Cancer is a group of several diseases that start in cells, the basic unit of the body. The body is made up of several types of cells, which grow and divide to produce new tissues, in an orderly process, which helps to keep the body healthy.

The growth of the cancer cell is different from the growth of a normal cell.
Instead of dying, the cancer cells continue to grow and form new abnormal cells.

The different types of cancer correspond to the various types of cells in the body. Other characteristics that differentiate the different types of cancer from each other are the speed of cell multiplication and the ability to invade neighboring or distant tissues and organs (metastases).

When the cancer spreads (metastasized), the cells are often found in the lymph nodes and this means that the cancer cells can spread to other organs, such as the liver, bones or brain. When the cancer spreads from its original location to another part of the body, the new tumor has the same type of abnormal cells and the same name as the primary tumor.

The most common form of childhood cancer is leukemia. Other cancers often found in children are brain tumors, lymphomas, Hodgkin's disease, Wilms' tumor, neuroblastoma, osteosarcoma, Ewing's sarcoma, retinoblastomas, rhabdomyosarcoma and hepatoblastomas.