An immature, embryonic, or primitive cell. It has a nonspecific appearance with multiple nonspecific activities and functions poorly. See differentiate, dedifferentiate.
In cancer, refers to how mature (developed) the cancer cells are in a tumor. Differentiated tumor cells resemble normal cells and tend to grow and spread at a slower rate than undifferentiated or poorly differentiated tumor cells, which lack the structure and function of normal cells and grow uncontrollably.