Identification of Lynch syndrome: How should we proceed in the 21st century?

Hereditary Colorectal Cancer in China: Current Status and Progress

<b><i>Background:</i></b> Hereditary colorectal cancer (CRC) accounts for about 5% of the total incidence of CRC. During the last decades, there have been great advances in the research of hereditary CRC in China. <b><i>Summary:</i></b> This review mainly focuses on advances of the genetic basis, clinicopathological features, diagnosis, chemoprevention and treatment of hereditary CRC in China. <b><i>Key Message:</i></b> Hereditary CRC has a higher risk to initiate the progression towards neoplasia than sporadic CRC. It can be diagnosed by clinical manifestation or the relevant genetic testing so as to guide the clinical treatment to improve the survival rate and survival quality of patients. <b><i>Practical Implications:</i></b> Hereditary CRC includes hereditary nonpolyposis CRC (Lynch syndrome), familial adenomatous polyposis and other rare types such as Peutz-Jeghers syndrome and familial juvenile polyposis. Based on the clinical manifestations and family history, highly suspected cases can be screened for in the general population and the diagnosis ruled out by genetic analysis. Then, chemoprevention, endoscopic intervention or surgery can be selected properly to improve patients' survival and quality of life.

Lynch or not Lynch? Is that always a question?

The familial cancer syndrome referred to as Lynch I and II was renamed hereditary nonpolyposis colorectal cancer (HNPCC) only to revert later to Lynch syndrome (LS). LS is the most frequent human predisposition for the development of colorectal cancer (CRC), and probably also for endometrial and gastric cancers, although it has yet to acquire a consensus name. Its estimated prevalence ranges widely from 2% to 7% of all CRCs due to the fact that tumors from patients with LS are difficult to recognize at both the clinical and molecular level. This review is based on two assumptions. First, all LS patients inherit a predisposition to develop CRC (without polyposis) and/or other tumors from the Lynch spectrum. Second, all LS patients have a germline defect in one of the DNA mismatch repair (MMR) genes. When a somatic second hit inactivates the relevant MMR gene, the consequence is instability of DNA repeat sequences such as microsatellites and the tumors are referred to as having the microsatellite instability (MSI) phenotype. However, some of the inherited predisposition to develop CRC without concurrent polyposis, termed HNPCC, is found in non-LS patients, while not all MSI tumors are from LS cases. LS tumors are therefore at the junction of inherited and MSI cases. We describe here the defining characteristics of LS tumors that differentiate them from inherited non-MSI tumors and from non-inherited MSI tumors.