Imatinib is used to treat certain types of leukemia (cancer that begins in the white blood cells) and other cancers and disorders of the blood cells. Imatinib is also used to treat certain types of gastrointestinal stromal tumors (GIST; a type of tumor that grows in the walls of the digestive passages and may spread to other parts of the body). Imatinib is also used to treat dermatofibrosarcoma protuberans (a tumor that forms under the top layer of skin) when the tumor cannot be removed surgically, has spread to other parts of the body, or has come back after surgery. Imatinib is in a class of medications called kinase inhibitors. It works by blocking the action of the abnormal protein that signals cancer cells to multiply. This helps stop the spread of cancer cells.