Familial adenomatous polyposis is an inherited condition in which patients develop literally thousands of polyps in the GI tract. Virtually all sufferers will get cancer, usually in their 30s or 40s.
It is caused by a mutation in the tumour supressor gene APC on chromosome 5.
The appearance of the colon is:
Treatment tends to be a colectomy before cancer develops.
As an aside, a variation of FAP called 'Gardners Syndrome' exists. This is FAP plus osteomas, epidermal cysts, fibromas and retinal pigmentation.
So after 2 conditions which are defined by polyps, lets look at one which defines itself by not having polyps - Hereditary Non-Polyposis Colorectal Cancer