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Compare to congenital mesoblastic nephroma in fetus, congenital wilms tumor is extremely rare. Herein we report a case of congenital bilateral solid masses on antenatal ultrasound. The mass was evaluated by ultrasonography and contrast computed tomography scan in postnatal period, and the patient was undergoing tumor enucleation separately in short period after neoadjuvant chemotherapy. The diagnosis was confirmed by histology analysis for each side, and the treatment was taken according to the International Society of Pediatric Oncology., (Copyright © 2021. Published by Elsevier Inc.)

Solid fetal renal masses are a rare finding on antenatal ultrasound, with hydronephrosis and cystic disease of the kidney usually being the most common causes for fetal renal enlargement. Herein we report a case of a solid fetal renal mass which was detected on third trimester antenatal ultrasound scanning. This renal mass was evaluated by MRI in the postnatal period and diagnosis confirmed by histological analysis, after surgical excision. Also discussed are the differential diagnoses and imaging features of other solid fetal renal masses, including congenital mesoblastic nephroma, nephroblastomatosis, renal sarcoma and angiomyolipoma., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

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

Objective: To review nephrectomy specimens for pediatric renal tumors seen over a period of 9 years (1995-2003)., Study Design: Specimens categorized as fetal rhabdomyomatous Wilms tumors (WTs) or teratoid WTs were selected. Corresponding fine needle aspiration cytology slides were subjected to cytomorphologic analysis., Results: Of 93 specimens of WT, 3 cases of fetal rhabdomyomatous WT and 2 cases of teratoid WT were identified. The aspirates were stromal predominant, and all of them showed rhabdomyoblasts embedded within. These stained variably green or orange on Papanicolaou stain and blue-gray on May-Grünwald-Giemsa stain. In all 5 aspirates, foci of blastema with or without tubules were identified, permitting a diagnosis of WT. A squamous morule was seen in an aspirate from teratoid WT., Conclusion: The outcome of fetal rhabdomyomatous and teratoid WTs is good, but the tumors do not shrink with chemotherapy. Identification of rhabdomyoblastic elements on aspirates can help in assessment of subsequent response to treatment.

Background: To review the clinical characteristics and survival of infants diagnosed with a primary renal tumor in the first 7 months of life., Procedure: A retrospective data review of patients registered in five large international protocols (SFOP/GPOH/SIOP9/93-01, UKW3 and NWTSG 4 and 5) spanning 1985-2002., Results: 750 (7.2%) of 10,430 registered patients were diagnosed with a renal tumor before age 213 days. Tumor types were Wilms tumor (WT) 58%; congenital mesoblastic nephroma (CMN) 18%; malignant rhabdoid tumor (MRTK) 8%; clear cell sarcoma (CCSK) 2%; non-Wilms tumor (unspecified) 6%; histology unknown, 9%. CMN predominated among tumors diagnosed in the first month of life (54%) but its relative contribution diminished to <10% of all cases diagnosed after the age of 3 months (P < 0.001). Among 639 cases with specified histology and stage, 9/11 stage IV tumors were MRTK, 37/39 bilateral tumors were WT. In 626 children where surgical approach was specified, 522 had immediate nephrectomy. For all cases, 5 years event-free survival (EFS) was 80% and overall survival (OS) 86%. Five years EFS and OS respectively by tumor type were WT (86%, 93%), CMN (94%, 96%), CCSK (49%, 51%), MRTK (16%, 16%)., Conclusion: Renal tumors diagnosed in the first 7 months of life generally have an excellent prognosis though histology is an important prognostic factor. In the first 2 months of life the prevalence of CMN is high. The relative occurrence of WT increases rapidly with age thereafter. Bilateral tumors are usually WT. Tumors with metastases at diagnosis are usually MRTK., ((c) 2007 Wiley-Liss, Inc.)

