Prenatal diagnosis of fetal congenital mesoblastic nephroma by ultrasonography combined with MR imaging: A case report and literature review

Abstract

Rationale: 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.

Patient concerns: 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).

Diagnosis: CMN was detected by antenatal ultrasonography and MRI as a fetal right renal mass at 35 weeks of gestation in our hospital.

Interventions: 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.

Outcomes: 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.

Conclusion: 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.

Figure 1

Prenatal ultrasonography detection indicates a 3 × 3 cm solid, well-defined, hyperechoic mass with uniform internal echo in the fetal right kidney.

Figure 2

Color Doppler ultrasound shows a large nutrient vessel entering the inside of the tumor.

Figure 3

Representative images presenting circular blood flow signal around the tumor.

Figure 4

MRI shows that the posterolateral contour of the right kidney of the fetus is plump, locally convex, and the signals of TIWI, T2-haste and T2-trufi are similar to those of the renal parenchyma. The signals of DWI are slightly higher than those of the renal parenchyma, and the boundary between the lesion and the adjacent structures is clear. DWI = diffusion weighted imaging.

Figure 5

The tumor is adjacent to the renal hilum in the kidney, the cross section of tumor is toughness, solid with grey-white color, and the mass occupies most of renal parenchyma. No clear renal pelvis or calyces are found.

Figure 6

The tumor cells were spindle shaped and fibrous, with light staining of nucleus, rich cytoplasm and acidophilic, occasionally with mitotic image, and the tumor cells grow around tubules and glomerulus.

Figure 7

Actin shows weak positive expression in tumoral cells (magnification, x 200).

Figure 8

SMA shows positive expression in tumoral cells (magnification, x 200).

Figure 9

Vimentin shows positive expression in tumoral cells (magnification, x 200).

Figure 10

CD99 shows positive expression in tumoral cells (magnification, x 200).

Figure 11

Ki-67 shows approximately 5% positive expression in tumoral cells (magnification, x 200).