A human tumor usually forms in two to four weeks.

The type of tumor and where the tumor formed in the brain.

The type of cancer may have something to do with why tumors form in bones.

When cancer cells spread outside the blood, a solid tumor may form.

It is not known what causes these tumors to form.

Scientists continue to learn more about how tumors form and grow, providing new ways to attack the disease.

Pictures will be taken of the chest and the area where the tumor formed.

If the balance of cell division and death is disturbed, a tumor may form.

A better understanding of how tumors form and grow could lead to new treatments.

About half of these tumors form in the cerebellum or brain stem.