How are tumors:
The bench consists of many types of cells. Normally, cells grow and divide , and produce more cells as needed to keep the body healthy and functioning properly . Sometimes , however , the process goes wrong - cells become abnormal and form more cells in an uncontrolled manner . These extra cells form a mass of tissue called a growth or tumor. Tumors can be benign , meaning not cancerous, or malignant , which means cancerous.