A tumor (also called neoplasm) is an abnormal mass of cells in the body. It is caused by cells dividing more than normal or not dying when they should. Tumors can be classified as benign or malignant.
Malignant tumors have cells that grow uncontrollably and spread locally and/or to distant sites. Malignant tumors are cancerous (ie, they invade other sites). They spread to distant sites via the bloodstream or the lymphatic system. This spread is called metastasis. Metastasis can occur anywhere in the body and most commonly is found in the liver, lungs, brain, and bone.
Malignant tumors can spread rapidly and require treatment to avoid spread. If they are caught early, treatment is likely to be surgery with possible chemotherapy or radiotherapy. If the cancer has spread, the treatment is likely to be systemic, such as chemotherapy or immunotherapy.
The cancer cells that move to other parts of the body are the same as the original ones, but they have the ability to invade other organs. If lung cancer spreads to the liver, for example, the cancer cells in the liver are still lung cancer cells.
Credit : JAMA Network
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