Unlabelled: Tumors diagnosed during the first month of life are infrequent: 0.5 to 2% of all childhood neoplasms. This is an interesting group of tumors because their type, relative incidence, natural history and response to treatment differ from those seen in older children., Aim: To contribute the experience of our institution in congenital tumors the last 13 years., Material and Methods: The records of all neonates (< 31 days old) diagnosed with solid tumors since January 1990 to December 2002 have been retrospectively reviewed., Results: Twenty-seven neonates have been diagnosed with tumors in the last 13 years. Thirteen patients (48%) were prenatally diagnosed. Nine babies were diagnosed at the initial neonatal exam (40% of those diagnosedd after birth). Neuroblastoma was the commonest tumor (10 cases, 37%), of which 4 were stage I, 4 stage IV-S and 2 stage III. There were 8 teratomas (3 sacrocoxigeal, 1 retroperitoneal, 1 in the CNS, 1 orbitary and two oronasal), two hepatic tumors (1 hepatoblastoma, 1 hemangioendothelioma, two CNS tumors, two giant nevus (one on a hamartoma), and one each Wilms tumor, infantile fibrosarcoma and myofibroblastic tumor. Treatment was surgical resection alone in 17 cases (68%) and surgery + chemotherapy in 8 (32%) (5 neuroblastomas, one CNS tumor, one Wilms tumor and one presacral teratoma who developed a yolk sac tumor); 3 patients died (11%): one at surgery, one of tumoural airway obstruction at birth and one with craniopharyngioma. Among the 14 tumors that were initially not malignant, two can be locally agressive, one was an immature teratoma, the giant nevus with hamartoma developed in situ melanoma, the other nevus had meningeal melanosis with hydrocephalus, and one mature presacral teratoma developed a yolk sac tumor., Conclusions: Diagnosis of congenital tumors is performed earlier in recent years due to the wide use of prenatal ultrasound. Their natural history is more benign than in other age groups, except for CNS tumors and very large or obstructing tumors. The histological patern is not determinant of the outcome. Complete surgical excision is the treatment of choice, most cases not need adjuvant chemotherapy. We ought to pass this message on to our colleagues in prenatal diagnosis, so parents get reliable information.

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.

Congenital hemihypertrophy is an uncommon condition of unknown etiology characterized by unilateral overgrowth of part or all of one side of the body. Hemihypertrophy is known to be associated with certain childhood tumors, most notably Wilms tumor (or nephroblastoma), and for this reason infants with hemihypertrophy are often followed with serial abdominal ultrasounds. Klippel-Trénaunay syndrome (KTS) is the triad of port-wine stain, venous varicosities, and soft tissue and/or bony hypertrophy. Children with KTS typically have localized rather than generalized hemihypertrophy, but occasionally the hypertrophy is more extensive than the vascular anomaly itself. Information is lacking about whether hemihypertrophy in this setting can also be a risk factor for Wilms tumor. We systematically reviewed the medical literature to determine whether well-documented cases of Wilms tumor in the setting of both hemihypertrophy and vascular anomalies have been described, and if found, whether the association was sufficiently frequent that routine screening for Wilms tumor in this setting should be recommended. A review of case reports and case series in the pediatric population was undertaken using specific inclusion and exclusion criteria. We found 4 of 58 subjects with hemihypertrophy and Wilms tumor had a reported vascular anomaly, but in only one case was a clear-cut diagnosis of KTS confirmed. The relationship of the other three vascular anomalies reported was of uncertain significance. In conclusion, our review suggests that the risk of Wilms tumor in the setting of localized soft-tissue hypertrophy in conjunction with a vascular malformation is quite low. More extensive hemihypertrophy extending to body sites remote from the vascular malformation itself could have a higher risk of Wilms tumor, although the magnitude of this risk is uncertain. Our findings suggest that routine serial abdominal ultrasounds in patients with vascular malformations in association with localized soft-tissue hypertrophy are unwarranted.

