ON THIS PAGE: You will learn about how doctors describe a tumor’s growth or spread. This is called the stage. To see other pages, use the menu on the side of your screen.
Staging is a way of describing where the tumor is located, if or where it has spread, and whether it is affecting other parts of the body. Doctors use diagnostic tests to find out the tumor's stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help predict a child's prognosis, which is the chance of recovery.
There are different stage descriptions for different types of tumors. Wilms tumor is staged based on the results of surgery, analysis of the tumor cells (see the Diagnosis  section), and whether the tumor has spread.
Wilms tumor stage groupings
Stage I. The tumor is found in one kidney and can be completely removed with surgery.
Stage II. Cancer is found in the kidney and in the fat, soft tissue, or blood vessels near the kidney. It may have spread to the renal sinus. The renal sinus is the part of the kidney through which blood and fluid enter and exit the organ. The tumor can be completely removed with surgery.
Stage III. Cancer is found in areas near the kidney and cannot be completely removed with surgery. The tumor may have spread to nearby organs and blood vessels or throughout the abdomen and to nearby lymph nodes. Lymph nodes are tiny, bean-shaped organs that help fight infection. Stage III cancer has not spread outside the abdomen.
Stage IV. Cancer has spread to other more distant organs, such as the lungs, liver, bones, and brain, or lymph nodes outside the abdomen.
Stage V. Cancer cells are in both kidneys at the same time. The tumor in each kidney is staged separately.
Refractory. A refractory tumor is a tumor that does not shrink during or after treatment.
Recurrent. A recurrent tumor is a tumor that has come back after treatment. The tumor may come back in the area where it first started or in another part of the body. If the tumor does return, there will be another round of tests to learn about the extent of the recurrence. These tests and scans are often similar to those done at the time of the original diagnosis .
Source: National Wilms Tumor Study Group  Staging System.
The two most important factors that predict the prognosis of a child with a Wilms tumor are:
What the tumor cells look like under a microscope, called the histology of the tumor. A favorable histology is usually linked to a better prognosis. Tumors with an anaplastic histology are less likely to be successfully treated with chemotherapy and/or radiation therapy and require more aggressive treatment.
The stage of the tumor. In general, a low stage cancer is more likely to be successfully treated than a high stage cancer. This is particularly true for Wilms tumors with an anaplastic histology.
Information about the tumor’s stage will help the doctor recommend a specific treatment plan. The next section in this guide is Treatment Options . Or, use the menu on the side of your screen to choose another section to continue reading this guide.