Renal malignant tumor with the loss of INI1 expression and WT1 positive in a 3-year-old boy: a case report.

Wilms' tumor is the most common primary renal malignancy in children (80%) and the less common tumors include renal cell carcinoma, rhabdoid tumor, clear cell sarcoma, cellular congenital mesoblastic nephroma and medullary carcinoma, all of which originate from renal parenchyma. The tumors originating from renal pelvis are rare. The immunohistochemistry (IHC) showed INI1 deletion with the WT1 positive which has not been reported as we know. A 3-year-old boy was admitted to hospital for vomiting. An ultrasonography examination revealed a mass in the right kidney, medium echo, as well as hydronephrosis with collecting system separation of 3.5 cm. The computed tomography and the magnetic resonance (MR) radical showed that the tumor occupied the right renal pelvis and extended into the ureter. A radical nephroureterectomy was accomplished through a transabdominal approach. The pathologic diagnosis was malignant renal tumor with INI1 deficiency which was atypical in morphology and immunophenotype, but according to immunophenotype renal rhabdomyoid tumor could not be excluded. The patient was treated with carboplatin, etoposide and cyclophosphamide chemotherapy for 6 months. Follow-up studies of the patient showed no indication of recurrence or metastasis 22 months after nephrectomy. The novel findings may expand the spectrum of pediatric renal tumors to include the special malignancy.