1) Monthly journal 
Cancer cells are cells that grow and divide at an unregulated, quickened pace. Although cancer cells can be quite common in a person they are only malignant when the other cells (particularly natural killer cells) fail to recognize and/or destroy them. In the past a common belief was that cancer cells failed to be recognized and destroyed because ...
A cell that divides and reproduces abnormally with uncontrolled growth. This cell can break away and travel to other parts of the body and set up another site, referred to as metastasis. ... (09 Oct 1997) ... 
[n] - a cell that is part of a malignant tumor
noun a cell that is part of a malignant tumor
a cell that divides and multiplies uncontrollably and has the potential to spread throughout the body, crowding out normal cells and tissue.