A cancerous cell is a type of mutated cell. Mutated cells can be caused by disruptions in environment, such as high-frequency waves or genetically defined. In cases of cancerous cells, these are the two main causes.
When a cell becomes cancerous, it begins to grow at an uncontrollable rate, multiplying much faster than they would have in their previous state. Most cells are programmed to kill themselves when there is a problem. This is not the case for cancerous cells.