The literature on congenital and hereditary tumours in pigs was reviewed. One hitherto unreported own case was added. Sporadic cases of congenital tumours included several types found in newborn piglets. Embryonic tumours (nephroblastoma, rhabdomyosarcoma) occurred either in newborn or in juvenile animals. Cardiac rhabdomyomas were provisionally classified as hamartomas. The hereditary tumours, melanomas and lymphomas, were reproducible by experimental matings. These tumours are particularly interesting as models to elucidate genetic and immunologic mechanisms of tumour diseases. Striking is the high degree of regression in porcine melanomas and the associated melanosis.

We describe a case of congenital nephroblastoma (Wilms' tumor) presenting at 28 weeks of gestation with fetal hydrops and polyhydramnios. Prenatal diagnosis was made by biopsy. An emergency Cesarean section was performed due to deterioration in the cardiotocograph. A post-mortem examination confirmed the diagnosis of congenital nephroblastoma.

Unlabelled: Multicystic segmental renal dysplasia is rare in early childhood. We report a case with prenatally recognized renal malformation. Prenatally a cystic renal malformation was detected sonographically; postnatally further evaluation was performed by Doppler sonography, contrast enhanced CT and voiding cysto-urethrography leading to the diagnosis of a multicystic segmental nephroma. Due to increasing size in spite of therapeutic and diagnostic sonographic guided punctures and the atypic manifestation the baby underwent heminephrectomy. The final histological diagnosis confirmed preoperativ findings., Conclusion: Prenatally recognised cystiform renal malformations should be reevaluated postpartally by ultrasound and--as doubtful findings are found--further imaging might be necessary for follow up and for the decision on conservative or operative treatment.

Mesoblastic nephroma, a benign tumor, is the most common renal neoplasm in neonates. Wilms' tumor (WT) may occur in newborn infants, but is more common in older children. The molecular genetics of WT involves one or more genes located on Chromosome #11 and probably other locations not yet elicidated. Germline mutations cause less than 5% of WTs; most WTs are sporadic. Precursor lesions to WT called nephrogenic rests may be detected before evolution to WT by imaging studies. Developmental anomalies comprising several different syndromes are associated with nephrogenic rests and predisposition to WT. Prospective surveillance for WT may be feasible in high risk infants identified on the basis of physical findings followed by testing for predisposing gene defects and periodic imaging of the kidneys and other organs at risk until the period of risk has ended.

Recent advancement in the cytopathologic features produced a number of variants of Wilms' tumor which are the primary determinant of survival of Wilms' tumor patients. This study was carried out with 47 patients of Wilms' tumor in different stages in three selected hospitals from 1991 to 1993. Among them 61.7% (29) were in Favorable histopathology and 38.3% (18) were in Unfavorable histopathology group. After managing the patients with multimodal therapy according to the protocol of National Wilms' tumor Study-III the favorable group had shown better prognosis. The difference between two groups was statistically significant (chi-square = 3.2, P < 0.05). Histopathological variations could be easily determined which might improve the overall prognosis of Wilms' tumor.

Thirty two cases of solid tumours in newborns and infants were observed by the authors over a 15 year period. The most common type of tumours were soft tissue tumours (n = 8), neuroblastomas (n = 7), nephroblastomas (n = 5) and germ cell tumours (n = 5). Other types of embryonal tumours such as retinoblastoma and hepatoblastoma were observed in four children and non-Hodgkin's lymphomas in three children. Of 25 children followed up 18 survived. Five children died of their tumours and two children died of causes unrelated to their basic disease. Analysis of the fate of the patients and the effect of the therapy is made. It is concluded that malignant tumours prevail in infancy (90.6% of all cases). The percentage of patients treated successfully with insignificant risk for consequences from radiotherapy and chemotherapy is also high (72%).

