Wilms’ tumor, also known as nephroblastoma, is a rare form of kidney cancer that affects young children. About 500 cases are diagnosed each year, generally at two to five years of age. If diagnosed and treated early, up to 95% of Wilms' tumor cases are curable.
The stage is set for Wilms’ tumor in the womb. As kidney cells mature in the fetus, they become specialized and form different regions of the kidney. Some of these cells are still immature at birth and continue to develop over the first three or four years of life. In Wilms’ tumor, however, the cells remain immature and begin to reproduce rapidly, forming a mass that can grow quite large before it produces any symptoms.
The most common and noticeable symptom of Wilms' tumor is a hard lump or mass in the stomach area, easily felt through the skin. Less frequent symptoms include:
Blood in the urine High blood pressure Stomach pain Recurring fever
In many cases, parents are the ones who discover the tumor when it grows large enough to be seen or felt. Imaging techniques such as MRI, CT scans, ultrasound or chest X-rays may be used to confirm the doctor's suspicions, but very few of them are found in early stages when they are smaller.
Other tests may be used to see if the tumor has spread or to determine the best treatment approach.
The process used to find out if cancer has spread outside of the kidney to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment. In addition to the stages, Wilms' tumors are described by their histology.
The histology (how the cells look under a microscope) of the tumor affects the prognosis and the treatment of Wilms' tumor. The histology may be favorable or anaplastic (unfavorable). Tumors with a favorable histology have a better prognosis and respond better to chemotherapy than those with anaplastic histology. Tumor cells that are anaplastic divide rapidly and do not look like the type of cells they came from. Anaplastic tumors are harder to treat with chemotherapy than other Wilms' tumors at the same stage.
The following stages are used for both favorable histology and anaplastic Wilms' tumors:
Stage I: The tumor was completely removed by surgery and all of the following are true:
Stage II: The tumor was completely removed by surgery and no cancer cells were found at the edges of the area where the cancer was removed. Before the tumor was removed, one of the following was true:
Stage III: Cancer remains in the abdomen after surgery and at least one of the following is true:
Stage IV: Cancer has spread through the blood to organs such as the lungs, liver, bone, or brain, or to lymph nodes outside of the abdomen and pelvis.
Stage V and those at high risk of developing Wilms' tumor: Cancer cells are found in both kidneys when the disease is first diagnosed.
Wilms' tumor is usually treated with a combination of surgery and chemotherapy. This disease generally affects only one kidney. The cancerous organ is removed along with the adrenal glands and a small margin of surrounding tissue, in a surgical procedure called a nephrectomy.
If the tumor is very large or has spread to other organs and tissues, chemotherapy or radiation therapy may be used to shrink the tumor before attempting surgery. Radiation is also used as a primary treatment in some advanced cases.
Cancer screening exams are important medical tests done when you’re at risk but don’t have symptoms. They help find cancer at its earliest stage, when the chances for successful treatment are highest. However, there are currently no standardized screening exams for Wilms' tumor.