Malignant Rhabdoid Tumor of the Kidney Mimicking a Perinephric Abscess in a 3-year-old Child.

Malignant rhabdoid tumor of the kidney (MRTK) is a rare and highly aggressive renal malignancy, accounting for <2% of all renal tumors in children. It often has a nonspecific presentation and is associated with poor survival outcomes. A 3-year-old girl presented with flank pain and fever and was initially diagnosed radiologically as having a perinephric abscess. Intraoperative findings revealed a hemorrhagic renal mass, and radical nephrectomy was performed. Histopathology and immunohistochemistry confirmed MRTK with loss of INI1 expression and lymph node metastasis. The patient received adjuvant multiagent chemotherapy and remains under close oncologic follow-up. MRTK can rarely mimic infective renal pathology. Awareness of this presentation is crucial to avoid diagnostic delay and ensure timely surgical management.