Congenital mesoblastic nephroma: a clinicoradiologic study of 17 cases representing the pathologic spectrum of the disease

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.

The Placenta as a Target for Alcohol During Pregnancy: The Close Relation with IGFs Signaling Pathway

Alcohol is one of the most consumed drugs in the world, even during pregnancy. Its use is a risk factor for developing adverse outcomes, e.g. fetal death, miscarriage, fetal growth restriction, and premature birth, also resulting in fetal alcohol spectrum disorders. Ethanol metabolism induces an oxidative environment that promotes the oxidation of lipids and proteins, triggers DNA damage, and advocates mitochondrial dysfunction, all of them leading to apoptosis and cellular injury. Several organs are altered due to this harmful behavior, the brain being one of the most affected. Throughout pregnancy, the human placenta is one of the most important organs for women's health and fetal development, as it secretes numerous hormones necessary for a suitable intrauterine environment. However, our understanding of the human placenta is very limited and even more restricted is the knowledge of the impact of toxic substances in its development and fetal growth. So, could ethanol consumption during this period have wounding effects in the placenta, compromising proper fetal organ development? Several studies have demonstrated that alcohol impairs various signaling cascades within G protein-coupled receptors and tyrosine kinase receptors, mainly through its action on insulin and insulin-like growth factor 1 (IGF-1) signaling pathway. This last cascade is involved in cell proliferation, migration, and differentiation and in placentation. This review tries to examine the current knowledge and gaps in our existing understanding of the ethanol effects in insulin/IGFs signaling pathway, which can explain the mechanism to elucidate the adverse actions of ethanol in the maternal-fetal interface of mammals.

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.

Pediatric Renal Neoplasms:: MR Imaging-Based Practical Diagnostic Approach

Pediatric renal tumors may be malignant or benign. Wilms tumor, the most common malignant pediatric renal tumor, arises sporadically or with various syndromes. Renal cell carcinoma typically presents in older children. Renal clear cell sarcoma and rhabdoid tumor are typically less common, more aggressive, and present in younger children. Benign renal tumors include mesoblastic nephroma, multilocular cystic renal tumor, angiomyolipoma, and metanephric adenoma. Lymphoma and leukemia may secondarily involve the kidney. Although there is overlap in the imaging appearance of several pediatric renal tumors, magnetic resonance characteristics and clinical data narrow the differential diagnosis and suggest a specific diagnosis. This article reviews current MR techniques, as well as the common MR imaging characteristics of malignant and benign pediatric renal neoplasms.

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.

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.

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.

Mixed subtype of congenital mesoblastic nephroma with poor evolution: a case report and literature review

A male child born at 27 weeks, weighting 1305 g and presenting with a right-sided abdominal tumor. Computed tomography scan demonstrated the presence of a solid mass compressing the right kidney. Puncture biopsy revealed congenital mesoblastic nephroma. The patient underwent total right nephroureterectomy, and died on the second day after surgery.

Cellular mesoblastic nephroma with liver metastasis in a neonate: prenatal and postnatal diffusion-weighted MR imaging

Congenital mesoblastic nephroma (CMN) is the most common renal tumor in the first year of life. Here, we present unique findings of cellular variant CMN seen on prenatal and postnatal MRI with diffusion-weighted imaging (DWI).The mass was well-visualized on prenatal MR DWI with diffusion restriction in the solid portions. After excision of the mass, follow-up whole body MRI with DWI helped identify local tumor recurrence with suspicious liver metastasis. This hepatic lesion also showed diffusion restriction.

Renal and hepatic tumors in the neonatal period

Renal and hepatic tumors in neonates are extremely rare. Nevertheless it is important for clinicians to be familiar with them. Both renal and hepatic neonatal tumors are heterogeneous collections of several tumor types. Some renal and hepatic tumors are benign and may require no interventions whereas others can be associated with significant morbidity and even mortality and may require multimodality treatment. Early diagnosis and initiation of the proper treatment plan is crucial for achieving the best outcomes for these rare tumors in this vulnerable population.

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.

Imaging of congenital mesoblastic nephroma with pathological correlation

BACKGROUND

There are a variety of imaging findings for congenital mesoblastic nephroma (CMN) and two main pathological variants: classic and cellular.

OBJECTIVE

To determine whether imaging findings in children can predict the likely pathological variant.

