The Rare Association of Spina Bifida and Extrarenal Wilms Tumor: A Case Report and Review of the Literature

BACKGROUND: The diagnosis of nephroblastoma outside of the kidneys, in the absence of a renal primary tumor, is known as extrarenal Wilms tumor (ERWT). ERWT is an uncommon entity that typically involves the embryonic path of the developing kidneys and gonads. The occurrence of ERWT in a dysraphic spine is uncommon, with no reported cases of preoperative diagnosis, with all cases diagnosed at pathology. These tumors are malignant and ideally should be completely excised. Thus, preoperative diagnosis would be highly desirable. CASE DESCRIPTION: A newborn female was found to have a lumbar lipoma. Magnetic resonance imaging (MRI) was performed to rule out lipomyelomeningocele. The MRI showed a dorsal lipoma on the terminal spinal cord, as well as a 2 x 2 cm uniformly enhancing mass abutting the bifid posterior elements of L5. The lesion was completely excised, and the pathological diagnosis was ERWT. We report this case with a review of the literature to raise awareness of this association, illustrate the key imaging findings, and document the clinical outcome. - CONCLUSIONS: The lack of pathognomonic radiologic features makes the preoperative diagnosis extremely difficult, but a diagnosis of ERWT should be considered in the context of a soft tissue mass without the typical imaging features of a hemangioma or teratoma.