Wilms tumor is a type of kidney cancer that occurs in children. 

Generally, the prognosis for children with Wilms' tumor is very good. Currently, the great majority of children with Wilms' tumor are cured.  Presently, nine out of ten children diagnosed with Wilms' tumor will be alive five years after diagnosis.  This is due to improved surgical techniques, the use of combinations of drugs, and sometimes radiation treatments.

The overall five-year survival rate for children with Wilms tumor is approximately 90%.  That means that 9 out of 10 children with Wilms tumor will live at least five years after their cancer is diagnosed.  The five-year survival mark is the point at which a patient is considered "cured" since these tumors almost never recur later.

There are two major types of Wilms' tumors. These are identified based upon the types of cells that are found (histology) and impact the outcome.  After the tumor or a portion of the tumor is removed, a pathologist will look at the cells that make up the tumor to identify the type of cells that make up the tumor. 

Wilms' tumor of favorable histology

Favorable histology means there is no anaplasia (explained below), and that the chance of a cure is excellent. About 92% of Wilms' tumors have favorable histology.

Wilms' tumor of unfavorable histology

If a tumor has unfavorable histology, it means that the cells are more abnormal or bizarre appearing, and that the nuclei of the cancer cells (the part that contains the cells' DNA) are very large and distorted. This is called anaplasia. Anaplasia is predictive of a pooer chance of cure.