EXTRARENAL WILMS' TUMOR: A RARE CASE PRESENTATION

Purpose: Wilms' tumor is the most common primary abdominal neoplasm arising in the kidney in the pediatric population. However, Wilms' tumor arising outside of the kidney (extrarenal Wilms' tumor) is a highly rare occurrence. In this report, we present the case of a six-year-old girl who presented with a large midline pelvic and abdominal mass, which after extensive pathologic analysis was diagnosed as Wilms' tumor. To our knowledge, this is one of only a small number of cases reported of Wilms' tumor arising in the pelvis of a child. The purpose of this study is to bring attention to a rare presentation of a common tumor arising in children. Methods: This case was studied to demonstrate an uncommon presentation of a common childhood tumor, allowing the reader to better understand presentations of Wilms' tumor arising outside of the kidney. Literature review of other previous reports of extrarenal Wilms' tumor in children was used to compare and contrast the tumor sites, modes of therapy applied, and overall outcomes. Results: After extensive analysis of imaging and pathologic specimens, the patient was diagnosed with extrarenal Wilms' tumor. The patient was administered extensive chemotherapy prior to surgical removal (neoadjuvant chemotherapy) according to a standard regimen for Wilms' tumor. After responding well to the chemotherapy, the tumor was resected, after which additional chemotherapy was administered. Five years since the completion of treatment, the patient has had no recurrence of malignancy. Conclusions: Due to its rare presentation, along with lack of tumor markers, it can be very difficult to make the diagnosis of extrarenal Wilms' tumor without surgical exploration and careful pathologic analysis. This brings to light the significance of a comprehensive patient history and physical exam. Examination of this case, along with prior reports of extrarenal Wilms' tumor, suggests that when evaluating a child with a solid tumor arising in the abdomen and pelvis, extrarenal Wilms' tumor should be a consideration in the differential diagnosis.