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

Case report of an infant with congenital mesoblastic nephroma leading to pulmonary metastasis

Congenital mesoblastic nephroma is considered a tumour with favourable clinical behaviour with only few reported cases of metastases. We report an infant who underwent complete resection and later developed pulmonary metastasis. Ten-month-old baby girl initially presented at 3 weeks of age with macroscopic haematuria, hypertension and a lumbar mass. Contrast-enhanced computed tomography revealed a tumour arising from the left kidney without local invasion or metastasis. She underwent left nephrectomy. Immunohistochemistry confirmed a cellular type of congenital mesoblastic nephroma. At 10 months, she presented with difficulty in breathing. Contrast-enhanced computed tomography revealed an opacity in the right hemi-thorax. Histology of lung mass was suggestive of deposits from the previously excised mesoblastic nephroma. She developed a right-sided haemothorax and succumbed. This case report highlights the fact that even though congenital mesoblastic nephromas are considered tumours with favourable clinical behaviour, they can present later with distant metastasis. Therefore, clinicians need to be aware of this rare malignant potential and adhere to meticulous follow-up protocols.

Congenital mesoblastic nephroma: review of current management and outcomes in a single centre

BACKGROUND

Congenital mesoblastic nephroma (CMN) is a rare tumour of the kidney with an overall excellent prognosis. Once considered a benign tumour, it is now recognized to carry a risk of recurrence and metastases with subsequent poor outcomes. The potential for genetic aberrations such as ETV6-NTRK3 fusion raises the potential for targeted treatments in certain patients. The optimum mode and frequency of surveillance is unclear. This study aims to assess this institution's experience with CMN and long-term outcomes.

METHODS

A single centre retrospective review was performed of all confirmed cases of CMN between October 2001 and January 2021.

RESULTS

Nine cases of CMN in patients under 12 months of age were identified. The histopathology, management and outcomes of these patients are discussed.

CONCLUSION

CMN overall has a very good prognosis, but a subgroup does exist that will have poor outcomes. It is difficult to accurately identify this group to target adjuvant therapy.

Prenatal Course and Sonographic Features of Congenital Mesoblastic Nephroma

Background: Congenital mesoblastic nephroma (CMN) is the most common renal tumor among fetuses and infants before the age of 6 months. It usually behaves as a benign tumor. The prenatal features and outcomes of pregnancies with fetal CMN have never been systematically reviewed and analyzed, whereas neonatal or pediatric series have been published several times. The aims of this study are to (1) describe the prenatal natural course and prenatal sonographic char-acteristics of CMN; (2) determine the outcomes of pregnancies with fetal CMN; and (3) demonstrate typical sonographic images together with video clips of prenatal CMN, as an educational example based on our index case presented here. Methods: Studies focused on fetal CMN, including those consecutively published on PubMed from 1980 to June 2022 as well as the index case presented here, were identified and validated to perform a systematic review. The data of fetal imaging and the prenatal course of pregnancies were extracted for analysis. Results: The findings derived from 41 cases of review are as follows: (1) No single case has been diagnosed in the first half of pregnancy. No cases were detected during routine anomaly screening at mid-pregnancy. All cases were de-tected in the third trimester or late second trimester. (2) Polyhydramnios is very common and is the first clinical manifestation in most cases, leading to detailed ultrasound in the second half of pregnancy. (3) Preterm birth and low birth weight are the most common adverse pregnancy out-comes, resulting in neonatal morbidity. (4) Hydrops fetalis, though relatively rare, can be associated with CMN and is a grave sign. (5) Prenatal diagnosis is essential since it is critical for the antenatal plan, comprising either referral to a tertiary care center or proper surveillance to prevent serious obstetric complications, especially preterm birth. (6) Ultrasound is the primary tool for prenatal diagnosis of CMN, whereas MRI can be used as an adjunct if some other tumors are suspicious or sonographic features are not typical for CMN. Conclusion: In contrast to CMN in neonates, fetal CMN is much more serious since it significantly impacts adverse pregnancy outcomes and perinatal morbidity and mortality. The typical prenatal course and the sonographic features of CMN are described.

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.

