Cancer develops when a group of many related diseases that begin as cells in a part of the body and begin to grow out of control. Although there are many different kinds of cancer, they all begin because of out-of-control growth of abnormal cells.
Our body is form by much different type of cells. Under normal circumstances, cells grow and divide to produce more cells as the body requires them. This systematic process helps to keep that body healthy. However, sometimes the cells keep dividing when new cells are not required. Over time, these extra cells form a mass of tissue. This growth is known as tumors. Tumors can be benign or malignant.
Benign tumors are not cancerous. They usually can be removed, and in most cases, they will never grow back. Cells from benign tumors do not spread to other parts of the body or organs. Therefore, benign tumors have no threat to life.
Malignant tumors are cancerous. The cells found in these tumors are abnormal. The can divide without control or order, and they can overrun and damage nearby tissues and organs. Cancerous cells can break away from a malignant tumor and enter the bloodstream or the lymphatic system. Here is where the cancerous cells will travel and spread from the original (primary) cancer site to form new tumors in other parts of the body and organs such as the colon, stomach, throat, ovary, breasts, or lung. This spread of cancer is known as metastasis.
Not all of cancerous cells form tumors. Leukemia and lymphoma are cancer that arises from blood-forming cells. The abnormal cells circulate in the bloodstream and lymphatic system. They may too invade (infiltrate) body organs and form tumors.