What is cancer? Cancer is a renegade system of growth that originates within a patient's biosystem, more commonly known as the human body. There are many different types of cancers, but all share one hallmark characteristic: unchecked growth that progresses toward limitless expansion. It is difficult to imagine anyone who has not heard of this illness. Most people have been affected because either they or their loved ones or friends are cancer survivors. Because cancer is so prevalent, people have many questions about its biology, detection, diagnosis, possible causes, and strategies for prevention. Cancer is the Latin word for crab. The ancients used the word to mean a malignancy, doubtless because of the crab-like tenacity a malignant tumor sometimes seems to show in grasping the tissues it invades. Cancer may also be called malignancy, a malignant tumor, or a neoplasm (literally, a new growth). source 1:Cancer definition - Cancer Information (Cancers, Symptoms, Treatment) on MedicineNet.com source 2:Comprehensive Cancer Information - National Cancer Institute