Humans are made up of cells. Within the cell are genes which direct and control all the cell's functions and determine how and when it divides and grows. Normal cells divide and grow at a controlled rate. How fast or slow a cell divides and grows, and what function it does, depends on the gene within that cell. Cancer begins as a change in the gene of a single normal cell in any part of the body. Once this change takes place, the set of instructions in the gene is changed and the cell no longer acts like it normally does. "Cancer" is actually due to the accumulation of many such errors.
Other than the word cancer, several other terms are sometimes used to describe the type of cancer that arises from different tissues in the body.
Tumour - lump or growth usually from the primary or original site.
Neoplasia - commonly known as cancer.
Carcinoma - cancer that originates from epithelial tissues.
Sarcoma - cancer that originates from connective tissues such as muscles.
Leukaemia and Lymphoma - cancers that arise from blood and lymphatic cells.
A malignant tumour has the ability to spread from its original site into surrounding tissues and to other parts of the body. When that happens, the area where the cancer has invaded will have the same kind of abnormal cell and the same name as the original cancer. For example, if lung cancer spreads to the liver, the cancer cells in the liver are still lung cancer cells. This condition is called metastatic lung cancer. It is not liver cancer.
A benign (non-cancerous) tumour does not spread or invade other parts of the body.
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