Wilms tumor (WT) is the most common malignant renal tumor in children. This study investigated the clinical features, pathological findings, and outcomes of children with malignant renal tumors in Southern Iran. Factors associated with recurrence and mortality were assessed.

Electronic files of children with malignant renal tumors from 2009 to 2023 were reviewed. The 5-year overall survival (OS) and event-free survival (EFS) were reported.

Eighty-three patients (44 males) with a median age of 40 months (range: 3-122) were included. WT was the most common pathological variant (94%). Anaplasia was found in 17.3% of patients. Upfront chemotherapy followed by nephrectomy was performed in 54.2% of the patients. Ten patients (12%) experienced relapse, and five patients (6%) died during the 14-year follow-up. The 5-year OS and EFS were 90.75% (95% CI, 78.64–96.16%) and 81.9% (95% CI, 70.10-89.38%), respectively, and were comparable between the two treatment strategies (upfront chemotherapy vs. upfront nephrectomy). Metastasis and residual disease were associated with relapse, whereas tumor recurrence was the only predictive factor of survival.

WT is a curable disease with excellent outcomes if diagnosed and treated promptly. The timing of nephrectomy does not affect OS and EFS. Patients with low-stage tumors and those with complete surgical excision are at a lower risk of tumor recurrence. Relapse is the primary risk factor for death.