Purpose or Case Report: Wilm’s tumor (nephroblastoma) is the most common pediatric renal mass, with rare reports of extra-renal Wilm’s tumors which primarily arise elsewhere in the retroperitoneum. We present a small series of patients who have recently been treated at our institution with histologically-proven extra-renal Wilm’s tumors. The first patient is a six year old female who initially presented to an outside hospital with a draining “perianal abscess”, who on subsequent workup was found to have a large infiltrative pelvic mass and multiple pulmonary metastases (image 1). The second patient is a six year old female who initially presented with abrupt onset of right-sided abdominal pain which woke her from sleep, and who was found on imaging to have a large right-sided retroperitoneal hemorrhage originating from a hemorrhagic suprarenal mass (images 2 and 3).

We will review the pertinent imaging and histological findings from these patients, as well as briefly review what has been previously published about this rare rumor.

The imaging features of extra-renal Wilm’s tumor are heterogeneous and not specific, making it important that the radiologist consider this etiology when presented with a retroperitoneal mass in a pediatric patient within the first decade of life.
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