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Congenital Mesoblastic Nephroma Detected by Prenatal Ultrasound with Postnatal and Post Operative Correlation- A Case Report

Samar Mohamed El-Maadawy¹, Sawsan Kharrat Halou¹, Diary Abdul Rahman², A.R. Mustafawi²

¹Radiology Department, Latifa Hospital, Dubai, United Arab Emirates

²Pediatric Surgery Department, Latifa Hospital, Dubai, United Arab Emirates

 

Correspondence:

Samar Mohamed El-Maadawy

Department of Radiology

Latifa Hospital

P.O Box 9115 Dubai, UAE

E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Abstract

We report the case of a 1 day old newborn with a left renal mass which was detected by prenatal ultrasound and confirmed on postnatal imaging findings. Left nephrectomy was performed at 10th day of life and histopathology exam revealed a congenital mesoblastic nephroma, cellular variant.

Keywords: mesoblastic nephroma, prenatal ultrasound, nephrectomy

 

Introduction

Congenital mesoblastic nephroma is a rare tumor with an estimated incidence of about 8 per million in children under 15 years of age [1]. It is, however the most common renal tumor in neonates, with more than 80% of congenital mesoblastic nephroma presenting in the neonatal period [2]. In 1967, Bolande et al. [3] described congenital mesoblastic nephroma as a separate entity from Wilm’s tumor and it is now considered a benign renal tumor. Nephrectomy alone is the treatment of choice with a reported survival of over 98% [4].

We present the case of a newborn who was diagnosed with solid left renal tumor by prenatal ultrasound.

Case Report

A newborn male delivered by normal vaginal delivery weighing 2.98 Kg was transferred to Latifa Hospital Neonatal Intensive Care Unit (NICU) with an antenatal ultrasound finding of a large left renal mass. Review of the ultrasound done at 37 weeks gestation revealed heterogeneous soft tissue mass overlying the left kidney measuring approximately 6.3 x 4 cm. Doppler exam showed present vascular signal. Right kidney was normal. No other fetal anomaly could be seen (Fig. 1).

Figure 1: Antenatal ultrasound at 37 weeks gestation - A:  A heterogeneous soft tissue mass was seen overlying the left kidney (solid arrow). B: On color Doppler, the mass is vascular (dashed arrow)

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Clinical examination revealed soft abdomen with marked flank fullness on the left side. Examination of other systems was unremarkable. Postnatal abdominal ultrasound showed a large pelvi-abdominal mass lesion involving the left kidney measuring at least 7.7 x 6.2 x 10.1 cm along its maximal transverse, antero-posterior and cranio-caudal diameters with positive vascular signal at color Doppler examination. Differential diagnosis was done with mesoblastic nephroma, Wilm’s tumor and less likely neuroblastoma (Fig. 2).

Figure 2: Abdominal ultrasound performed at 1st day of life. A - Extended ultrasound field view showing large solid left pelvi-abdominal mass involving the left kidney (arrow). B - Color Doppler ultrasound revealing a vascular mass with arterial flow on spectral Doppler analysis.

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Further assessment by CT examination of the abdomen and pelvis was requested which revealed a large well defined heterogeneous solid mass measuring 7.5 x 9.5 cm inseparable from the left kidney with a small remnant renal rim displaced inferiorly. The mass was crossing the midline and causing displacement of the major vessels to the right side. No calcification or invasion of the vessel could be detected (Fig. 3).

Figure 3: Post IV contrast coronal reconstructed CT image showing a large mass sparing a small rim of left renal tissue at the lower pole (arrow)

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The surgical team advised for other laboratory investigations which showed alpha-fetoprotein (AFP) >30,000 ng/mL, lactate dehydrogenase (LDH) 848 IU/L, neurone specific enolase (NSE) 23.3 ng/mL, carcinoembryonic antigen (CEA) 1 ng/ml and human chorionic gonadotropin (ß hCG) 6 IU/L.

Baby was intubated on day 10 of admission for operation. Left nephro-uretrectomy procedure was performed. Operative findings showed a large left renal tumor, replacing all the renal tissue, pushing bowel downwards and to the right. Left suprarenal gland was normal. No enlarged lymph nodes were identified. Stepwise dissection of the renal mass from the surrounding tissue was done starting from the lower pole. Tumor removed intact and sent to histopathology (Fig. 4)

Figure 4: Intra-operative image A - Surgical specimen after left nephro-ureterectomy. B - Normal appearing left supra-renal gland (arrow)

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Baby was extubated on 2nd day from surgery. Oral feeds started on postoperative day 6 increasing gradually to full oral feeds after 1 day. Histopathology report revealed congenital mesoblastic nephroma, cellular variant. The baby has underwent several ultrasound followups and is free from tumor recurrence after 13 months as showed by MRI examination of the abdomen (Fig. 5).

Figure 5: Coronal MRI at 13 months of age showing free tumor bed.

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Discussion

Mesoblastic nephroma is a rare benign mesenchymal renal tumor, arising either from the kidney or the renal fossa [5]. Malignant degeneration has occasionally been reported.[6]. Most cases are diagnosed during the third trimester. It appears as a large solid tumor, but more heterogeneous pattern has also been described. Rarely, cystic components or calcifications can be visualized. Polyhydramnios and fetal hydrops may develop in utero. Prematurity and arterial hypertension are associated findings after birth. The latter resolves with tumor removal [7]. The main differential diagnosis is Wilm’s tumor, which is extremely rare as a prenatal diagnosis. No specific ultrasound features differentiate Wilm’s tumor from congenital mesoblastic nephroma [8]. Other conditions to consider when there is fetal renal enlargement are nephromegaly related to syndromes like Beckwith-Wiedemann syndrome, renal vein thrombosis or nephromegaly related to hereditary cystic renal disease [9]. No fetal intervention is available [6].

Postnatal imaging shows a tumor with variable echogenicity and homogeneous solid tissue by ultrasound. CT and MRI show a solid, relatively homogeneous renal tumor, typically involving the renal sinus with variable contrast enhancement [10]. Neonates typically have an obvious palpable mass on examination [11]. The prognosis after surgical excision is good [5]. Nephrectomy is curative in most cases [11].

Conclusion

Fetal renal tumors are rare. Accesses to prenatal care and advances in prenatal imaging have allowed the identification of renal tumors within the fetus. Prenatal diagnosis has allowed for prompt postnatal radiological investigations and surgical intervention improving perinatal outcome.

 

 

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