11 month old Rottweiler

Discussion

Nephroblastomas are remainders of renal tissue. They occur between T10-L2 and are intradural-extramedullary. This may be difficult to determine on myelography and MR if the tumor is subpial, and it may appear intradural. MR is better than myelography at distinguishing between these locations. Signs of an intradural-extramedullary tumor include widening of the subarachnoid space and outward displacement of epidural fat, which were not visible in this case. Another reported sign in people is a T1 hypointense band between the mass and the spinal cord which may represent tumor capsule and trapped CSF.
On MR nephroblastomas arise peripherally and compress the cord. They are lobular and may infiltrate. This mass had infiltrated the cord at surgery.
Intradural-extramedullary masses in the spinal cord of dogs have been reported as nephroblastoma, ependymoma, medulloepithelioma, neuroepithelioma, embryonal nephroma, embryonal adenosarcoma, renal adenocarcinoma and Wilms tumor. In Jubb and Kennedy, these are presumed to all arise from embryonal renal tissue, as supported by immunohistochemical staining.