A preterm boy was born at 34 weeks. Prenatal ultrasonography showed oligohydramnios, fetal ascites, large kidneys, and small thorax. He died 21 h after birth of respiratory insufficiency. Autopsy revealed Potter's-like facies, hypoplastic lungs, ascites, and bilateral nephromegaly (renal weight almost 10 times normal). The kidneys were finely nodular externally, solid, and cerebriform on cut section. Histologically, they showed a diffusely distorted architecture of jumbled lobules, hyperplasia of cortical-type tissue with inconspicuous proximal tubules, relative hypoplasia of medullary tissue, tubulointerstitial dysplasia, and perilobar nephrogenic rests. The renal features represent a variety of the universal or panlobar (also called pancortical or infantile) type of nephroblastomatosis. To our knowledge, this is only the third such case reported. In the brain, each lateral ventricle contained a yellow gelatinous mass. Histologically, the masses consisted of a pseudomyxoid matrix with delicate fibers and focal adipocyte clusters, all confined within choroid plexus. We consider these lesions fibrolipomatous hamartomas.

A unilateral cystic renal process discovered prenatally was removed in a neonate. Dysplastic cysts were associated with diffuse (both intra- and perilobar) nephroblastomatosis. We describe a comprehensive immunohistological study confirming the transition observed on simple histology between the different structures: nephrogenic rests (CD9+, CD24+/-, CD56+/-), glomeruloid bodies (CD10++, CD35++), ducts lined by columnar epithelium (CD9+, CD24+, CD56++), cysts lined by cuboidal or thin epithelium (some cells CD10+, CD26+, others EMA+, CD24+). Although no typical S-shaped bodies are seen, small cysts and ducts with a columnar epithelium are considered similar. The dysplastic primitive ducts are KL1++, vimentin+/-, CD9+, CD24+. With a view to assessing dysplastic preneoplastic potential, the value of CD56 and Ki67 as activation antigens with possible prognostic significance is discussed.

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.

We report the case of a premature female newborn of the 35th gestational week with a congenital mesoblastic nephroma. The tumor was prenatally diagnosed in the 32nd week of gestation. By close sonographic controls, rapid enlargement was verified towards the end of the 35th week of gestation. This was probably caused by hemorrhage into the tumor. Anemia and postnatal disseminated intravascular coagulation followed. Cesarean section was done, because the anemia was suspected by Doppler sonographic evaluation. Disseminated intravascular coagulation could not be sufficiently controlled by conservative means but only by surgical removal of the tumor. The tumor turned out to be a congenital mesoblastic nephroma by histologic evaluation. Despite postoperative anuria and catecholamine dependency, our patient eventually showed a very favourable outcome. Diagnosis, clinical behavior and therapy of this tumor with a generally good prognosis are described and discussed.

Eight cases of congenital mesoblastic nephroma (CMN) were examined. Three CMNs were of the classical (typical) variant, two were cellular (atypical), and three showed a mixed pattern. A panel of nephron segment-specific tubular epithelial markers (the lectins Tetragonolobus purpureas, Phaseolus vulgaris erythroagglutinin, and Arachis hypogaea and antibodies to epithelial membrane antigen, cytokeratin, and Tamm-Horsfall protein) were used to differentiate epithelial structures within the tumor. Antibodies against vimentin, desmin, and muscle-specific actin were used as mesenchymal markers. A monoclonal antibody to the long (embryonic) form of polysialic acid (PSA) on the neural cell adhesion molecule was used as a putative renal oncodevelopmental marker. An antibody to proliferating cell nuclear antigen also was applied, which revealed increased proliferative rate in cellular CMNs. In addition to clearly entrapped native renal tubules, CMNs contain tubular structures with immature, dysplastic epithelium and occasional epithelial cell clusters embedded deep within the tumor. These immature tubules and clusters express distal nephron, including collecting duct markers and, occasionally, vimentin and PSA. We propose that these primitive tubules and epithelial structures may originate from the ureteric bud. An epithelial differentiation of the tumor cells also is possible. In one pure cellular CMN and two mixed CMNs the cellular component showed diffuse staining for PSA. The PSA (neural cell adhesion molecule) expression of the cellular component suggests that CMN may originate from the uninduced nephrogenic mesenchyme.

