Stages of Wilms Tumor and Other Childhood Kidney Tumors
There are three ways that cancer spreads in the body.
The three ways that cancer spreads in the body are:
- Through tissue. Cancer invades the surrounding normal tissue.
- Through the lymph system. Cancer invades the lymph system and travels through the lymph vessels to other places in the body.
- Through the blood. Cancer invades the veins and capillaries and travels through the blood to other places in the body.
When cancer cells break away from the primary (original) tumor and travel through the lymph or blood to other places in the body, another (secondary) tumor may form. This process is called metastasis. The secondary (metastatic) tumor is the same type of cancer as the primary tumor. For example, if breast cancer spreads to the bones, the cancer cells in the bones are actually breast cancer cells. The disease is metastatic breast cancer, not bone cancer.
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:
In stage I, the tumor was completely removed by surgery and all of the following are true:
- Cancer was found only in the kidney and did not spread to blood vessels of the kidney.
- The outer layer of the kidney did not break open.
- The tumor did not break open.
- A biopsy of the tumor was not done.
- No cancer cells were found at the edges of the area where the tumor was removed.
In 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:
- Cancer had spread out of the kidney to nearby soft tissue.
- Cancer had spread to blood vessels of the kidney.