Cystic nephroma with renal vein thrombus in a child with DICER1 mutation: A case report

Venous tumor thrombus is a known manifestation of Wilms' tumors in a minority of cases but has not been previously described in association with cystic nephroma. We report an original case of a histologically-benign cystic nephroma presenting with venous tumor thrombus extending to the inferior vena cava. The tumor thrombus was not detected by preoperative Doppler ultrasound. The patient was successfully treated with radical nephrectomy, tumor thrombectomy, and IVC closure. Postoperatively, the patient underwent genetic testing which revealed a DICER1 mutation—known to predispose affected individuals to a variety of benign and malignant tumors—and requires intensive surveillance for associated conditions.