The vast majority, over 90 percent, are noncancerous, but could still be intrusive, like Crow surmised.
Old English cancer "spreading sore, cancer" (also canceradl), from Latin cancer "a crab," later, "malignant tumor," from Greek karkinos, which, like the Modern English word, has three meanings: crab, tumor, and the zodiac constellation (late Old English), from PIE root *qarq- "to be hard" (like the shell of a crab); cf. Sanskrit karkatah "crab," karkarah "hard;" and perhaps cognate with PIE root *qar-tu- "hard, strong," source of English hard.
Greek physicians Hippocrates and Galen, among others, noted similarity of crabs to some tumors with swollen veins. Meaning "person born under the zodiac sign of Cancer" is from 1894. The sun being in Cancer at the summer solstice, the constellation had association in Latin writers with the south and with summer heat. Cancer stick "cigarette" is from 1959.
cancer can·cer (kān'sər)
Abbr. CA Any of various malignant neoplasms characterized by the proliferation of anaplastic cells that tend to invade surrounding tissue and metastasize to new body sites.
The pathological condition characterized by such growths.
Our Living Language : The human immune system often fights off stray cancer cells just as it does bacteria and viruses. However, when cancer cells establish themselves in the body with their own blood supply and begin replicating out of control, cancer becomes a threatening neoplasm, or tumor. It takes a minimum of one billion cancer cells for a neoplasm to be detectable by conventional radiology and physical examinations. Cancer, which represents more than 100 separate diseases, destroys tissues and organs through invasive growth in a particular part of the body and by metastasizing to distant tissues and organs through the bloodstream or lymph system. Heredity, lifestyle habits (such as smoking), and a person's exposure to certain viruses, toxic chemicals, and excessive radiation can trigger genetic changes that affect cell growth. The altered genes, or oncogenes, direct cells to multiply abnormally, thereby taking on the aggressive and destructive characteristics of cancer. Treatments such as surgery, chemotherapy, and radiation are effective with many cancers, but they also end up killing healthy cells. Gene therapy attempts to correct the faulty DNA that causes the uncontrolled growth of cancer cells. Researchers are investigating other treatments, such as immunotherapy (the stimulation of the body's natural defenses), vectorization (aiming chemicals specifically at cancer cells), and nanotechnology (targeting cancer cells with minute objects the size of atoms).
A faint constellation in the Northern Hemisphere near Leo and Gemini. Cancer (the Crab) is the fourth sign of the zodiac.
A disease characterized by rapid growth of cells in the body, often in the form of a tumor. Cancer is invasive — that is, it can spread to surrounding tissues. Although this disease is a leading cause of death in the United States, research has provided considerable insight into its many causes (which may include diet, viruses, or environmental factors) and options for treatment (which include radiation, chemotherapy, surgery, and possibly gene therapy).
Note: The term cancer is often used to describe a nonmedical condition that is undesirable, destructive, and invasive: “Watergate was a cancer on the presidency.”