Nephroblastoma (Wilms tumor) is the most common kidney tumor in children. It is a malignant embryonic tumor with a good prognosis with more than 85% long-term survival with appropriate chemotherapy, surgery (which most often consists of a total nephrectomy) and radiotherapy for locally invasive forms. Some nephroblastomas (approximately 10%) present with vascular extension with vena cava thrombus, a situation which may worsen the prognosis due to the complexity of the surgery. While the oncological treatment of nephroblastoma is highly formalized, to date there is no specific guideline on the surgical management of this rare clinical presentation of nephroblastomas.

The aim of the study is to provide recommendations for the surgical management of nephroblastomas with vena cava thrombus in a large multicenter series.

Nephroblastoma (Wilms tumor) is the most common kidney tumor in children. It is a malignant embryonic tumor with a good prognosis with more than 85% long-term survival with appropriate chemotherapy, surgery (which most often consists of a total nephrectomy) and radiotherapy for locally invasive forms. Some nephroblastomas (approximately 10%) present with vascular extension with vena cava thrombus, a situation which may worsen the prognosis due to the complexity of the surgery. While the oncological treatment of nephroblastoma is highly formalized, to date there is no specific guideline on the surgical management of this rare clinical presentation of nephroblastomas.

The management of children with nephroblastomas with vena cava thrombosis is very specific because of the vital risks to diagnosis, especially pulmonary embolism but also cardiac arrest (in the event of extension in the right atrium) and Cerebrovascular accidents by embolism, rarer. Surgery of the primary tumor and its intravascular extension is complex and may require the use of extracorporeal circulation, a source of significant morbidity and even mortality. These patients who will actually have a single kidney are at high risk for renal failure due to possible contralateral kidney damage during surgery. Surgery is not clearly codified because cases are rare, including in expert centers.

The aim of the study is to provide recommendations for the surgical management of nephroblastomas with vena cava thrombus in a large multicenter series.

Inclusion Criteria:

• Minors with nephroblastoma with vena cava thrombosis +/- atrial extension.
• Cared between 1999 and 2019 in the centers of the study.

Exclusion Criteria:

- Other renal and non-renal tumors with vena cava thrombosis.

Children with nephroblastoma with vena cava thrombosis +/- atrial extension cared between 1999 and 2019 in Parisian hospitals: Necker and Bicêtre.