Use of Pretherapy Core Biopsy in the Diagnosis of Pediatric Renal Tumors

BACKGROUND: Pretreatment core biopsy of pediatric renal tumors has been advocated by United Kingdom Children's Cancer Study Group to circumvent the disadvantage of International Society of Paediatric Oncology protocol, where neoadjuvant chemotherapy initiated without histopathological confirmation can result in over- or under-treatment. AIM: This study aims (a) to assess if pretherapy core biopsy correlates with the nephrectomy biopsy; (b) to assess if neoadjuvant chemotherapy changes Wilms tumor (WT) histology, and (c) to assess the incidence of biopsy site recurrence. MATERIALS AND METHODS: Seventy-six children from 2005 to 2016 with renal tumors who underwent a pretherapy core biopsy were included in the study. The biopsy was performed through the posterior flank post-ultrasound marking of the renal mass, by administering intravenous anesthesia. RESULTS: Of the 62 children with WT, an accurate diagnosis was possible in 61. Accurate prediction of anaplasia was possible only in 25%. Reduction in blastemal elements was seen in 26 patients with 10 of them showing completely necrotic tumor. Eleven of the 14 children with non-WT were accurately diagnosed. Core biopsy corroborated with the nephrectomy biopsy in all but 4 patients. Two specimens were inadequate and two cases of congenital mesoblastic nephroma were inaccurately diagnosed, one as spindle cell neoplasm and the other as WT. Biopsy site recurrence was seen in 1 child. CONCLUSION: Pretreatment posterior flank core biopsy in the diagnosis of pediatric renal tumors is safe, simple, and cost-effective with minimal complications.