Education Icon

Mesoblastic Nephroma

David Cheng, MD
Faye C Laing, MD

February 20, 1997

Presentation

A newborn girl presented for follow-up examination of a renal mass initially detected on prenatal sonograms.

MR images courtesy of Children's Hospital, Boston

Imaging Findings

Sonograms of the right kidney
T1-weighted coronal MR image of the abdomen
Gadolinium-enhanced T1 coronal MR image

Ultrasound (US) scans demonstrate a 3.4 x 4.0 cm mass located at the lower pole of the right kidney (arrows). The mass is well circumscribed, heterogeneous, and mostly hyperechoic with a few anechoic regions. The upper pole of the right kidney and all of the left kidney (not shown) appear normal. The coronal T1-weighted magnetic resonance (MR) image shows a heterogeneous low-signal mass (white arrow) with a central high signal (black arrows). The mass enhances with gadolinium (arrow).

Differential Diagnosis

Unilateral renal enlargement in a neonate is due most commonly to hydronephrosis or multicystic dysplastic kidney. The differential diagnosis for a solitary renal mass, however, includes mesoblastic nephroma, Wilms tumor, neuroblastoma, multilocular cystic nephroma, and in older children, renal cell carcinoma. Mesoblastic nephroma is the most common benign renal tumor in the neonate, while Wilms tumor is the most common renal malignancy (1).

Diagnosis

Mesoblastic nephroma, confirmed by pathology

Discussion

Congenital mesoblastic nephroma is known by many other names including fetal renal hamartoma, leiomyomatous hamartoma, and mesenchymal hamartoma of infancy. A few cases of mesoblastic nephroma have been reported in older children, and isolated adult cases exist (5). In one series of 20 cases, all were unilateral (2). Some cases are associated with hypertension, skeletal fibromatosis, and neuroblastoma. The tumor is clinically benign.

Imaging Characteristics

A soft tissue mass may be detected on plain abdominal radiographs. Calcification is rare.

Ultrasound usually shows a well circumscribed, hypoechoic mass without posterior acoustic enhancement. Anechoic areas representing cysts may be present. On T1-weighted MR images, a low signal mass that displaces the kidney without caval extension has been described (4).

On intravenous pyelography, a mass 2-7 times the size of the kidney is visible and displays mass effect.

On angiography, sonographically solid areas of the tumor are hypervascular while hypoechoic areas are hypovascular. Contrast material collecting within the tumor is more likely to be within an entrapped calyx rather than within functioning portions of the tumor.

Differential Imaging Diagnosis

Mesoblastic nephroma is histologically similar to, and often radiologically indistinguishable from, Wilms tumor (2). In one series, 50% of Wilms tumors diagnosed in children one year old or less were actually mesoblastic nephroma (3). Congential mesoblastic nephroma can be detected in asymptomatic patients on screening studies, but usually presents as an abdominal mass at a mean age of 3.5 months (4). This pattern is different from Wilms tumor and neuroblastoma, which present at peak ages of 2-3 years.

Neuroblastoma can be distinguished from both Wilms tumor and mesoblastic nephroma because it is extrarenal, tends to displace the kidney, and encases adjacent blood vessels. Calcifications can be seen in over half of all neuroblastomas and in 10-15% of Wilms tumors, but only rarely in mesoblastic nephroma.

Treatment

Surgical resection of congenital mesoblastic nephroma is curative. Adjuvant therapy, such as radiation or chemotherapy, increases morbidity and does not improve the already excellent prognosis (2, 3). Radiation therapy has been reported to cause scoliosis in some patients (3).

References

1. Bisset GS, Strife JL, Kirks DR. Genitourinary tract. In: Kirks D, ed. Practical pediatric imaging: diagnostic radiology of infants and children. Boston: Little, Brown, and Company, 1991:994-1010.

2. Bogdan R, Taylor DEM, Mostofi FK. Leiomyomatous hamartoma of the kidney: A clinical and pathological analysis of 20 cases from the kidney tumor registry. Cancer 1973;31(2):462-467.

3. Bolande RP, Brough JB, Izant RJ. Congenital mesoblastic nephroma of infancy: A report of eight cases and the relationship to Wilms tumor. Pediatrics 1967;40(2):272-278.

4. Rieumont MJ, Whitman GJ. Mesoblastic nephroma. Am J Roentgenol 1994;162:76.

5. Block NL, Grabstald HG, Melamed MR. Congenital mesoblastic nephroma (leiomatous hamartoma): first adult case. J Urol 1973;110:380-383.

Dear Visitors: Nothing on this World Wide Web site should be considered medical advice. Only your own doctor can help you make decisions about your medical care. It is not the policy of the Brigham and Women's Hospital Department of Radiology to provide consultation on the World Wide Web or via e-mail. If you have a specific medical question or are seeking medical care, please call the Brigham and Women's Hospital toll-free physician referral line at 1-800-294-9999.

Is this a mirrored page?
The official homepage of the BrighamRAD Teaching Case Database is http://brighamrad.harvard.edu/education/online/tcd/tcd.html

Contact the BrighamRAD Design Team for additional information about this website.