Optimizing the detection of hereditary non-polyposis colorectal cancer: An update

A review on the molecular diagnostics of Lynch syndrome: a central role for the pathology laboratory

Lynch syndrome (LS) is caused by mutations in mismatch repair genes and is characterized by a high cumulative risk for the development of mainly colorectal carcinoma and endometrial carcinoma. Early detection of LS is important since surveillance can reduce morbidity and mortality. However, the diagnosis of LS is complicated by the absence of a pre-morbid phenotype and germline mutation analysis is expensive and time consuming. Therefore it is standard practice to precede germline mutation analysis by a molecular diagnostic work-up of tumours, guided by clinical and pathological criteria, to select patients for germline mutation analysis. In this review we address these molecular analyses, the central role for the pathologist in the selection of patients for germline diagnostics of LS, as well as the molecular basis of LS.

Underutilization of microsatellite instability analysis in colorectal cancer patients at high risk for Lynch syndrome

OBJECTIVE

The revised Bethesda Guidelines were published to improve the efficiency of recognizing Lynch syndrome (LS) by identifying LS-related malignancies that should be analyzed for microsatellite instability (MSI). The aim of this study was to evaluate whether MSI analysis was performed in colorectal cancer patients at risk for LS according to the revised Bethesda Guidelines.

MATERIAL AND METHODS

Patients diagnosed with colorectal cancer in 11 Dutch hospitals in 2005 and 2006 were selected from a regional database. The patients were included in the study if they met any of the following criteria; 1) diagnosed with colorectal cancer <50 years, 2) a second LS-associated tumor prior to the diagnosis of colorectal cancer in 2005/2006, and 3) colorectal cancer <60 years with a tumor displaying mucinous or signet-ring differentiation or medullary growth pattern.

RESULTS

Of 1905 colorectal cancer patients, 169 met at least one of the inclusion criteria. MSI analysis had been performed in 23 (14%) of the 169 tumors. MSI status had been determined in 18 of 80 included patients aged <50 years, in 4 of 70 patients with a second LS-related tumor, and in 3 of 41 patients aged <60 years with high-risk pathology features.

CONCLUSIONS

There is marked underutilization of MSI analysis in patients at risk for LS. As a result LS might be underdiagnosed both in patients with colorectal cancer and in their relatives.