The case of an infant with congenital mesoblastic nephroma and associated reninism is presented. The patient was a 39-day-old boy who presented with a left abdominal mass and mild hypertension (112/70 mm Hg). Both plasma renin activity (PRA) and plasma total renin concentration (PTRC) were elevated; the PTRC value of 1458 pg/mL of this case was the highest we had seen in patients with childhood renal tumors. The tumor was successfully removed and histologically confirmed as a congenital mesoblastic nephroma (cellular variant). The patient's PRA and PTRC returned to normal after nephrectomy. Indirect immunoperoxidase staining showed renin localized predominantly in the juxtaglomerular apparatuses adjacent to the glomeruli entrapped by the tumor. No positive staining was seen in the tumor cells. These findings indicate that the entrapped glomeruli may play a significant role in producing renin. More important, PTRC was extremely high compared to the moderate increase of PRA and to the mild elevation of blood pressure. The mechanism of renin production by childhood renal tumors is discussed, and the importance of studying inactive renin and total renin is emphasized.

Cytogenetic analysis of tumour material from a congenital mesoblastic nephroma is reported. Two cell lines were found, one with a normal 46,XY karyotype and the other with a hyperdiploid 51,XY karyotype, including a rearrangement of chromosome 11 at 11p15. This finding is of interest since loss of allelic heterozygosity at polymorphic 11p15 loci has been described in sporadic Wilms' tumour [1], and both cytogenetic [2] and molecular [3] changes of 11p15 are found in the Wiedemann-Beckwith syndrome, a condition with a predisposition to embryonal tumours, particularly Wilms' tumour. Our results lead us to speculate on the implications relating to the pathogenesis of this relatively benign tumour variant with respect to the current understanding of the genetics of Wilms' tumour.

A case of congenital mesoblastic nephroma in a 60-year-old female patient is described. The clinical onset was gross hematuria of 48 hours evolution and pain in the right renal fossa which irradiated to the iliac fossa of the same side. A routine pathological analysis was carried out on the surgical specimen including an extensive immunohistochemical analysis which was highly positive for keratin in the epithelial lining of the tubular and cystic structures and for desmine and vimentin in the fusocellular stroma of the tumor. The different histogenetic hypotheses are discussed. The importance of a precise anatomopathological diagnosis in order to institute adequate treatment is underscored.

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.

A review of 78 renal tumors in patients under 6 months of age revealed 35 congenital mesoblastic nephromas (CMNs). Based on cellular criteria, 14 were classified as classical, 4 as partly cellular, and 17 as cellular CMN. The mean ages were 24, 11, and 70 days, respectively. There were 13 intrarenal tumors (stage I) but 9 classical, 3 partly cellular, and 5 cellular CMNs extended to the perirenal fat (stage II) and 5 cellular tumors ruptured (stage III). In order to assess cellular proliferative activity, silver staining of nucleolar organizer region (Ag-NOR) proteins was performed on 19 CMNs. The number of Ag-NOR dots per cell was significantly lower in classical and partly cellular CMN than in cellular CMN, whatever the stage (P < .01). Within the cellular CMNs, the mean number of Ag-NOR dots was statistically higher in the single case that recurred with fatal outcome (P < .02). Counting of Ag-NOR dots appears to be a reproducible method for evaluating the biologic potential of CMNs. The number of Ag-NOR dots, DNA content measurements, the histological subclassification, and the presence or absence of tumor at the surgical margins may be useful features in selecting those patients who will benefit from further treatment after nephrectomy.

A case of atypical or cellular variant of mesoblastic nephroma is reported. This rare tumor, variant of the classical congenital mesoblastic nephroma, described in 1967 by Bolande, has no pejorative prognostic significance in the child under 3 months. It must be distinguished from the highly aggressive clear cell sarcoma of the kidney.

