Orphanet rare-disease nomenclature identifier Orphanet_99817 (Non-polyposis Turcot syndrome) or Turcot syndrome type 1 (TS1) is a form of hereditary nonpolyposis colon cancer (HNPCC; see this term) characterized by concurrent presentation of a primary tumor of the central nervous system (principally glial tumors; see this term), relatively few colonic polyps, and adenomas or colorectal carcinoma.