There are over 100 different types of cancer. Each is named by the type of cell that is initially affected. Cancer is a disease in which some of the body’s cells grow uncontrollably and spread to other parts of the body. Cancer harms the body when mutated, or altered cells divide uncontrollably to form lumps or masses of cancerous tissue called tumours. Tumours can be cancerous (malignant) or not cancerous (benign).
Benign tumours stay in one spot and demonstrate limited growth. These are more easily treated than the more dangerous malignant tumours.
Malignant tumours occur when a cancerous cell manages to move throughout the body using the blood or lymphatic systems, destroying healthy tissue in a process called the invasion or if that cell manages to divide and grow, making new blood vessels to feed itself. This process is called angiogenesis.
Metastasis is a process that is caused when a tumour successfully spreads to other parts of the body and grows, invading and destroying other healthy tissues. Metastasised tissue is a serious condition and the most difficult to treat.
Source: National Cancer Institute