Where the cancer starts is called the primary tumour. Some types of cancer, called leukaemia, start from blood cells. They don't form solid tumours. Instead, the cancer cells build up in the blood and sometimes the bone marrow. For a cancer to start, certain changes take place within the genes of a cell or a group of cells.
pommel horse. n. 1. A piece of gymnastic equipment that consists of a padded, loaf-shaped object with two pommels on top and stands horizontal to the floor, usually on adjustable legs. 2. An athletic event in which the pommel horse is used.
noun, plural horses (especially collectively) horse. 1. a large, solid-hoofed, herbivorous quadruped, Equus caballus, domesticated since prehistoric times, bred in a number of varieties, and used for carrying or pulling loads, for riding, and for racing. 2. a fully mature male animal of this type; stallion.