MATERIALS AND METHODS

We reviewed imaging in children with pathology-proven CMN. Imaging findings correlated with gross and histological appearance.

RESULTS

In 15 boys and 15 girls with CMN, US was performed in 27, CT in 19, and MRI in 7. Cystic components were readily identified on US; central hemorrhage was better differentiated on CT. MRI demonstrated high sensitivity for both. Histology confirmed classic CMN in 13 children, cellular CMN in 14 and "mixed" CMN in 3. Age at presentation was significantly higher in children with the cellular variant. Of 15 solid or predominantly solid tumors and 10 lesions with a hypoechoic ring, 12 and 7, respectively, had pathology consistent with classic CMN. In contrast, five of seven with intratumoral hemorrhage and all with a large cystic/necrotic component had pathology consistent with the cellular variant.

CONCLUSION

The imaging appearance of CMN is often determined by the pathological type of tumor. Findings suggestive of the classic variant include a peripheral hypoechoic ring or large solid component. In comparison, cystic/necrotic change and hemorrhage is much more common in cellular CMN.

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.

Imaging of the neonatal genito-urinary tract

OBJECTIVE

To describe imaging of typical conditions and diseases in the neonatal genito-urinary (GU) tract.

METHOD

The use, the applications, and typical findings using standard imaging techniques (e.g., ultrasound, US, voiding cystourethrography, VCUG) are described, with emphasis on technical aspects, indications, and restrictions in neonatal queries. Only basic applications as used in routine clinical work are included, other more sophisticated and advanced imaging techniques such as scintigraphy, MR-urography, genitography or image-guided interventional procedures will only briefly be mentioned.

SUMMARY AND CONCLUSION

Conventional imaging methods are valuable and - particularly in the neonatal GU tract - sometimes irreplaceable. Skillfully used basic imaging techniques, particularly of US (including modern methods such as Doppler sonography, Harmonic imaging or contrast enhanced US), supplemented by fluoroscopy for VCUG can answer most acutely treatment relevant queries. Rarely early scintigraphic studies, genitography, or MRI may become indicated, usually not for establishing the diagnosis, but to collect additional (functional or anatomical) information necessary for deciding on further treatment, or even image guided interventional procedures may become necessary.

Genitourinary imaging techniques

In the current era of pediatric uroradiology, use of nuclear medicine, ultrasonography, CT, and MRI has been valuable in the identification and management of genitourinary diseases. Excellent information about the renal parenchyma and renal function is currently attainable with current cross-sectional imaging techniques that can identify tissue differentiation of lesions, distinguish dilatation of the pelvocalyceal system, and determine margins of the kidney and perirenal space. Invasive angiography is limited in application specifically to vascular diseases, although they are uncommon in childhood. Because of these newer techniques, intravenous urography has lost its position as the "cornerstone" of urinary tract imaging and is used mainly to identify pathologic conditions of the ureters.

[Childhood kidney tumors -- the relevance of imaging]

Kidney tumors represent 6.2% of malignant tumors in children. History, clinical course and radiological findings are necessary elements in the differential diagnosis of the different renal tumors. In the case of nephroblastoma, chemotherapy is based solely on the radiological diagnosis without prior histology. In therapy-optimizing studies of the Society of Pediatric Oncology and Hematology, preoperative chemotherapy is performed. Therapy monitoring is performed in the course of and after preoperative chemotherapy to verify tumor response. Radiological staging plays a significant role in deciding on further treatment and in operative planning. Three-dimensional visualization of the abdominal situs can assist preoperative planning. In summary, diagnostic imaging in renal tumors in children plays a role in differential diagnosis, staging, monitoring of therapy, and surgical planning.

Nephron-sparing surgery in children with primary renal tumor: indications and results

Nephron-sparing surgery (NSS) is the treatment of choice for children with bilateral Wilms' tumor (WT), or with WT on a single kidney, or with WT and a disease of the contralateral kidney, or with benign kidney tumor. NSS is a reasonable alternative to nephrectomy in children at risk of metachronous WT, including children with genetic syndromes, children younger than 1 year of age, and children with hyperplastic nephroblastomatosis. The use of NSS in selected children with "low-risk" or stage I "intermediate-risk" WT and a normal contralateral kidney is still controversial. Available data suggest that, in children with WT, NSS does not impair the outcome and has a renal function advantage over nephrectomy.

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.

