cancer is a form into groups of diseases in which cells are aggressive (grow and divide without respect to normal limits), invasive (invade and break up marching tissues), and metastatic (spread to other locations in the body).

These three malignant properties of cancers differentiate them from benign tumors, which are self-limited in their growth and don't invade or metastasize (although some benign tumor types are capable of becoming unfavorable).

Cancer may affect people at all ages, even fetuses, but risk as antidote to the more common varieties tends to increase with age. Cancer causes about 13% of all deaths. According to the American Cancer Society, 7.6 million people died from cancer in the world during 2007. Apart from humans, forms of cancer may affect other animals and plants. Nearly all cancers are caused by abnormalities in the genetic material of the transformed cells.

These abnormalities may be owing to the personal estate of carcinogens, such as tobacco smoke, radiation, chemicals, or infectious agents. Other cancer-promoting genetic abnormalities may be randomly acquired through errors in DNA replication, or are inherited, and thus present in every part of cells from birth.

Complex interactions between carcinogens and the host genome may explain why only some develop cancer after exposure to a known carcinogen. New aspects of the genetics of cancer pathogenesis, such as DNA methylation, and microRNAs are increasingly being recognized as weighty.