Wilms tumor with intravascular tumor thrombus.

Wilms tumor (WT) is one of the most common solid tumors in children. It is the second most common extracranial solid tumor after neuroblastoma. WT has a strong tendency to invade blood vessels in the form of tumor thrombus, into the renal veins, and inferior vena cava and even into the right atrium. Extension of tumor thrombus along to the renal vein into the inferior vena cava occurs in 4-10% of all patients. Tumor thrombus extending to the right atrium is less reported as 0.7-1%. WT with renal vein thrombus has been reported to be more common in the right kidney because of the shorter right renal vein. Most patients with tumor thrombus are asymptomatic and diagnosis is only made on imaging investigations. Several imaging modalities including computed tomography (CT), magnetic resonance imaging (MRI) and Doppler ultrasonography (USG) can demonstrate intravascular tumor thrombus before surgery. In addition to CT and MRI, Doppler USG is reliable in demonstrating the presence and extent of inferior vena cava tumor thrombus. The management of WT with tumor thrombus is determined by multiple factors such as extent of tumor thrombus, chemotherapy response of the tumor. Now, it is generally recommended to use preoperative chemotherapy to a patient presenting with intravascular tumor thrombus. This approach is helpful to decrease the extent of the vascular thrombus which facilitates surgical excision. Most intracaval and intraatrial thrombi in WT show a response to chemotherapy. Neoadjuvant chemotherapy causes tumor regression in nearly half of the patients. Most of them can be managed without the need for cardiac bypass surgery. The decision of initial surgery or preoperative chemotherapy should be carefully determined on every case. Primary surgery would only be indicated in a patient who is unstable because of thrombus that might dislodge and cause acute symptoms. Presence of tumor thrombus in WT needs for multidisciplinary care including pediatric oncologists, pediatric surgeons, and pediatric cardiac surgeons.