What is a Wilms Tumor?

A Wilms tumor is a malignant tumor on the kidney. This is the most common childhood kidney cancer and forms while the baby is still in the womb. Although the Wilms tumor is the most common kidney cancer in children, it is still rare. It occurs in about eight out of every 1 million live births. The Wilms tumor accounts for about 6-7 percent of all childhood cancer and 75 percent are found in children under age five.

The Wilms tumor comes from immature kidney cells that do not mature but instead, grow out of control. Even so, most Wilms tumors are caught at Stage I or II, meaning the prognosis is very favorable. In fact, 90-93 percent of the children diagnosed with a Wilms tumor survive five years.

The Wilms tumor is generally completely removed through surgery. Usually, the Wilms tumor is easily accessible and is localized to the kidney itself. Once removed, the oncologist may recommend chemotherapy and possibly radiation therapy.

There are two types of Wilms tumors: favorable and unfavorable. A favorable Wilms tumor has well-defined, regular small cell nuclei. In the unfavorable type, the cell nuclei are large and distorted. An unfavorable Wilms tumor is more prone to metastasis, and may be harder to control.

Although the symptoms of a Wilms tumor can be nebulous, there are some things a parent should look for: long-term nausea and vomiting, blood in the urine, loss of appetite and night sweats. If these symptoms persist, parents should insist their pediatrician run a complete battery of tests that include a screening for Wilms tumor such as an MRI or CT scan. If the doctors determine there is a mass on the kidney, it will usually then be biopsied and staged. The staging and histology will largely determine treatment.

The good news about the Wilms tumor is that doctors consider it a curable disease. Cure outcomes have jumped from 80 percent to over 90 percent since 1984.