Normally, cells divide to produce more cells only when the body needs them.
Sometimes cells keep dividing and thus creating more cells even when they are not needed. When this happens, a mass of tissue forms. This mass of extra tissue is called a tumor.
Tumors are found in all kinds of tissue, and can be benign or malignant.
Tumors:
Benign: Benign tumors are not cancer
Malignant: Malignant tumors are cancer.
Metastasis: The spread of cancer to other sites or organs in the body through the blood stream or lymphatic system is called metastasis.
Malignant tumors generally can be classified in two categories.
Carcinomas: Common sites of carcinomas