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  • Updated 10.17.2023
  • Released 09.28.1999
  • Expires For CME 10.17.2026

Turcot syndrome



Turcot syndrome is a genetic disorder clinically characterized by primary brain tumors and colorectal adenomas and carcinomas. It has been found to be associated with germline mutations in the adenomatous polyposis coli (APC) gene and hereditary nonpolyposis colorectal cancer (HNPCC), with mutations in mismatch repair genes. This article describes the pathogenesis, clinical features, and diagnosis of this syndrome. The management of patients with Turcot syndrome takes into consideration both the CNS lesions and colorectal lesions, the potential risk for other malignancies, and the ethical aspects and possible consequences of genetic testing. Early detection of brain tumors in patients with familial adenomatous polyposis coli will likely improve outcome.

Key points

• Turcot syndrome is an association of primary brain tumors with familial adenomatous polyposis coli or hereditary nonpolyposis colorectal cancer.

• Turcot syndrome is a genetic disorder associated with germ-line APC mutations, as well as genes that affect DNA mismatch repair (including MLH1, MSH2, MSH6, PMS2, and EPCAM).

• An important differential diagnosis is metastatic brain tumor in cases with colorectal carcinoma.

• Early detection of brain tumors in patients with familial adenomatous polyposis coli and in families with DNA mismatch repair mutations might improve outcome.

• Prognosis in advanced cases is poor, and death is usually due to the malignant brain tumor, but some patients die due to colorectal or other malignancies.

• A better understanding (and classification) of the disease at the genetic level is likely to lead to the most impactful advances in its management.

Historical note and terminology

The first case of polyposis coli associated with a medulloblastoma, as well as thyroid carcinoma, was described in a case report in 1949 (08). Turcot and colleagues described the association of primary malignant tumors of the CNS with adenomatous polyposis coli in two teenaged siblings in 1959 (45). Medulloblastoma involving the spinal cord was found in one sibling and glioblastoma multiforme in the other.

The gene for adenomatous polyposis coli (APC gene) was mapped and cloned in 1991 (15; 31). Hamilton and colleagues explored the molecular basis of Turcot syndrome by looking at 14 families with clinically defined Turcot syndrome as well as the family originally described by Turcot (17). They found germline APC mutations in 10 of the families, where the predominant brain tumor was medulloblastoma. In other families and the original family described by Turcot, germline mutations in the mismatch-repair genes hMLH1 or hPMS2 and replication errors characteristic of hereditary nonpolyposis colorectal cancer (also known as Lynch syndrome) were found.

Definition. Controversy persists regarding whether Turcot syndrome constitutes a distinct genetic disorder, but most agree that it is a clinical syndrome consisting of brain and gastrointestinal malignancies with different underlying genetic etiologies. The earlier cases of Turcot syndrome included only brain tumors of neuroepithelial origin, but some authors have reported other CNS tumors as well. One of the original cases of Turcot syndrome had a 3 mm chromophobe adenoma of the pituitary in addition to glioblastoma. Several other tumors of organs besides the colon and brain have been reported in some cases of Turcot syndrome. It is difficult to define the exact components of this syndrome. The synonym glioma-polyposis complex, sometimes used to describe the syndrome, does not adequately describe it because it restricts the brain tumor to glioma and the colon lesions to polyposis. Many consider Turcot syndrome a variant of familial adenomatous polyposis (apc; commonly associated with medulloblastomas), constitutional mismatch repair deficiency (CMMRD), and Lynch syndrome (more commonly associated with gliomas).

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