Cancer is caused when normal cells in the body become old or damaged, which causes them to divide endlessly and survive when the body does not need them. In some cases, this uncontrolled division of cells can cause tumors (clusters of body tissue formed by these extra cells). However, some cancers (cancers of the blood such as luekemias), do not usually form solid tumors.
When these tumors are able to spread into other tissues in the body, they are called malignant (cancerous). Sometimes these pieces of these malignant tumors will break off from the original cluster, which allows them to travel to other locations (through the blood or other body systems) in the body. Because of its ability to travel, removing the original tumor cluster does not always prevent the tumor from growing back in the same place or in another location.
However, not all tumors are cancerous. Benign (non-cancerous) tumors grow in the same way that malignant (cancerous) tumors grow, but they are not able to spread to other tissues or locations in the body. Therefore, if you remove the tumor, it usually does not grow back.
Please click here for more information about cancer from the National Institutes for Health.
[Credit: National Institutes for Health]