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At a glance

It is a genetically transmitted predisposition with a high risk of developing nonpolyposis colorectal cancers. It is also associated with an increased incidence of endometrial (second most common cancer associated with this syndrome), ovary, gastrointestinal, hepatobiliary and upper urinary tracts, brain, and skin.

Synonyms

Cancer Family Syndrome; Familial Cancer Syndrome; Hereditary Nonpolyposis Colorectal Cancer (HNPCC); Hereditary Nonpolyposis Colorectal Carcinoma.

History

It was first described by Alder Scott Warthin, an American pathologist, in 1913. However, it is only in 1966 that Dr Henry T. Lynch (b. 1928), Professor of Medicine at characterized this medical condition. In his earlier work, he chose to define this entity as “Cancer Family Syndrome.” The term “Lynch Syndrome” was subsequently coined in 1984 by other authors than Dr Lynch himself. Dr Lynch named the condition HNPCC in 1985; however, with later advances in understanding the genetics of the syndrome, Lynch Syndrome was preferred to HNPCC.

Classification

Three major groups of cancers associated with this condition can be recognized by histopathological criteria:

  • Group I: Right-sided poorly differentiated cancers

  • Group II: Right-sided mucinous cancers

  • Group III: Adenocarcinomas presenting high level of intraepithelial lymphocytes infiltration

Incidence

Five percent of the colorectal cancer population. Individuals with a confirmed diagnosis present an 80% lifetime risk for colon cancer. The proximal colon is the most often location for this cancer. The mean age to develop this cancer is 44 years when members of a family meet the Amsterdam criteria (see below). Women carrying the genetic of this medical condition also have an 80% lifetime risk of endometrial cancer. The apparition of the disease is in the fifth decade at the mean age of 46 years. The age of apparition of all other cancers vary between the fifth and sixth decades.

Genetic inheritance

Both clinical forms of HNPCC are autosomal dominant with a penetrance of 85 to 90%. Two DNA mismatch repair genes are closely linked to the disease: hMSH2 gene in chromosome 2p and hMLS1 gene in chromosome 3p. Mutations in these genes account for 90% of all known HNPCC families.

Pathophysiology

Defective DNA mismatch repair leads to accumulation of mutations. The mutation load can be identified as errors in long tandem repeat sequences, which produce microsatellite instability.

Diagnosis

It is a familial history that uses the Amsterdam Criteria to establish the diagnosis. Furthermore, colonic screening examinations and DNA genetic testing are necessary to complete the diagnosis. It is essential to eliminate the possibility of a Familial Adenomatous Polyposis.

The Amsterdam Criteria consists of several needed conditions to confirm the diagnosis of Lynch Syndrome. All of them must be fulfilled to ensure the association with this ...

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