During cell developmental years the addition of cells helps tissue and organs grow . in adults mitosis replaces cells that have become less functional with age or have been damaged or destroyed by illness or injury. Many cells loose their ability to function worthy being to function abnormally. If body cell loses its ability to control mitosis , an abnormal mass of proliferating cells develops -Neoplasm Neoplasms that are harmless=BENIGN TUMOR(Evan) Neoplasms there cancerous= MALIGNANT TUMOR.