Congenital mesoblastic nephroma: Clinical analysis of eight cases and a review of the literature

Congenital mesoblastic nephroma (CMN) is a mesenchymal renal tumor. The aim of the present study was to review the clinical characteristics and outcome of CMN in infants. A retrospective file review was conducted of eight cases of CMN treated at the Children’s Hospital of Fudan University between 2004 and 2012. Ultrasound and computerized tomography scans had been performed on all eight patients. Two cases presented with a solid tumor and exhibited pathological features consistent with those of classic CMN, five cases exhibited cystic, hemorrhagic and necrotic characteristics, with calcification and pathology consistent with the cellular variant of CMN and one case presented with a solid tumor, which exhibited pathological features consistent with ceullular CMN. Histology confirmed classic CMN in two patients and cellular CMN in six patients. For surgical intervention, four cases had radical nephrectomy, one case had a half nephrectomy and three cases had tumor enucleation performed. Two cases had received pre-operative chemotherapy, but exhibited no response, and three cases received post-operative chemotherapy. Two patients were lost to follow-up, but the remaining six patients survived to the end of follow-up without further complications. The mean follow-up time was 24.6 months. In conclusion, the differential diagnosis between CMN and Wilms’ tumor is critical. Imaging characteristics are partially correlated with pathological characteristics. Surgery is the main treatment for CMN, but pre-operative chemotherapy is not particularly effective. The efficacy of post-operative chemotherapy requires further investigation, but the prognosis is positive.

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.

Unclassified pediatric renal stromal tumor overlapping with metanephric stromal tumor and solitary fibrous tumor with diffuse S-100 protein expression

Metanephric stromal tumor (MST) is a rare pediatric neoplasm unique to the kidneys that is currently included in the spectrum of metanephric tumors, along with metanephric adenoma and adenofibroma. We herein report an unusual case of pediatric renal stromal tumor overlapping with MST and solitary fibrous tumor (SFT). Histologically, the tumor was composed of bland-looking spindle to stellate cells embedded in a fibro-sclerotic stroma that focally surrounded native entrapped renal tubules or blood vessels with abortive rings or collarettes. Alternating hypercellular and hypocellular areas and a focal hemangiopericytomatous-like vascular pattern imparted to the tumor a resemblance to SFT. Angiodysplasia of intratumoral arterioles was also observed, but juxtaglomerular cell hyperplasia was not a feature. Immunohistochemically, the neoplastic cells showed a polyphenotypic profile, including diffuse expression of vimentin and CD34, and focal immunoreactivity for alpha-smooth muscle actin, EMA, and CD99. However, the most striking finding was diffuse nuclear and cytoplasmic expression of S-100 protein. Although this protein has been reported to stain the heterologous glial and/or cartilaginous components that can be occasionally encountered in MST, this marker has not been previously reported in the fibroblastic component of MST. Pathologist should be aware of similar unusual unclassified tumors to avoid potential confusion with other benign or malignant S-100 protein-positive tumors.

[Management of antenatal fetal abdominal tumors. Clues for the diagnosis of a congenital mesoblastic nephroma]

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

Congenital Mesoblastic Nephroma

Congenital mesoblastic nephroma is a rare renal tumor of early infancy with a favorable outcome after complete surgical removal. It consists of a heterogeneous group of spindle cell tumors. Early and accurate prenatal diagnosis of the renal tumor may improve the outcome of affected pregnancies by implementing the best strategy for prenatal management and delivery. But detection of congenital mesoblastic nephroma in a fetus is rare. To the authors' knowledge, there are fewer than 30 reports of a prenatal diagnosis of a mesoblastic nephroma in the literature. This case describes the prenatal sonographic diagnosis of cellular congenital mesoblastic nephroma.

Unusual morphology in mesoblastic nephroma

Congenital mesoblastic nephroma (CMN) is a rare paediatric renal neoplasm. It is a diagnostic challenge to the pathologists due to its close differentials having ominous prognosis. We present three cases of CMN with unusual morphology including evidence of renal dysplasia in one of them.

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.

