The National Cancer Institute says there are two types of tumors, benign and malignant. Benign tumors are not cancer. According to NCI, they often can be removed and, in most cases, they do not come back. Cells in benign tumors do not spread to other parts of the body. As a result, benign tumors are usually not considered life-threatening, though they should certainly be monitored and treated correctly.
Malignant tumors are cancer.
Cells in malignant tumors are abnormal and divide without control or order. These cancer cells can invade and destroy the tissue around them. Cancer cells can also break away from a malignant tumor. Angiogenesis Researchers say one of the most important things required for metastasis to occur is the growth of a new network of blood vessels. This process of forming new blood vessels is called angiogenesis.