Pediatric Extra-Renal Nephroblastoma (Wilms' Tumor): A Systematic Case-Based Review

Wilms Tumor (WT) is one of the most common renal tumors in the pediatric population. Occasionally, WT can primarily develop outside the kidneys (Extra-Renal Wilms Tumor, ERWT). Most pediatric ERWTs develop in the abdominal cavity and pelvis, whereas the occurrence of this tumor in other extra-renal sites represents a minor part of ERWT cases. In addition to describing a case of spinal ERWT (associated with spinal dysraphism) in a 4-year boy (to add a further clinical experience on this very rare pediatric tumor), we performed a case-based systematic literature review on pediatric ERWT. We retrieved 72 papers providing enough information on the diagnosis, treatment, and outcomes of 98 ERWT pediatric patients. Our research highlighted that a multimodal approach involving both chemotherapy and radiotherapy, after partial or complete tumor resection in most cases, was typically used, but there is no standardized therapeutic approach for this pediatric malignancy. However, this tumor may be potentially treated with a better success rate if the diagnostic confirmation is not delayed, the mass can be totally resected, and an appropriate and, possibly, tailored multimodal treatment can be promptly established. In this regard, an international agreement on a unique staging system for (pediatric) ERWT is definitely needed, as well as the development of international research, which may be able to gather several children diagnosed with ERWT and, possibly, lead to clinical trials which should also include developing countries.