Cellular mesoblastic nephroma in infants and children: Report of four cases and review of the literature

A massive primary congenital mesoblastic nephroma was successfully managed through open total nephrectomy: a case report

Background

Congenital mesoblastic nephroma is the most common renal tumor in children under the age of 6 months, comprising 3-10% of all kidney tumors in children. It is a rare and mostly benign tumor. It divides into cellular, classic, and mixed subtypes. It is typically detected in the third trimester of pregnancy using ultrasonography and magnetic resonance imaging. The best treatment is surgically by completely removing the tumor.

Case presentation

We reported a case of a one-day-old female who was born at 31 weeks gestation weighing 1670 g. Preterm labor was due to polyhydramnios, which was diagnosed predelivery. A large mass was detected in the left hypochondrium using computerized tomography, total nephrectomy was performed, and the histopathological examination of the specimen confirmed the diagnosis of congenital mesoblastic nephroma.

Clinical discussion and conclusion

Early polyhydramnios could be the most significant sign of renal tumors in infants, especially congenital mesoblastic nephroma.

Report and follow-up on two new patients with congenital mesoblastic nephroma

BACKGROUND

Tumors are rare in neonatal age. Congenital mesoblastic nephroma (CMN) is a usually benign renal tumor observed at birth, or in the first months of life. It may also be identified prenatally and associated with polyhydramnios leading to preterm delivery. Effective treatment is surgical in most cases, consisting in total nephrectomy. In literature, very few studies report on the neonatal management of such a rare disease, and even less are those describing its uncommon complications.

CASES PRESENTATION

We report on two single-center newborns affected with CMN. The first patient is a preterm female baby, born at 30+ 1 weeks of gestation (WG) due to premature labor, with prenatal (25 WG) identification of an intra-abdominal fetal mass associated with polyhydramnios. Once obtained the clinical stability, weight gain, instrumental (computed tomography, CT, showing a 4.8 × 3.3 cm left renal neoformation) and histological/molecular characterization of the lesion (renal needle biopsy picture of classic CMN with ETV6-NTRK3 translocation), a left nephrectomy was performed at 5 weeks of chronological age. The following clinical course was complicated by intestinal obstruction due to bowel adherences formation, then by an enterocutaneous fistula, requiring multiple surgical approaches including transitory ileo- and colostomy, before the conclusive anastomoses intervention. The second patient is a 17-day-old male term baby, coming to our observation due to postnatal evidence of palpable left abdominal mass (soon defined through CT, showing a 7.5 × 6.5 cm neoformation in the left renal lodge), feeding difficulties and poor weight gain. An intravenous diuretic treatment was needed due to the developed hypertension and hypercalcemia, which regressed after the nephrectomy (histological diagnosis of cellular CMN with ETV6-NTRK3 fusion) performed at day 26. In neither case was chemotherapy added. Both patients have been included in multidisciplinary follow-up, they presently show regular growth and neuromotor development, normal renal function and no local/systemic recurrences or other gastrointestinal/urinary disorders.

CONCLUSIONS

The finding of a fetal abdominal mass should prompt suspicion of CMN, especially if it is associated with polyhydramnios; it should also alert obstetricians and neonatologists to the risk of preterm delivery. Although being a usually benign condition, CMN may be associated with neonatal systemic-metabolic or postoperative complications. High-level surgical expertise, careful neonatological intensive care and histopathological/cytogenetic-molecular definition are the cornerstones for the optimal management of patients. This should also include an individualized follow-up, oriented to the early detection of any possible recurrences or associated anomalies and to a better quality of life of children and their families.