Imaging of renal tumours in infancy and childhood

There is a large range of benign and malignant renal neoplasms. This article lists the most benign, indeterminate and malignant renal tumours that occur during infancy and childhood. It briefly describes the most important entities, including their imaging features, and important complications. Differential diagnosis and pitfalls are discussed, and a brief suggestion for a standardised imaging algorithm is proposed. Although modern imaging techniques, including colour Doppler sonography, helical or multidetector CT, and MR have significantly improved imaging potential, the definite diagnosis on tumour entity still is established only by histology.

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.

From the archives of the AFIP. Infiltrative renal lesions: radiologic-pathologic correlation. Armed Forces Institute of Pathology

Most renal masses exhibit an expansile growth pattern characterized by radial tumor enlargement that displaces normal renal parenchyma and forms spherical, often exophytic, lesions. These expansile masses have pushing margins that impress adjacent normal renal parenchyma but do not infiltrate it; this behavior results in a well-defined, encapsulated appearance at both radiologic and gross pathologic examination. In contrast, certain disease processes involve the kidney in an infiltrative fashion by using the normal renal architecture as scaffolding for interstitial growth. These infiltrative renal lesions lack a sharp border of demarcation with the normal parenchyma and therefore demonstrate ill-defined zones of transition between the lesion and normal parenchyma. Although infiltrative lesions frequently enlarge the kidney, its reniform shape is usually maintained. Cross-sectional imaging can often help distinguish infiltrative from expansile growth patterns through analysis of the parenchymal interface between the process and the kidney, the effect of the lesion on the collecting system and renal sinus, and the overall renal morphology. A wide variety of neoplastic and inflammatory conditions characteristically involve the kidney by cellular infiltration. Although considerable overlap of the imaging features exists among the various infiltrative processes, the correct diagnosis may be suspected when the clinical data and associated radiologic findings are considered together.

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.

The role of imaging in renal and extra-renal rhabdoid tumours

Rhabdoid tumour of the kidney is an uncommon malignancy with a poor prognosis that usually occurs in childhood. Certain imaging features may help distinguish this lesion from the much more common Wilms' tumour. Extra-renal rhabdoid tumours appear to have no specific imaging characteristics.

Preoperative chemotherapy for mesoblastic nephroma

A neonate with extensive stage III mesoblastic nephroma was confirmed at operation to have a tumor that was too infiltrative and too advanced for primary excision. The abdomen was closed after multiple biopsies. Vincristine (1.1 mg/m2) was given intravenously once a week for a total of eight doses. Repeat CT scan confirmed shrinkage of the tumor and a nephrectomy could be performed safely and the tumor removed at the second laparotomy. CT scan repeated 1 year later showed no recurrence. This case illustrates the effective use of a single drug pre-excision chemotherapy which allowed a nephrectomy for extensive stage III mesoblastic nephroma to be carried out safely.

Presence or absence of trisomy 11 is correlated with histologic subtype in congenital mesoblastic nephroma

Fluorescence in situ hybridization utilizing a probe for the alpha satellite repeat sequence on chromosome 11 was used to detect variations in the number of chromosomes 11 in 24 formalin-fixed, paraffin-embedded congenital mesoblastic nephromas. Evidence of trisomy 11 was found in nearly half of the tumors. More importantly, the presence of trisomy 11 was associated with the cellular histologic variant of this tumor.

Congenital mesoblastic nephroma presenting with hemoperitoneum and shock

We describe an unusual presentation of a congenital mesoblastic nephroma in a 5-month-old boy. He was in hemodynamic shock in admission. Sonography revealed an echogenic right kidney and hemoperitoneum. Right nephrectomy was performed, and he is well one year later without any further treatment.

Congenital mesoblastic nephroma: cytogenetic comparison to leiomyoma

We report the karyotype analysis of a congenital mesoblastic nephroma (CMN), a usually benign renal tumor occurring most commonly during early infancy. The tumor was composed of interlacing bundles of spindle-shaped cells and it displayed both the classic and cellular histologic patterns. Immunoperoxidase studies showed reactivity for vimentin and actin. The tumor cell karyotype included additional chromosomes 11 and an altered chromosome 12. Trisomy or tetrasomy of chromosome 11 is present in five of six reported cases and may represent a frequent alteration in the karyotype of the CMN. Furthermore, breakpoints in the q13-15 region of chromosome 12 are commonly seen in leiomyomas, which are histologically similar to the CMN. Thus, the karyotype described here illustrates another similarity between the two tumor types.