Immunohistochemical profiling of Wilms tumor: a tissue microarray study

AIM

Wilms tumor (WT) usually shows a bi-phasic or tri-phasic morphology comprised of blastemal, stromal, and epithelial cells. Other biphasic renal tumors that can mimic WT may pose diagnostic dilemmas especially in preoperative needle biopsy samples. This tissue microarray study was designed to investigate the immunohistochemical features that may prove useful in the accurate diagnosis of WT in small biopsy samples.

METHODS

Eight punches from each paraffin block of 45 cases of WTs were used to construct 5 tissue microarray blocks. Immunohistochemical reactions of blastemal, stromal, and epithelial cells of each core to a panel of 37 antibodies were evaluated.

RESULTS

Blastemal elements expressed CD56 (22, 57%), CD57 (19, 55%), cytokeratin 22 (CK22) (12, 27%), and CK8 (9, 21%). Epithelial cells were stained mostly with CK22 (17, 94%), CK18 (12, 66%), CK8 (14, 70%), CD57 (10, 76%), CD56 (6, 43%), EMA (7, 44%), and CK19 (5, 25%). Stromal cells expressed SMA (21, 50%), actin (18, 48%), desmin (9, 20%), CD34 (7, 24%), CD57 (5, 18%), and CD56 (5, 15%). Only one case was positive for CK5/6, CK13, CK14, and CK20. Calretinin expression was seen in the stromal cells of 3 and placental alkaline phosphatase expression was observed in 1 case. All 3 components were negative for CK1, CK7, myoglobin, Myf-4, MyoD1, HMB45, chromogranin A, synaptophysin, Melan A, beta-HCG, alpha-HCG, alpha-Inhibin, renal cell carcinoma antigen, glycophorin A, PSA, and estrogen and progesterone receptors.

CONCLUSIONS

CD56, CD57, CK22, CK18, CK8, EMA, SMA, and actin are useful markers for an accurate diagnosis of WT in small biopsy samples.

Imaging accuracy and incidence of Wilms' and non-Wilms' renal tumors in children

PURPOSE

The purpose of this study is to determine the actual incidence, age distribution, and preoperative imaging accuracy of non-Wilms' tumors (nWT) in children with renal masses.

METHODS

Pathologic reports from all tumor nephrectomies or open renal biopsies performed at a single institution from September 1999 to June 2005 were analyzed. Patient demographics, pathologic findings, specific imaging study descriptors, and differential diagnoses were tabulated. Accuracy of imaging studies in identifying specific tumors was calculated.

RESULTS

Ninety-two patients were identified. Sixty-eight had Wilms' tumor (WT) and 24 had an nWT. The nWT group included congenital mesoblastic nephroma (5), clear cell sarcoma (4), neuroblastoma (4), renal cell carcinoma (4), lymphoma (2), angiomyolipoma (2), teratoma (1), hemangioma (1), and renal epithelial tumor (1). When grouped by ages, the incidence of nWT was between 0% and 83%. Sensitivity, specificity, positive predictive value, and negative predictive value for computed tomography (CT) determining a diagnosis of WT were 0.92, 0.55, 0.84, and 0.73, respectively. The CT reports explicitly stated a potential diagnosis in 89% of cases, with a diagnostic accuracy of 82%.

CONCLUSIONS

Non-Wilms' tumors may represent a significant proportion of renal tumors in children, especially in children aged less than 6 months or greater than 12 years. Preoperative imaging is of limited value in differentiating these tumors. These data have significant implications for parental counseling, surgical plan, and the choice of neoadjuvant chemotherapy and argue in favor of obtaining a tissue diagnosis before instituting therapy.

A case of fetal congenital mesoblastic nephroma with oligohydramnios

Although congenital renal tumors are rare, congenital mesoblastic nephroma (CMN) is the most common renal tumor in early infancy. It is non-metastatic, well differentiated, amenable to surgical removal, and carries a good prognosis. Polyhydramnios has been detected in most of the published cases of CMN. However, we experienced a rare case of fetal CMN associated with oligohydramnios. A 28-yr old woman at 34 weeks of gestation was referred to our hospital for oligohydramnios and a fetal abdominal mass. An ultrasonography revealed a huge, well-encapsulated mass arising from the right kidney. An emergency cesarean section was performed due to fetal distress. After birth, despite intensive neonatal care, the baby died because of renal failure, disseminated intravascular coagulopathy, pulmonary edema, together with other problems.