A 3-month-old baby boy presented with a right-sided abdominal mass that was shown on radiographic and ultrasonographic examination to be cystic and within the kidney. Histological examination of the right nephrectomy specimen showed it to be a congenital cystic mesoblastic nephroma. The patient made an uneventful recovery and there were no signs of recurrence eight years later. Though this tumour is extremely rare it should be considered as a differential diagnosis in infancy as its prognosis and treatment are different from those of other tumours.

Congenital mesoblastic nephroma CMN is an extremely rare renal tumor in adults, basicly seem in the childhood and, similar in some aspects to Wilms tumors. We present herein the first primary CMN in an adult older than 40 years and review the literature update. Three years after his operation (1991) the patient is clinically and echographically free of hepatic or abdominal recurrences. He has good renal function as determine by renogram, IVP and a normal serum creatinine.

Exposure of rat embryos to 3,3-dimethyl-1-phenyltriazene (DMPT) results in numerous malformations, but the urogenital system is not affected. In contrast, exposure of rat fetuses to DMPT has been reported to result in renal neoplasms, which were not further classified. To better understand this discrepancy in organotropism of the teratogenic and transplacental carcinogenic processes, the present study was undertaken to characterize the neoplasms induced in rat fetuses exposed to DMPT in utero. Renal neoplasms and persistent mesenchyme were observed in 19.2 and 11.5%, respectively, of the offspring of rats treated with 1 mg DMPT/kg body weight intraperitoneally on gestation days 16, 18, and 20. The majority of these renal lesions were observed in females. The renal neoplasms were mixtures of various types of mesenchymal tissue derivatives including smooth muscle and fibrous connective tissue. These neoplasms would be classified as renal mesenchymal tumors in rats. Brain neoplasms (numerous types), compound odontomas, and micrognathism were observed predominantly in male offspring from the same group. This treatment also resulted in decreased body weights, increased incidence of sudden loss of body weight, tremors and ataxia, and hypoplastic testes. Exposure to single intraperitoneal doses of DMPT on gestation day 20 did not produce a classic dose-response pattern: Minimal effects were observed with 10 mg DMPT/kg (occasional renal mesenchymal tumors and brain neoplasms), marked effects were observed with 30 mg DMPT/kg (lower incidence rate of most of the alterations observed with 1 mg/kg on gestation days 16, 18, and 20), and no effects were observed with 60 mg DMPT/kg. DMPT administered intraperitoneally at 1 mg/kg body weight on gestation days 16, 18, and 20 is an animal model of transplacental chemically induced renal neoplasms, which provide lesions with similarities to both intralobar nephrogenic rests and congenital mesoblastic nephroma of humans. Why the kidney is a carcinogenic target and not a teratogenic target remains unknown.

The cytologic features of congenital mesoblastic nephroma (CMN) as recognized in smears of fine-needle aspirated cytology (FNAC) are reported. These included spindle- and tadpole-shaped cells with round to oval nuclei having small nucleoli and a smooth contour. The cytoplasm of these cells was dense and homogeneously stained. The background was composed of mucoid fibrillar material. The findings appear to be different from other types of renal tumors in infancy and specific enough for this tumor to allow diagnosis by FNAC.

Fifty-six renal neoplasms reviewed by the National Wilms' Tumor Study Pathology Center presented with histologic features that resulted in confusion with rhabdoid tumor of kidney, a usually lethal childhood renal tumor; all were eventually diagnosed as other entities. Conspicuous filamentous cytoplasmic inclusions or large nucleoli, typical findings in rhabdoid renal tumors, were the usual source of diagnostic difficulty. Most, but not all, tumors occurred in pediatric patients. Sixteen were examples of Favorable Histology Wilms' tumor, which invited confusion with rhabdoid tumors either on the basis of filamentous cytoplasmic inclusions (15 cases) or macronucleoli (one case). In most cases, foci of typical Wilms' tumor blastemal aggregation or evidence of definitive nephrogenic differentiation facilitated the correct diagnosis. All 10 patients for whom information about outcome was available were alive at last follow-up. The other 40 renal lesions mimicking rhabdoid tumor of kidney consisted of a clinically and histogenetically diverse group of neoplasms, including anaplastic Wilms' tumor, congenital mesoblastic nephroma, renal cell carcinoma, transitional cell carcinoma, collecting-duct carcinoma, oncocytoma, rhabdomyosarcoma, malignant neuroepithelial tumors, and lymphoma. Most of these lesions could be separated from renal rhabdoid tumors and correctly classified on the basis of careful attention to light microscopic details, but in several cases electron microscopy or immunocytochemical studies were helpful or essential.