A further diagnostic test in neonatal/infant solid renal mass: two cases of mesoblastic nephroma showing uptake of Tc99mDMSA

During the first 6 months of life, mesoblastic nephroma is the most common cause for a solid renal tumour. We describe two cases showing uptake of Tc99mDMSA by mesoblastic nephroma. Tc99mDMSA scanning may suggest the correct diagnosis and so allow nephrectomy without biopsy, rendering the latter unnecessary in mesoblastic nephroma.

Mesoblastic nephroma metastatic to the lungs and heart--another face of this peculiar lesion: case report and review of the literature

A case of mesoblastic nephroma in a 14-month-old girl who developed consecutive metastases in the lung and the heart is presented. This tumor is considered to be benign and cured by surgery only. Recurrent cases are extremely rare and usually related to unclear surgical margins. Metastatic mesoblastic nephroma has been previously described in only two cases. The present case highlights a new, previously undescribed feature--the ability to metastasize to sites other than lung.

Molecular characterization of congenital mesoblastic nephroma and its distinction from Wilms tumor

BACKGROUND

Congenital mesoblastic nephroma (CMN) is a rare tumor of the neonatal kidney. It was once thought to be a variant of Wilms tumor that also arises from primitive renal cells.

METHODS

Molecular characteristics of two CMN were studied to clarify their potential relationship to Wilms tumors. Patterns of gene expression were assayed by Northern blot hybridization analysis. Tumors were tested for loss of heterozygosity (LOH) at chromosomes 11p13 and 11p15 using Southern blot analysis.

RESULTS

The CMN, like Wilms tumors, demonstrated high-level expression of insulin-like growth factor II. Unlike Wilms tumors, however, the CMN expressed neither the N-myc oncogene nor the putative Wilms tumor suppressor gene, WT1. Using a panel of probes spanning 11p13 and 11p15, no LOH was detected in the CMN, nor was there evidence of deletion or rearrangements of WT1.

CONCLUSIONS

Although Wilms tumor and CMN both arise from the developing kidney, molecular characterization suggests that different factors are involved in the pathogenesis of these two tumors.

Preoperative chemotherapy of cellular congenital mesoblastic nephroma in a 5-month-old infant

Cellular (or atypical) congenital mesoblastic nephroma (CMN) is a potentially aggressive form of the benign classical congenital mesoblastic nephroma. We report here a case of cellular CMN in a 5-month-old boy treated preoperatively with chemotherapy with an excellent response allowing a complete surgical resection.

renal tumors and tumor-like lesions in pediatric patients

Renal enlargement presenting as an abdominal mass(es) is attended by a lengthly differential diagnosis of non-neoplastic and neoplastic lesions with a range in serious connotations and consequences. Simple compensatory hypertrophy and unilateral multicystic dysplasia are relatively innocuous and easily recognized with appropriate imaging studies; they are also related in the sense that the normal contralateral kidney hypertrophies in the absence of a non-functioning dysplastic kidney. Bilateral nephromegaly in a neonate is generally a sign of autosomal recessive polycystic kidney disease or multicystic dysplasia secondary to distal obstructive uropathy. Primary neoplasms of kidney in the pediatric population in the past were traditionally classified as Wilms' tumors, but that erroneous practice has been eliminated with the recognition of several distinctive neoplasms in addition to classic Wilms' tumor. Separating a typical Wilms' tumor from mesoblastic nephroma, clear cell sarcoma of the kidney and the malignant rhabdoid tumor, for treatment and prognostic purposes, has become the accepted norm in the past 12-13 years. Another important advance at the cellular level is the recognition of a deletion in the short arm of chromosome 11 in the cultured cells of Wilms' tumor and in the germ cell line in certain clinical settings of Wilms' tumors. A dramatic expansion in the understanding and management of childhood renal neoplasms has occurred through the multimodality approach of laboratory investigation and applied clinical research.

Congenital mesoblastic nephroma, nephrocalcinosis, and hypertrophic pyloric stenosis

A cellular variant of congenital mesoblastic nephroma (CMN) occurring in a newborn is presented. Coincidental findings were congenital hypertrophic pyloric stenosis (CHPS) and nephrocalcinotic hypercalcemia that reverted after nephrectomy. As of the day of writing, this multiple association has not been reported. The authors believe that both CMN and CHPS could be interpreted as fibroblastic proliferative-related entities. Transient hypercalcemia seems to be a paraneoplastic phenomenon.

