Cancer is a disease of all ages and even though cancer is not a common disease in younger people, cancer is recognized as one of the most imp0l1ant causes of death at any age. In fact, when considering the main death causes in people younger than thirty years, cancer is second only to accidents. Beyond the age of thirty years, the number of deaths from cancer increases upon aging, gradually at first, rising simply later on. Apm1 from cancer causing death, the disease is fem'ed because patients who suffer from cancer are often condemned to a long and painful terminal illness. Based on their frequency of occurrence, cancers are traditionally categorized as either epithelial cancers (approximately 85% of all human cancers) or non-epithelial cancers (approximately 15% of all human cancers). Cancers arising from epithelial cells (i.e. cells lining the body cavities and skin) are called cm'Cinomas (Latin: km'kinos - crab or lobster; oma - swelling), while those arising from non-epithelial cells are further subdivided according to the tissue and cell type from which they originate. Thus, sarcomas are derived from connective tissue or muscle cells (Greek: sarx - meat), while leukemias are derived from hematopoietic cells (Greek: leucos - white; haimablood). Other non-epithelial cancers include the ones deJived fi'Om cells ofthe nervous system and germinal or embryonal cells.