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 is a rare tumor of infancy that usually presents as an asymptomatic abdominal mass. A full-term newborn infant with an atypical variant of this neoplasm developed hemorrhagic shock and disseminated intravascular coagulation. The stormy course was complicated by persistent fetal circulation and then the inability to withdraw ventilatory support due to the mass effect of the tumor. After the removal of the tumor at 10 days of age, transient conjugated hyperbilirubinemia developed. At 15 months of age, the infant was thriving without evidence of recurrence of the tumor.

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.

In a nationwide study (1980-1988) for the diagnosis and treatment of Wilms' tumours (nephroblastomas), which are highly malignant embryonal mixed tumours of the kidney and show distant metastases at the time of diagnosis in 10-20% of cases, 78% of 373 children had a standard type Wilms' tumour, 7% had benign variants and 14% had high grade malignancy variants of the classical type. 20 of the 25 benign variants occurred in infants. From the 25, 16 tumours were congenital mesoblastic nephromas, 14 of which occurred in infants. As the detection of a solid renal tumour mass in the prenatal sonogram (showing an echotexture resembling that of the liver) may suggest Wilms' tumour, we analysed 11 neonates (1-14 days old), in which Wilms' tumours had been diagnosed (n = 11; 2.9%) for the histological subtype. In 9 of the 10 neonates, the final diagnosis was congenital mesoblastic nephroma. These congenital mesoblastic nephromas are cured by surgery alone. Thus, if a solid renal tumour suspected as a Wilms' tumour, is prenatally detected, the most probable diagnosis is that of the benign variant congenital mesoblastic nephroma, and, in this case, preterm delivery (e.g. to prevent metastasising and to start treatment as early as possible) is not indicated.

The autopsy finding of congenital mesoblastic nephroma in a stillborn hydropic fetus is reported. We discuss the pathogenetic relation of both entities and summarize the optimal therapeutic attitude to follow in order to prevent this misfortunate outcome.

Congenital mesoblastic nephroma (CMN) is a rare, generally benign renal tumor. A better knowledge of its natural history has changed the therapeutic approach. Currently, aggressive therapy must be exclusively reserved for the sarcomatous forms or Wilms' tumor with sarcomatoid features. The cell variant reported in our series was treated with efficacy by surgery alone. Early recognition of the lesion, preferably prenatally, is warranted in order to perform surgery early or detect hydrops fetalis, a possible complication of pregnancy.

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.

Congenital mesoblastic nephroma (CMN) is a rare renal tumor with a distinct pathology and a unique clinical, therapeutic, and prognostic pattern. The characteristic pathological feature is uniform mesenchymal spindle-shaped cells arranged in interlacing bundles. The prognosis of typical CMN is believed to be excellent by nephrectomy alone. We report a typical case of congenital mesoblastic nephroma which was prenatally detected, and was associated with maternal polyhydramnios.

In the past two years seven cases of foetal abdominal mass were observed prenatally and operated on within 30 days of life. In four of seven cases no abdominal mass was ever palpable neither at birth nor under anaesthesia just before laparotomy, whereas in all cases it was both sonographically and surgically detected. The authors stress the importance of perinatal ultrasound monitoring to cope early with clinically undetectable abdominal mass. Furthermore, they emphasise that the necessary condition for definition of a mass should by now be that it is palpable and seen via ultrasound, but a perinatal ultrasound image of mass is sufficient to warrant careful detailed clinical evaluation.