n WHAT IS METASTASIS? Metastasis refers to the spread of cancer from its original location (primary site) to other parts of the body. Wilms tumors may metastasize, or spread, through the blood system or the lymphatic system (tissues and cells that help to fight infection). The most common site of metastasis is the lungs. Wilms tumors sometimes spread to the liver, other kidney, brain, or bones.
n WHAT IS STAGING? Staging is the process of determining the extent of the disease at the time of diagnosis. The method of treatment proposed for your child will depend upon the stage of the disease at the time of diagnosis. Staging for Wilms tumor is determined by the surgeon when the tumor is removed and by X rays and scans that look for metastatic disease.
The following staging system is recommended by the Renal Dis- ease Committee of the Children’s Oncology Group (COG). It is the major staging system currently used for Wilms tumor. Stage I : The tumor is only in the kidney, and the capsule around the kidney is not broken. There is no me- tastasis. The tumor can be removed by surgery. Stage II : The tumor extends outside the kidney and is pushing against the capsule that surrounds the kidney. The tumor has spread into the blood vessels outside the kidney. No spread can be detected at or beyond the edges of the tumor after surgery. Stage III : The tumor has extended beyond the capsule of the kidney but is only in the abdomen. Any of the following conditions may exist: • The tumor is found in the lymph nodes near the kidney. • The tumor has spilled into the peritoneum (the membrane that lines the walls of the abdomen or belly cavity and encloses organs inside the abdomen) before or during surgery, or by growth into the perito- neal surface. • Parts of the tumor are on the peritoneum. • Tumor cells are on the edges of the tumor after its removal and in the tissue surrounding the area where the tumor had been in the body. • The surgeon is not able to remove the entire tumor because it has spread into the surrounding area and has grown into important body structures that cannot be removed. Only a biopsy (medical test done on removed tissue) can be taken. Stage IV : The tumor has spread beyond the areas described in Stage III (for example, into the lungs, liver, bone, brain, or distant lymph nodes). Stage V : Both kidneys have a tumor. Each kidney is staged according to the above criteria, based on the extent of disease before and after surgery.
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