Fetal Congenital Mesoblastic Nephroma: Case Report

Abstract

Congenital mesoblastic nephroma (CMN) is a rare renal tumor, but the commonest tumor of early infancy. It can be detected prenatally as a renal mass and is associated with prematurity, polyhydramnios, and neonatal hypertension. We report a case of congenital mesoblastic nephroma which presented as a large unilateral solid renal mass detected at 33 weeks of gestation associated with oligohydramnios and small for gestational age (SGA) fetus. Ultrasound features were a large hypoechoic mass arising from the upper pole of the Left kidney measuring 52 9 43 9 32 mm. Inside the mass there were incomplete septae and a few cystic areas, likely hemorrhagic areas, with minimal peripheral vascularity. The mass was surrounded by a hyperechoic capsule. The left adrenal gland could be imaged separately. The baby was delivered by a lower segment cesarean section (LSCS) at 38 weeks of gestation. After birth, the baby presented with a mass per abdomen with no other symptoms and no hypertension. CT scan and ultrasound guided biopsy confirmed the finding of the cellular variant of congenital mesoblastic nephroma. Left radical nephrectomy with adrenal gland conservation was performed on day 8 of life. Postoperative adjuvant chemotherapy was administered. On follow-up, the baby is asymptomatic with no relapse or metastasis. Fetal CMN and Wilms tumor have overlapping ultrasound features and are difficult to differentiate on prenatal ultrasound. Prenatal detection of fetal renal tumors and timely neonatal management improve perinatal outcome.