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.
A single centre retrospective review was performed of all confirmed cases of CMN between October 2001 and January 2021.
Nine cases of CMN in patients under 12 months of age were identified. The histopathology, management and outcomes of these patients are discussed.
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.

OBJECTIVE: Our goal was to summarize current literature related to imaging of intra-abdominal genitourinary tumors diagnosed in the prenatal or neonatal period. Our specific interests included modalities used, diagnoses made, changing incidence of tumor detection, and proposed future uses of these imaging modalities.
RESULTS: Fetal and neonatal MRI have been used as an adjunct to ultrasound for better characterization and assessment of congenital mesoblastic nephroma, juvenile granulosa cell tumor, and other tumors. Despite recent literature describing fetal and neonatal MRI, it is not yet possible to determine whether its use is changing the incidence of tumor detection. Improvements in imaging technology, specifically the use of fetal MRI, have allowed for earlier identification of genitourinary masses with improved capability for diagnosis, surveillance, surgical planning, and sometimes prenatal treatment of the malignancy and related diagnoses, with a goal of preventing pregnancy and delivery complications.

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

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

BACKGROUND: Cellular mesoblastic nephroma is rare after infancy, and there are many controversial reports about its clinical presentation and treatment as well as outcome in infants, young children, and adolescents.
OBJECTIVE: In this report, we will discuss our experience with four cases of cellular mesoblastic nephroma presented from infancy to childhood (from 18 months of age to 11 years of age).
METHODS: During 10 years, we had the experience of 4 cases of pediatric renal tumor with the diagnosis of cellular mesoblastic nephroma, which have been followed between 1 year and 6 years. There were three male and one female patients with the age of 1.5, 2, 2, and 11 years. These tumors showed variable characteristics according to the number of mitosis, proliferative rate, necrosis, immunohistochemical markers, and metastatic potential; however, despite of all of these variabilities, all of these patients have done well and all have been well at the end of study.
CONCLUSIONS: Pediatric renal tumors with the histologic diagnosis of cellular mesoblastic nephroma have good outcome even with metastasis, mitosis, and high proliferative rate.

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

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

It has been reported that germline DICER1 mutations correlate with a distinctive human disease syndrome. Many published studies within this field have been conducted based on rare cases. We systematically searched bibliographic databases, including PubMed, Embase, and COSMIC for articles which are related to diseases covered by DICER1 syndrome. The weighted summary of mutation frequencies among patients with pleuropulmonary blastoma (PPB), cystic nephroma (CN), and Sertoli-Leydig cell tumor (SLCT) were calculated. Forty-nine eligible articles were included. In total, 72 cases with multimorbidity of DICER1 syndrome were identified. More females (n=46, 64%) presented with multimorbidity than males (n=18, 25%) and the remaining 8 patients\' sex were unknown. Nineteen of 72 patients with multimorbidity suffered from another disease that was not yet included in DICER1 syndrome, which would provide potential phenotypes of DICER1 syndrome. The germline DICER1 mutation frequencies in PPB, CN, and SLCT were 66.9%, 73.2%, and 57.1%, respectively. The somatic DICER1 mutation frequencies of PPB, CN, and SLCT were 92.4%, 87.9%, and 43.3%, respectively. Majority of patients with multimorbidity of DICER1 syndrome were mutation positive individuals so that multimorbidity may suggest the possible germline mutation of these patients and their relatives.

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

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