Horseshoe kidney with teratoid type of Wilms tumor: a rare case report.

Background: Horseshoe kidney is the most common renal fusion anomaly, and Wilms tumor is the most frequent renal malignancy in children. The occurrence of Wilms tumor in association with horseshoe kidney is a scarce anomaly. However, the arising of a teratoid type, which is a rare variant of Wilms tumor in a horseshoe kidney, is exceptionally unique.

Case presentation: This report presents a 5-year-old male admitted with horseshoe kidney involved by a large heterogeneous calcified mass that was diagnose on biopsy as Wilms tumor blastemal dominant. According to the local and regional extension and metastatic tumor in the lungs, the patient underwent neoadjuvant chemotherapy and then surgery. Post-operative pathologic findings confirmed the diagnosis of teratoid Wilms tumor.

Conclusions: The occurrence of renal anomalies associated with a malignancy might be more frequent in the clinical environment. There are numerous differential diagnoses for renal tumors and masses, but the possibility of exceptional anomalies should not be denied, and clinicians should be prepared for these occasions. Although studies propose that chemotherapy has a trivial effect on teratoid Wilms tumors, it is essential to evaluate the tumor for any possibility of regression in non-teratoid regions before proceeding to upfront tumoral resection.