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.
Horses vs. Ponies. Size is a factor differentiating horses and ponies; the maximum height for ponies is 14.2 hands, and for miniature horses it's 8.5 hands. However, miniature horses are specifically bred to look exactly like their larger namesake, whereas a pony need not resemble a specific breed. Several distinct pony breeds exist, including the Shetland -- the strongest pony of its size -- and the Chincoteague.