Cancer is uncontrolled cellular division. Normally, cells constantly grow and proliferate in an order way to enable us to grow and replace apoptosis cells or damaged cells. When cells grow in an uncontrolled way, a lump called a tumor will formation in your body.
Tumors can be nonmalignant or malignant. The former is not spread outside to other parts of the body, the later develop malignant tumors (cancer).
Malignant tumors are made up of cancer cells. At the beginning of a malignant tumor, it may be confined to someone organ itself, which is called cancer in situ. If these cells are not treated, they may metastasis beyond their normal boundaries and into other surrounding tissues or any other tissues through blood circulation.
In general sense, cancer always refers to all the cancer, but in pathology it is only derived from epithelial tissues and also constitutes a major part of the organs such as the liver. On other sources cancer, we often referred to sarcoma such as osteosarcoma, rhabdomyosarcoma; in addition, there are other common cancers because of non naming rules, such as blood cancer known as leukemia, a lymphatic system cancer called Hodgkin’s disease.