Atypical congenital mesoblastic nephroma presenting in the perinatal period

Congenital mesoblastic nephroma (CMN) is a rare tumour of infancy having an overall good prognosis. The less common, atypical CMNs have cellular elements in them and tend to have an unpredictable course. Occurrence in the perinatal period may further change the outcome. By reporting three patients presenting in the perinatal period with atypical CMN, an attempt is made in this paper to characterize the clinical behaviour of these variant tumours. Though one of our patients had an uneventful course, the other two had several complications including polyhydramnios, prematurity, hypertension, haemodynamic instability and tumour spillage. The course was complicated by recurrence in the latter two and refractoriness to chemotherapy and death in one. That the atypical subset of CMNs occurring in the perinatal period can have a stormy course is well illustrated by this report. Possible prognostic factors are evaluated and the sparse reports of similar cases in the literature are reviewed and compared.

PRCC-TFE3 renal cell carcinoma in a boy with a history of contralateral mesoblastic nephroma

The genetics of renal tumors in children is widely recognized. However, most of the studies published to date emphasize the association between Wilms tumor and the WT-1 gene. Recently, a unique translocation between the X chromosome and chromosome 1 or t(X;1) has been described in several reports of renal cell carcinomas (RCCs) diagnosed in children and adolescents that results in PRCC-TFE3 gene fusion. We report here a 9-year old African-American boy with a history of a right congenital mesoblastic nephroma treated with nephrectomy and followed by annual checkups. After 9 years, he was diagnosed with a mass at the hilum of the left kidney during the work-up of new-onset hypertension. A limited biopsy revealed densely hyalinized connective tissue that was initially interpreted to be a hyalinized contralateral mesoblastic nephroma. The child received chemotherapy, but the mass continued to grow. He underwent a left nephrectomy, and the pathology was diagnostic for a clear cell RCC. Chromosomal analysis disclosed a t(X;1)(p11.2;q21) translocation, which is known to result in a PRCC-TFE3 gene fusion. The tumor showed nuclear labeling for TFE3 protein by immunohistochemistry, supporting the above diagnosis. He has been on hemodialysis, is tumor free, and has not been receiving chemotherapy for 24 months. This is the first report of a RCC as a second malignant neoplasm in a child treated for a congenital mesoblastic nephroma.

Renal cystic diseases: a review

This review aims to assist in the categorization of inherited, developmental, and acquired cystic disease of the kidney as well as to provide a pertinent, up-to-date bibliography. The conditions included are autosomal-dominant polycystic kidney disease, autosomal-recessive polycystic kidney disease, unilateral renal cystic disease (localized cystic disease), renal simple cysts, multicystic dysplastic kidney, pluricystic kidney of the multiple malformation syndromes, juvenile nephronophthisis and medullary cystic disease, medullary sponge kidney, primary glomerulocystic kidney disease, and glomerulocystic kidney associated with several systemic disorders mainly of genetic or chromosomal etiology, cystic kidney in tuberous sclerosis, and in von Hippel-Lindau syndrome, cystic nephroma, cystic variant of congenital mesoblastic nephroma, mixed epithelial stromal tumor of the kidney, renal lymphangioma, pyelocalyceal cyst, peripylic cyst and perinephric pseudocyst, acquired renal cystic disease of long-term dialysis, and cystic renal cell carcinoma and sarcoma. Whereas the gross and histologic appearance of some of these conditions may be diagnostic, clinical and sometimes molecular studies may be necessary to define other types.

