Normal body cells are made up of organelles and a nucleus that contains the chromatin, which is a combination of DNA and proteins that make up a chromosome. This nucleus also contains a nucleolus, a small structure with RNA that plays an important part in protein synthesis. Under normal circumstances, cells of the same type are somewhat equal in size, have a common shape and spread out evenly. The cells grow slowly by a process known as mitosis, adhere (stick) to each other and spread out in a layer formation to collectively form a tissue.

Benign tumors also have normal cells and grow in an ordered manner. However a benign tumor has no physiological function and is therefore considered as an unnecessary growth in the body.

A malignant tumor does not have normal cells. These ‘cancer’ cells are different from normal cells in the following ways :
* Irregular size of cell and nucleus.
* Irregular shape of cell and nucleus.
* Malignant cells stain differently from normal cells under microscopic examination.
* Chromatin within nuclei clump irregularly.
* Nuceloli are large, prominent and irregular.
* Malignant cells do not stick (adhere) to each other as well as normal cells.
* Malignant cells are compacted within a smaller area.

It is the abnormal genetic material in a malignant cell that is responsible for carcinogenesis (the process of malignancy). This genetic material causes the cells to behave, multiply and grow in the manner that is referred to as a malignancy.