Gardner syndrome, also known as familial colorectal polyposis, is an autosomal dominant form of polyposis characterized by the presence of multiple polyps in the colon together with tumors outside the colon.The extracolonic tumors may include osteomas of the skull, thyroid cancer, epidermoid cysts, fibromas and sebaceous cysts, as well as the occurrence of desmoid tumors in approximately 15% of affected individuals. The countless polyps in the colon predispose to the development of colon cancer; if the colon is not removed, the chance of colon cancer is considered to be very significant. Polyps may also grow in the stomach, duodenum, spleen, kidneys, liver, mesentery and small bowel. In a small number of cases, polyps have also appeared in the cerebellum. Cancers related to GS commonly appear in the thyroid, liver and kidneys.
At this time, there is no cure, and in its more advanced forms, it is considered a terminal diagnosis with a life expectancy of 35–45 years; treatments are surgery and palliative care, although some chemotherapy has been tried with limited success