Tumor cells differ from regular healthy cells in their growth patterns, life cycles and methods of intercellular communication. They vary in size and shape and often exhibit irregular nuclei, which contain disorganized chromosomes. Tumor cells are able to grow undetected by the body's immune system and disable attacking immune cells.
Lynne Eldridge M.D. for About.com explains that normal cells operate with a specific function and are regulated by a strict organizational system that tells them how fast to grow, where to grow and when to stop growing. Tumor cells do not serve a function in the body, even when they correspond to a specific organ and mimic normal cells. Tumor cells multiply at a fast rate without stopping and do not obey the communications system within the body that regulates the behavior of normal cells, notes Eldridge.
Tumor cells lack an outer adhesive coating that normal cells possess, which allows tumor cells to break free from each other and travel to other areas of the body. For this reason, cancer is able to spread from its original tumor site and implant elsewhere in the body and begin multiplying rapidly to form new tumors. According to Eldridge, normal cells pull from the body's blood supply only when it is necessary to repair damaged tissue. However, tumor cells indefinitely exploit blood supplies and build a network of localized blood vessels to consistently fuel their growth.