Mixed epithelial and stromal tumor of the kidney in a 12-year-old girl

Mixed epithelial and stromal tumor of the kidney (MESTK) is a rare kidney neoplasm that almost exclusively occurs in perimenopausal women, and long-term estrogen replacement is relevant to its pathogenesis. Herein is described an atypical case of MESTK uncovered in a 12-year-old premenarcheal girl without a history of prior estrogen use. On surgical specimen it was found that the well-circumscribed tumor measuring 14 cm arose from the lower pole of the right kidney, showing solid and fibrous-cystic areas. Microscopically, it was composed both of epithelial structures similar to renal tubules and stroma comprising non-specific spindle cells. Some intratumoral tubules showed affinities to distal-nephron-specific lectins, and those immunoreactive for proximal-tubule-specific CD15 were also present. In addition, primitive ductal structures were reactive both for CD15 and lectins, but immature epithelial elements typical of nephroblastoma were absent. Spindle cells were positive for actin, desmin and vimentin, and expressed progesterone and estrogen receptors. The tumor was comparable with MESTK, although some epithelia were associated with the immunophenotype of proximal tubules. The patient was free of disease postoperatively for 40 months. In the present case, remnants of the primitive periductal mesenchyme might be promoted to neoplastic cells by a sex-steroid surge during puberty.

The spectrum of pediatric tumors in infancy, childhood, and adolescence: a comprehensive review with emphasis on special techniques in diagnosis

The spectrum of pediatric tumors varies considerably, from those derived from blastemal cells in various organ systems to proliferations of soft tissue supporting cells to hamartomatous processes that mimic malignant tumors. Small round cell tumors are often undifferentiated or poorly differentiated, making it difficult sometimes to provide a definitive diagnosis. Both benign and malignant tumors require a coordinated method for diagnosis, and need a comprehensive evaluation to provide the most appropriate diagnosis for designing therapy and predicting prognosis. Pediatric tumors require the integration of routine histopathologic examination with histochemical, immunocytochemical, ultrastructural, cytogenetic, and diagnostic molecular pathology techniques. This review provides updated guidelines with respect to the application of these special techniques in this rapidly evolving diagnostic arena.

Usefulness of immunohistochemistry in delineating renal spindle cell tumours. A retrospective study of 31 cases

AIMS

To assess the usefulness of immunohistochemistry in delineating tumour diagnoses on a series of morphologically diagnosed renal spindle cell tumours (RSCTs).

METHODS AND RESULTS

Formalin-fixed paraffin-embedded tissues from 31 morphologically diagnosed tumours were reinterpreted in light of newly obtained immunohistochemical information. By morphology, six had originally been classified as sarcomatoid carcinoma, five as spindle cell tumour (NOS), four as sarcoma (NOS), three as leiomyoma, three as leiomyosarcoma, and one each as fibrous polyp, hamartoma, neurilemmoma, mesoblastic nephroma, medullary fibroma, angiomyolipoma, haemangiopericytoma, malignant rhabdoid tumour, malignant Triton tumour, and carcinosarcoma. The application of immunohistochemistry verified the original diagnosis in 18 cases (18/31, 58%), confirming the diagnosis of sarcomatoid renal carcinoma (4/6), leiomyoma (2/3), leiomyosarcoma (3/3), sarcoma (NOS) (2/4), carcinosarcoma (1/1), malignant rhabdoid tumour (1/1), malignant Triton tumour (1/1), fibrous polyp (1/1), mesoblastic nephroma (1/1), hamartoma (1/1), and angiomyolipoma (1/1). Different tumour designations were suggested in 13 cases (13/31, 42%), including carcinosarcoma, sarcoma (NOS), leiomyosarcoma, solitary fibrous tumour, monomorphic/biphasic angiomyolipoma, endometrial stromal tumour, and congenital mesoblastic nephroma.

CONCLUSIONS

Our data indicate that although morphology is most important in formulating the initial differential diagnosis, the addition of immunohistochemistry is vital in arriving at the correct classification of RSCTs.