Congenital mesoblastic nephroma: possible prognostic and management value of assessing DNA content

The case records and pathology of all children with kidney tumours treated in the West Midlands Health Authority Region (WMHAR) from 1957 to 1986 were reviewed. The histology was reviewed by a panel of three paediatric pathologists. Thirteen (6%) out of 211 cases were considered to have congenital mesoblastic nephroma (CMN). Nine were of the conventional type, three of the atypical cellular type, and one mixed. DNA ploidy was investigated and showed two of the tumours to be aneuploid and nine diploid (tissue was not available in the two other cases). The two aneuploid tumours were of atypical cellular and mixed histology, respectively; the diploid tumours were of the conventional type in eight cases and atypical cellular in one. The atypical cellular type has been reported to behave more aggressively, but the benefit of additional treatment after surgery to prevent recurrence remains unclear. Measurement of DNA content by flow cytometry, together with histological subclassification, may be useful in selecting patients who will benefit from further treatment after surgery.

Congenital mesoblastic nephroma occurring in a solitary kidney

Congenital mesoblastic nephroma (CMN) is a rare tumour arising in early infancy. This is the first reported case of CMN arising in a solitary kidney. The literature and radiological features of CMN are reviewed.

Cellular congenital mesoblastic nephroma: what are the options

Cellular congenital mesoblastic nephroma is a potentially aggressive variant of the usually benign congenital mesoblastic nephroma. Our recent experience with 3 patients with cellular congenital mesoblastic nephroma prompted a critical review of the literature to evaluate risk factors for recurrence and present treatment programs. A total of 38 patients, including our 3 patients, with cellular congenital mesoblastic nephroma were divided into 2 groups: those with recurrent (7) and those with nonrecurrent (31) tumors. A statistical comparison of clinical and pathological data was performed. Of the 7 patients with local recurrence and/or pulmonary metastasis, 3 died. The average time to first recurrence was 5.4 months. Histological differences were not predictive of recurrent disease. Pathologically positive surgical margins (p less than or equal to 0.02) were the only statistically significant variable suggesting recurrent disease. While the presenting age was not predictive of recurrence (p equals 0.27), the relative risk of recurrence doubles in the first 3 months of life and quadruples after 6 months of life. Treatment programs also were evaluated. An infant with cellular congenital mesoblastic nephroma, regardless of age, is cured with surgery alone given clear pathological margins. In 4 of 5 children with recurrent tumors Wilms tumor treatment agents (vincristine and actinomycin D) failed to control local or distant disease. Of these cases 2 subsequently were treated with sarcomatous chemotherapy (vincristine, cyclophosphamide and doxorubicin) and both are in remission. These agents may prove to be more efficacious in the treatment of local or metastatic disease.

Classical and cellular (atypical) congenital mesoblastic nephroma: a clinicopathologic, ultrastructural, immunohistochemical, and flow cytometric study

Sixteen cases of congenital mesoblastic nephroma (CMN) were studied. The tumors showed variable patterns of growth, degrees of cellularity, and mitotic activity. Six tumors had the classical pattern of CMN, seven were of the cellular or atypical variant and three showed combined features. The mean ages at presentation were 16 days, 5.3 months, and 2.3 months, respectively. Average size and weight were 5.1 cm and 94 g for classical CMN, 9.1 cm and 620 g for cellular CMN and 10.5 cm and 150 g for combined tumors. Cyst formation, hemorrhage and necrosis were confined to cellular CMNs and to cellular areas of combined CMNs. Mitotic activity ranged from 0 to 1/10 high-power fields (HPFs) in classical tumors to 25 to 30/10 HPFs in cellular tumors. Clear cell sarcoma-like areas were observed in three neoplasms. In ten cases there was invasion of perirenal fat; in one case each, invasion of the psoas muscle, renal vein wall, and renal vein lumen was observed. Ultrastructural and immunohistochemical studies showed features consistent with myofibroblastic differentiation. Flow cytometric analysis revealed euploidy in one classic CMN, one cellular CMN and in classic areas of a combined CMN; cellular areas of the latter tumor were aneuploid. All patients with follow-up were alive without evidence of disease after a mean period of 5 years following nephrectomy alone. No correlation was observed between the pathologic features assessed and the biologic behavior of these neoplasms.