Turcot syndrome: A genetic disease characterized by polyps in the colon (large intestine) in addition to tumors in the brain. The polyps in the colon tend to become malignant. The brain tumors are also malignant. There are sometimes also skin abnormalities including cafe-au-lait (coffee-with-milk) spots, multiple lipomas (fatty tumors), and multiple scalp basal cell carcinoma (skin cancers of the scalp).

Turcot syndrome is inherited in an autosomal recessive manner with both parents carrying a Turcot gene and a 1 in 4 risk for each of their boys and girls of receiving both parental Turcot genes and suffering from the syndrome.

Turcot syndrome can result from mutations in either the adenomatous polyposis coli (APC) gene or the mismatch repair genes underlying the syndrome of hereditary nonpolyposis colon cancer (HNPCC). The type of brain tumor tends to differ, depending on the type of mutation. APC mutations are more commonly associated with medulloblastoma while mismatch repair mutations are more commonly associated with glioblastoma.

Turcot, a French Canadian, pronounced his name with a silent terminal "t." See also: Hereditary nonpolyposis colon cancer.