Nephroblastoma is a tumor known as an embryonic tumor because the tumor cells resemble cells present during kidney development. It is very different from the kidney cancers seen in adults and requires specific pediatric treatments.

In France, approximately 100 children are diagnosed with this condition each year. The tumor typically appears between the ages of 1 and 5, but it can be diagnosed earlier, in older children, and, in rare cases, in adults.

In the vast majority of cases, no specific cause is identified. There is no proven link to diet, the child’s lifestyle, upbringing, or any psychological event. Parents are not responsible for the onset of the disease.

Most often, nephroblastoma is sporadic, meaning it occurs without any other cases in the family. Familial forms do exist, but they are rare. Certain situations are associated with a genetic predisposition or congenital anomalies, including asymmetric body growth—now referred to as lateralized hyperplasia—aniridia, or certain genitourinary anomalies.

Nephroblastoma is often discovered when the child is in good general health. The most common symptom is an abdominal mass, which is sometimes noticed by the parents while bathing or dressing the child, or by the doctor during an examination.

Imaging

An abdominal ultrasound is often the first test performed. It determines whether the mass originates in the kidney and examines the opposite kidney. A CT scan or MRI of the abdomen then evaluates the tumor, its relationship to neighboring organs, lymph nodes, and blood vessels—particularly the renal vein and the inferior vena cava.

A CT scan of the chest looks for lung metastases, which are the most common site of metastasis. The liver and other abdominal structures are also examined. The tests are selected and organized to obtain the necessary information while minimizing unnecessary testing.

Laboratory Tests

Blood and urine tests assess, among other things, kidney function, the child’s overall condition, and certain differential diagnoses. These tests alone are not sufficient to confirm or rule out a nephroblastoma.

A biopsy is not routinely performed

When a kidney tumor exhibits the typical characteristics of a nephroblastoma, treatment generally begins with preoperative chemotherapy without a biopsy. A biopsy may be considered when the child’s age, imaging findings, or clinical presentation raise suspicion of another type of kidney tumor and the results would alter the treatment strategy.

The treatment strategy is determined during a multidisciplinary pediatric team meeting. It takes into account the patient’s age, whether the tumor is unilateral or bilateral, its extent, the response to initial treatment, the stage determined after surgery, and the anatomopathological characteristics of the tumor.

Chemotherapy Before Surgery

In European treatment protocols, treatment most often begins with chemotherapy. Its purpose is to reduce tumor volume, facilitate the surgical procedure, and decrease the risk of tumor rupture during surgery. The duration of treatment and the drugs used depend on the extent of the disease and the condition of the kidneys.

Surgery

For a tumor confined to a single kidney, the procedure most often involves removing the affected kidney along with the tumor, as well as removing lymph nodes to determine the stage. The remaining kidney can generally maintain normal kidney function. When a tumor affects both kidneys or in certain high-risk situations, the medical team strives as much as possible to preserve kidney tissue through conservative surgery.

A comprehensive analysis of the surgical specimen confirms the diagnosis, assesses the response to chemotherapy, looks for signs of anaplasia or other risk factors, and determines the local stage. These factors determine the course of further treatment.

Treatment After Surgery

Postoperative chemotherapy is recommended in most cases. Its intensity and duration are tailored to the stage and histological subtype. Radiation therapy is not routinely administered. It may be indicated for the abdominal region or certain metastatic sites depending on the stage, histology, possible tumor rupture, and response to chemotherapy.

When both kidneys are affected, preoperative chemotherapy is extended and reevaluated using imaging. Surgery is planned to remove the tumors while preserving as much healthy kidney tissue as possible. This situation requires coordinated expertise in surgery, oncology, radiology, and genetics.

Other pediatric renal tumors, such as rhabdoid tumors, clear cell sarcomas, mesoblastic nephromas, or certain renal carcinomas, are much rarer and require different treatments. Expert pathological analysis is therefore essential.

Follow-up is designed to detect any recurrence and monitor the health of the remaining kidney as well as the long-term effects of treatment. The frequency and type of tests depend on the stage of the disease, the histological subtype, the treatments received, and the time elapsed since the end of treatment. They may include a clinical examination, blood pressure measurement, abdominal and chest imaging, and blood and urine tests.

A recurrence may be localized or occur in another part of the body, most commonly the lungs. The treatment strategy depends on the site of the recurrence, how long after treatment it occurs, the characteristics of the tumor, and the treatments already received. It may combine chemotherapy, surgery, radiation therapy, and, in some cases, participation in a clinical trial.

The Department of Pediatric and Adolescent Oncology coordinates patient care with the imaging, pediatric surgery, pathology, radiation oncology, genetics, nephrology, and supportive care teams. The patient’s case is discussed during a multidisciplinary pediatric team meeting.

The care plan may include psychological support, pain management, nutrition, adapted physical activity, continued schooling, social support, information on fertility preservation, and long-term follow-up. The patient’s needs are reassessed throughout the course of treatment.

The research aims to better identify at-risk groups, tailor the intensity of treatment, preserve kidney function in bilateral cases, and improve the management of high-risk cases or relapses. Open-label trials are evolving and must be presented on the website in a dynamic module linked to the institutional database.