Congenital mesoblastic nephroma associated with polyhydramnios and hypercalcemia

Abstract

Congenital mesoblastic nephroma (CMN) can present with atypical clinical and imaging findings. A premature male neonate was born to an 18-year-old woman after 33 weeks' gestation, which was complicated by polyhydramnios and placenta abruptio. A right abdominal mass was diagnosed antenatally. From the 1st day of life, the newborn had hypercalcemia with initially normal parathormone levels and polyuria for the first hours of life and normal urine output afterwards. Ultrasonographic study and magnetic resonance imaging of the abdomen showed at the upper pole of the right kidney a heterogeneous, solid, poorly defined mass, partially surrounded by a subcapsular fluid collection mimicking malignant rhabdoid tumor of the kidney. Surgical resection revealed a CMN of mixed, classic, and in areas, cellular type. One year after the resection, the patient is asymptomatic and normocalcemic. In conclusion, CMN may present with atypical clinical and imaging findings, necessitating an extensive work-up in order to exclude highly malignant renal tumors of the neonatal period.

Congenital Mesoblastic Nephroma Presenting with Neonatal Hypertension

“…1 Hypertension due to hyper-reninism has only been reported in nine cases of CMN, of which six were neonates. In all the reported cases, including the present one, the blood pressure and renin normalized postoperatively.…”

“…2 Some cases of CMN present in the antenatal period with polyhydramnios (10%). 1 This is thought to be related to impaired GI function, increased renal blood flow or impaired renal concentrating ability with or without hypercalcemia. 1 In our case, polyhydramnios was noted on antenatal scan at 28 weeks.…”

“…1 This is thought to be related to impaired GI function, increased renal blood flow or impaired renal concentrating ability with or without hypercalcemia. 1 In our case, polyhydramnios was noted on antenatal scan at 28 weeks. It is judicious to evaluate the fetal renal tract thoroughly in all cases with polyhydramnios.…”

“…At MRI, Wilms' tumor demonstrates low-signal intensity on T1-weighted images and high-signal intensity on T2-weighted images. 1,9 It may be impossible to distinguish congenital mesoblastic nephroma from Wilms' tumor by any radiographic study. 2 Earlier presentation and usual unilateral involvement may suggest mesoblastic nephroma, but histology is the only means of confirming the diagnosis.…”

“…1 It is, however, the most common renal tumor in neonates, with more than 80% of CMN tumors presenting in the neonatal period. 2 In 1967, Bolande et al 3 described CMN as a separate entity from congenital Wilms' tumor and it is now considered a generally benign renal tumor (as opposed to its variant, the atypical mesoblastic nephroma; AMN).…”