cellular variant, characterize the immunohistochemical profiles in detail, and critically review the previously reported cases. The collective data obtained from these 22 cases of adult MN showed that the patients predominantly were women (20 cases), ranging in age from 19 to 78 years, who were asymptomatic (5 cases) or had nonspecific signs and symptoms referable to a renal mass. Twenty tumors were classified as classic and 2 as cellular. The tumors were 2-24 cm, well circumscribed, and partially encapsulated and displayed a solid/ cystic cut surface, with a predominantly solid component in most tumors. One tumor, however, was almost purely cystic. Most tumors extended to the renal sinus. and some appeared entirely intrapelvic on imaging studies; however, gross and microscopic evaluation did not show destructive invasion of the pelvic wall. Extension of the tumor beyond the renal capsule has not been described. Each tumor was composed of epithelial and stromal components both. The epithelial component, which displayed no difference between the classic and cellular variants, was composed of isolated or clustered tubules and cysts lined by a benign epithelium with a wide range of cytologic differentiation. The stromal cells were composed of fibroblasts, myofibroblasts, and smooth muscle cells in various combinations. Stromal cellularity was low for the classic variant but high for the cellular variant. Hemorrhage, necrosis, and high mitotic index were noted in the stroma of the cellular, but not in the classic variant. Immunohistochemical study applied to the five current cases and seven normal control kidneys confirmed the presence of fibroblasts, myofibroblasts, smooth muscle cells, and prominent vessels in the stroma of each tumor. Most cysts and tubules within the tumors had a distinctive immunohistochemical profile, similar to that of collecting duct but different from those of other portions of the nephron in the normal control kidneys. After total or partial nephrectomy, without adjuvant chemotherapy or radiotherapy, 19 patients, including the 2 with cellular MN, were alive and well at 8-months to 48-years follow-up. Follow-up was not available in two patients. The remaining patient had recurrence at the surgical site 24 years after nephrectomy. Adult MN displays a distinctive morphologic spectrum that parallels that of its pediatric congener. It probably is a benign tumor that can be treated successfully by complete excision. The collecting duct differentiation expressed by most tubules and cysts of adult MN implies ureteric bud, which is the exclusive embryologic origin of collecting duct, as an important element in the histogenesis of this rare but fascinating type of tumor.

Cytogenetic and molecular analysis of cellular atypical mesoblastic nephroma

Cytogenetic and molecular analyses were performed on three cellular (atypical) congenital mesoblastic nephromas (CMNs). Two cases had trisomy 11; in one, it was the sole karyotypic abnormality, and the other had additional numerical changes as well as an isochromosome for the long arm of chromosome 1. Markers for the 11p13 and 11p15 loci were present in three copies in these two CMNs. In the third CMN, two apparently normal copies of chromosome 11 were present together with additional numerical and structural chromosome changes. Because loss of heterozygosity was observed for both 11p13 and 11p15 markers, we assume that mitotic recombination occurred. Duplication and loss of imprinting of genes at 11p15 has also been observed frequently in Wilms' tumor. We therefore propose that CMN and Wilms' tumor might share common genetic pathways.

Renal neoplasms of childhood

Wilms' tumor is the most common childhood renal tumor. This article describes the epidemiology, histopathologic features, and clinical manifestations of Wilms' tumor along with the spectrum of imaging findings using different modalities. The distinguishing features of other renal tumors encountered in children, such as clear cell sarcoma, rhabdoid tumor, congenital mesoblastic nephroma, multilocular cystic renal tumor, renal cell carcinoma, and angiomyolipoma are also reviewed.