Mesoblastic nephroma

Case contributed by Hisham Alwakkaa


Patient presents with growing abdominal mass. His past medical history is significant for Langerhans cell histiocytosis diagnosed after birth.

Patient Data

Age: 6 months
Gender: Male

Images from Ultrasound of the left upper abdomen/left flank


There is a large heterogeneous solid/cystic mass in the left abdomen. There are many small necrotic areas within the center of the mass. There are multiple cystic structures at the inferior aspect of the mass may represent displaced and distorted renal calyces. Displacement of the surroundings organs/vasculature is noted. However, no obvious invasion. On Doppler images, there is a peripheral vascularity in the solid portion. 


There is an extremely large mass occupying most of the left abdomen. It is predominantly cystic in nature centrally with solid well-defined peripheral margins. A small part of the normal left kidney is noted displaced inferiorly. The enhancing renal tissue appears to embrace the adjacent portion of the mass forming acute angles with it, giving the appearance of claw sign. The mass displaces the surrounding organs/vasculature but no convincing evidence of vascular engulfing/ invasion.

Differential diagnosis: Mesoblastic nephroma or Wilms tumor.

Case Discussion

This is a case of a pathology-confirmed congenital mesoblastic nephroma of mixed subtype. diagnosed at the age of six months. In our case, the imaging features could not help with the differentiating between the Wilms tumor and mesoblastic nephroma, but because of the patient age Wilms tumor was less likely.

Summary of the surgical report:

Left kidney mass weighing 730 g excised completely. The mass was well encapsulated with smooth borders. Capsule not violated during dissection. Dense adhesions into the posterior and superior borders of the retroperitoneum.

Summary of the pathology report:

Congenital mesoblastic nephroma of mixed subtype.  Although most of the neoplasm corresponds to cellular morphology, focal areas with the classical component are noted. Focal penetration of the renal capsule with extension into the perinephric soft tissue is noted supporting a local stage of II. Surgical margins and submitted lymph nodes are free of neoplasm, and no nephrogenic rests are appreciated.

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