The presence of a crop, or large number, of polyps (see POLYP). The most important form is familial polyposis coli, a hereditary disease characterised by the presence of large numbers of polypoid tumours in the large bowel. Every child born to an affected parent stands a 50:50 chance of developing the disease. Its importance is that sooner or later one or more of these tumours undergoes cancerous change. If the affected gut is removed surgically before this occurs, and preferably before the age of 20, the results are excellent.