Hereditary nonpolyposis colorectal cancer: Identification of novel germline mutations in two kindreds not fulfilling the Amsterdam criteria

PURPOSE: Germline mutations in mismatch repair genes predispose to hereditary nonpolyposis colorectal cancer (HNPCC). To address effective screening programs, the true incidence of the disease must be known. Previous clinical investigations reported estimates ranging between 0.5% and 13% of all the colorectal cancer (CRC) cases, whereas biomolecular studies in Finland found an incidence of 2% to 2.7% of mutation carriers for the disease. The aim of the present report is to establish the frequency of the disease in a high-incidence area for colon cancer. PATIENTS AND METHODS: Through the data of the local CRC registry, we prospectively collected all cases of CRC from January 1, 1996, through December 31, 1997 (N = 391). Three hundred thirty-six CRC cases (85.9% of the incident cases) were screened for microsatellite instability (MSI) with six to 12 mono- and dinucleotide markers. MSI cases were subjected to MSH2 and MLH1 germline mutation analysis and immunohistochemistry; the methylation of the promoter region was studied for MLH1. RESULTS: Twenty-eight cases (8.3% of the total) showed MSI. MSI cases differed significantly from microsatellite-stable (MSS) cases for their proximal location (P < .01), high mucinous component (P < .01), and poor differentiation (P = .002). Of MSI cases studied (n = 12), only one with a family history compatible with HNPCC had a germline mutation (in MSH2). Five other patients with a family history of HNPCC (two with MSI and three with MSS tumors) did not show germline mutations. CONCLUSION: We conclude that the incidence of molecularly confirmed HNPCC (one [0.3%] of 336) in a high-incidence area for CRC is lower than in previous biomolecular and clinical estimates.

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Immunohistochemistry Identifies Carriers of Mismatch Repair Gene Defects Causing Hereditary Nonpolyposis Colorectal Cancer

Journal of Clinical Oncology ◽

10.1200/jco.2005.05.180 ◽

2005 ◽

Vol 23 (21) ◽

pp. 4705-4712 ◽

Cited By ~ 24

Author(s):

Astrid T. Stormorken ◽

Inger Marie Bowitz-Lothe ◽

Tove Norèn ◽

Elin Kure ◽

Steinar Aase ◽

...

Keyword(s):

Colorectal Cancer ◽

Mismatch Repair ◽

Hereditary Nonpolyposis Colorectal Cancer ◽

Mismatch Repair Gene ◽

Repair Gene ◽

Predictive Values ◽

Blood Samples ◽

Bethesda Criteria ◽

Amsterdam Criteria ◽

Hereditary Nonpolyposis

Purpose Hereditary nonpolyposis colorectal cancer (HNPCC) may be caused by mutations in mismatch repair (MMR) genes. The aim of this study was to validate immunohistochemistry and family history as prescreening tools to predict germline mutations in MLH1, MSH2, and MSH6. Patients and Methods Pedigrees from 250 families were extended, cancer diagnoses were verified, and families were classified according to the Amsterdam and the Bethesda criteria. Tumor specimens were examined with immunohistochemistry for the presence of MLH1, MSH2, and MSH6 proteins. Mutation analyses were performed in blood samples from the same patients. Results Blood samples from affected index persons in 181 families and tumor specimens from 127 of the affected index persons were obtained. Thirty tumors lacked one or more gene products. Sensitivity of immunohistochemistry to detect mutation carriers was 100%, specificity was 82%, and positive predictive value was 85%. Sensitivities, specificities, and positive predictive values for the Amsterdam criteria were 82%, 8%, and 45%, respectively, and for the Bethesda criteria were 100%, 0%, and 48%, respectively. Distribution of mutations was MLH1 = 4, MSH2 = 11, and MSH6 = 4. Conclusion Wide clinical criteria to select HNPCC kindreds, followed by immunohistochemistry of tumor material from one affected person in each family, had high sensitivity and specificity to predict MMR mutations.

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