Proliferation and programmed cell death are totally in balance to ensure the veracity of organs and tissues. But some times some type of mutations occur in the DNA of the cell, which results imbalance in proliferation and programmed cell death. This may cause uncontrolled and rapid division of cells, which lead to benign tumor initially but some times it may turn in to a malignant tumor and hence CANCER. The benign tumors do not attack and spread to other body organs or tissues but they are harmful only when their target is any vital organ of the body. While malignant tumors are life takers as they can spread and even attack other organs.
How a malignant tumor develops
Tumors act as the self-regulating target of natural selection. Mutated cells promote their own growth and proliferation. Mutations may cause rapid growth, ability to migrate and capacity to spout into blood vessels. If these mutant strains come to dominate the clone the tumor may progress towards a malignant status. Invasive and proliferation abilities of the normal cells are similar to that of cancer cells. But the regulatory mechanisms of normal cells are different from the cancer cells. Hence in the cancer cells mutations mainly affect the regulatory genes of the cells. Rapidly dividing cells provide an opening for cancer. Cancer cells even becomes resistance to the anti cancer pharmaceuticals. The more rapidly the cells divide, the more likely that a variant will amplify into a clone. That is why skin and blood cancers are more common than the bone cancer.