Mixed epithelial and stromal tumors of the kidney. A report of 22 cases

Mixed epithelial and stromal tumor of the kidney (MESTK) is a recently described subset of renal neoplasm that tends to occur in middle-aged and older women and is characterized by a distinctive histological appearance. To further characterize this lesion, we report the clinicopathological and immunohistochemical features of 22 additional cases from our institutional files. Grossly, the tumors ranged in size from 1 cm to 14 cm (mean 6.7 cm), were well circumscribed but unencapsulated, and showed a cystic cut surface. The tumors were composed of a spindle cell proliferation that resembled ovarian stroma, as well as an epithelial component lining the cystic structures, which usually consisted of flat to hobnailed cells typical of collecting-duct epithelium. Areas displaying features of Mullerian differentiation were also documented in 6 cases, including epithelium of endometrioid, tubal, clear cell and squamous cell type as well as one case showing an architecture that closely resembled Mullerian adenofibroma and adenosarcoma. Follow-up in 14 patients (average 4.4 years) showed no evidence of recurrence or metastasis. We believe these tumors represent the renal counterpart of similar mixed epithelial and stromal neoplasms occurring in the biliary tract and pancreas, which is also characterized by cystic structures lined by epithelium, admixed with ovarian-type stroma. The differential diagnosis for these tumors includes cystic nephroma and cystic partially differentiated nephroblastoma, which we believe to represent clinically and morphologically distinct entities from MESTK. In particular, the distinction from cystic nephroma in adult male patients is emphasized, and two cases of this entity are included in the study for comparison.

Gene expression profiling of mesoblastic nephroma and Wilms tumors—comparison and clinical implications

OBJECTIVES

To better understand the molecular mechanisms in the tumorigenesis and progression of mesoblastic nephroma (MN), we studied its gene expression profiles. MN is the most common tumor of the neonatal kidney. It occurs in a younger age group than the Wilms tumor (WT). To date, very little is known about the etiology and pathogenesis of MN.

METHODS

Using microarrays containing 22,943 cDNA, we analyzed the expression profiles of MN and compared its expression profiles with those of several other types of kidney tumors, including WT.

RESULTS

MN has a distinct molecular signature that clusters close to the WT, suggesting that both types of tumor share some similarity in gene expression and biology. When comparing the two profiles closely, we identified a number of genes that are commonly upregulated in both tumors, including insulin-like growth factor 2, thrombospondin 4, and mesenchyme homeo box 1. We also identified a set of genes that distinguish MN from WT, some of which may underlie the difference in their behaviors and can be used as diagnostic markers. Among this group of genes, topoisomerase II-alpha, highly expressed in WTs, is not overexpressed in MN. Immunohistochemical staining of topoisomerase II-alpha in additional cases of WTs and MNs confirmed this distinction further.

CONCLUSIONS

The results of our study demonstrated that MN has a distinct gene expression profile and that some of the newly identified genes can be potentially used as novel diagnostic markers.

Mesoblastic nephroma of infancy

This report presents features of mesoblastic nephroma, a rare benign tumor of kidney observed in perinatal period of life and highlights the role of imaging investigations in the proper management of this tumor. Awareness of this tumor may facilitate prevention and management of severe obstetric and neonatal complications and inadvertent and vigorous therapy compatible with that of Wilms' tumor can be avoided.

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.

Non-resectable congenital tumors with the ETV6-NTRK3 gene fusion are highly responsive to chemotherapy

BACKGROUND

Recently, the ETV6-NTRK3 gene fusion has been identified in both infantile fibrosarcoma and cellular mesoblastic nephroma. For both these tumors standard curative treatment has been primarily surgical with wide local excision. This has frequently involved radical and even mutilating surgery.

PROCEDURE

This report discusses three infants with congenital tumors, two congenital fibrosarcomas, and one atypical congenital mesoblastic nephroma, not easily amenable to surgical intervention.

RESULTS

All three were treated with pre-operative chemotherapy with excellent responses negating the need for amputation in two patients. In each patient, the ETV6-NTRK3 gene fusion was identified by reverse transcriptase-polymerase chain reaction (RT-PCR) in the tumor specimens.

CONCLUSIONS

Our findings suggest that the ETV6-NTRK3 gene fusion may underlie the distinctive biological properties of these tumors and may also indicate tumor chemosensitivity. In this group of patients pre-operative chemotherapy may abrogate the need for morbid surgical procedures.

