What Is Wilms Tumor?

Wilms tumor, also known as nephroblastoma, is a rare type of kidney cancer that primarily affects young children, usually between the ages of two and five. It is named after the German surgeon Max Wilms, who first described it more than a century ago. Unlike most adult kidney cancers, Wilms tumor develops from immature kidney cells that fail to mature properly during early growth.

Although Wilms tumor is uncommon, it is the most frequent kidney cancer in children. It usually affects only one kidney, but in about 5 to 10 percent of cases, it can appear in both. The cause is not completely understood, but doctors know that it often involves genetic mutations that occur during fetal development. Some children are born with inherited syndromes that increase the risk, such as WAGR syndrome, Denys–Drash syndrome, and Beckwith–Wiedemann syndrome. However, most cases happen by chance with no family history of cancer.

The good news is that Wilms tumor is highly curable, especially when diagnosed early. More than nine out of ten children with this condition survive long term thanks to advances in modern medicine.

The symptoms of Wilms tumor can vary, but the most common sign is a firm lump or swelling in the abdomen, often noticed by a parent or during a routine checkup. Other symptoms may include abdominal pain, blood in the urine, fever, nausea, loss of appetite, or unexplained weight loss. Because these signs can overlap with other childhood conditions, medical assessment is important for an accurate diagnosis.

Diagnosis usually involves ultrasound, CT scan, or MRI to determine the size and extent of the tumor. Blood and urine tests help assess kidney function, and a biopsy confirms the diagnosis under a microscope. Once confirmed, doctors assign a stage based on whether the tumor is confined to the kidney or has spread to nearby lymph nodes, lungs, or liver.

Treatment for Wilms tumor often combines surgery, chemotherapy, and sometimes radiation therapy. The main goal is to remove the tumor while preserving as much kidney function as possible. Children with tumors in both kidneys may undergo partial surgery on each side to retain healthy tissue. Follow-up care includes regular scans to ensure the cancer does not return.

Wilms tumor is one of the greatest success stories in pediatric oncology. With prompt diagnosis and appropriate treatment, most children go on to live normal, healthy lives.

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