Ectopic nephrogenic rests in children: the clinicosurgical implications.

Introduction/background: Ectopic nephrogenic rests (ENR) are rare. The incidental discovery of these lesions in children has particular clinicosurgical implications, especially given the association between ENR and the development of extrarenal Wilms' tumors (ERWT).

Methodology: We reviewed the hospital records of patients with ERWT and ENR treated at our hospital over a 10-year period to identify those patients with histopathologically confirmed ENR and/or ERWT.

Results: Ninety-five children with Wilms' tumor (WT) were identified, but only 1 case of ENR and ERWT. This patient was a 14-month-old boy who was incidentally found to have a mass in the left inguinal canal during orchiopexy. After histology, a provisional diagnosis of ENR was made. Six months later, the child went on to develop an ERWT at the same site. Periodic postsurgical follow-up has been uneventful.

Discussion And Conclusions: This was the only case of ENR and ERWT in child in a 10-year review of patients with WT at our hospital. Our experience stresses the importance of including ENR in any working differential diagnosis of unexpected masses in the inguinal canal in children and underscores why careful long-term follow-up is mandatory. The reasons for the malignant transformation of ENR into primary ERWT are unknown, but our experience lends support for the theory that ENR are precursor lesions to the development of WT even in ectopic sites. The case also provides an example of the kind of technical difficulties presented by paratesticular masses during laparoscopy.