Cellular mesoblastic nephroma: morphologic, cytogenetic and molecular links with congenital fibrosarcoma

Congenital mesoblastic nephroma (CMN) is a rare renal tumor of early infancy with a favorable outcome after complete surgical removal. CMN consists of a heterogeneous group of spindle cell tumors subdivided into "classical", "cellular or atypical" and "mixed" forms based on histologic features. We describe a new case of cellular CMN diagnosed by antenatal ultrasonography with complete remission five years after nephrectomy. Cytogenetic study evidenced a trisomy 11, and real time RT-PCR, but not conventional karyotype, allowed for the detection of the Tel-ETV6/TrkC-NTRK3 fusion transcript as a consequence of a cryptic t(12-15)(p13;q25). As in congenital fibrosarcoma (CFS), two Tel-ETV6/ TrkC-NTRK3 fusion transcripts different by a 42 bp insert in the TrkC kinase domain were expressed. Our observations outline the close links between cellular CMN and CFS. Both tumors have the clinical presentation and histologic features as well as identical cytogenetic and molecular markers in common. Therefore, they are likely to represent the same neoplasm, but occurring at different locations.

Prenatal diagnosis of congenital mesoblastic nephroma in mid-second trimester by sonography and magnetic resonance imaging

Although congenital mesoblastic nephroma (CMN) is a rare benign congenital renal tumor, it is the most common solid renal tumor in the newborn period. The most common presentation of congenital mesoblastic nephroma is polyhydramnios, and only one case with prenatal fetal hydrops has been previously reported. Prenatal diagnosis of CMN has previously been made on the basis of the findings of sonography in the third trimester, and magnetic resonance imaging (MRI)-based diagnosis has been reported recently. Here we report a case of prenatally diagnosed classical type CMN diagnosed at 22 + 3 weeks of gestation based on the findings of sonography and magnetic resonance imaging. The characteristic imaging findings in this case were fetal hydrops and polyhydramnios. To our knowledge, this is the youngest reported gestational age for prenatal diagnosis of CMN and it is the second case of CMN associated with fetal hydrops detected prenatally.

Large solitary fibrous tumor of the kidney: report of two cases and review of the literature

Solitary fibrous tumors are spindle cell neoplasms frequently arising in the serosal surface as well as a variety of other sites. We report two cases of large solitary fibrous tumor arising in the kidney, clinically thought to be renal cell carcinoma, in 41- and 72-year-old men. Although large in size (13.0 and 14.0 cm in greatest dimension, respectively), both lesions were well circumscribed and composed of a mixture of spindle cells and dense collagenous bands with no areas of necrosis or cystic changes noted macroscopically or microscopically. Immunohistochemical studies revealed reactivity for vimentin, CD34, collagen IV, and bcl-2 protein in both cases, with no staining for keratin, S-100 protein, or muscle markers, confirming the diagnosis of solitary fibrous tumor of the kidney. Solitary fibrous tumor of the kidney is rare but may present as a large mass that may be clinically confused with carcinoma or sarcoma.

Mixed epithelial and stromal tumor of the kidney lacks the genetic alterations of cellular congenital mesoblastic nephroma

Mixed epithelial and stromal tumor of the kidney is a recently recognized neoplasm that occurs almost exclusively in perimenopausal women. Because it frequently contains areas of smooth muscle in which epithelial structures are embedded, some have concluded that it is the adult form of congenital mesoblastic nephroma. Others have concluded that the morphology and epidemiology of mixed epithelial and stromal tumor indicate that it is unrelated to congenital mesoblastic nephroma. Although the genetic alterations of mixed epithelial and stromal tumor have not been previously elucidated, much is known about the genetic alterations of cellular congenital mesoblastic nephroma. The present study was undertaken to determine if mixed epithelial and stromal tumors have any of the genetic alterations recognized as typical of cellular congenital mesoblastic nephroma. RNA extraction was performed on formalin-fixed, paraffin-embedded tissue from 7 mixed epithelial and stromal tumors followed by reverse-transcription polymerase chain reaction to detect the ETV6-NTRK3 gene fusion. Fluorescent in situ hybridization with centromere-specific probes for chromosomes 8, 11, and 17 was performed to evaluate polyploidy of these chromosomes in 11 cases of mixed epithelial and stromal tumor. None of the mixed epithelial and stromal tumors showed any of these genetic alterations. We conclude that mixed epithelial and stromal tumor of the kidney lacks the genetic alterations typical of cellular congenital mesoblastic nephroma, is unrelated to it, and the appellation "adult mesoblastic nephroma" should not be used for these tumors.