Malignant tumors are cancerous. Cells in these tumors can invade nearby tissues and spread to other parts of the body. The spread of cancer from one part of the body to another is called metastasis. So cells make up a lot of the body. So it can be that cells that grow in a group. when cells are growing, one cell can get damaged and then it becomes a cell suicide. When a can of cells grow. There maybe ONE cell that is damaged cannot be repaired. That ONE cell can infect all the good cells around it. Which then makes the cells mutate. This then can catch onto tissue in the body and cause damage all around the body. This can be fatal to the system.
These are infected cells that can mutate.
A cell thats in the lungs. A idea concept to an infection of cells.