MLH1 and MSH2 mutation screening in HNPCC families of Hungary - Two new MMR gene mutations.

INTRODUCTION: Hereditary Non-Polyposis Colorectal Cancer is an inherited disease with deleterious germline mutations in the DNA mismatch repair genes causing the development of colon cancer and other malignancies. This is the first study in Hungary screening the population of our colorectal cancer patients in order to identify the prevalence of the disease. METHODS: In families who met the Modified Amsterdam and Bethesda Criteria the removed tumor tissue was first examined by immunohistochemistry and microsatellite instability analysis. Those cases which showed high microsatellite instability underwent DNA sequencing and multiple ligation dependent probe amplification. RESULTS: Of the 1576 patients with colorectal cancer underwent screening for the modified Amsterdam and Bethesda criteria, 69 (4.4%) and 166 (10.5%) fulfilled the criteria respectively. 15 patients (31%) of the Amsterdam positive group and 19 patients from the Bethesda positive (18.1%) were MSI-H. There were 8 pathogenic mutations identified in 9 families (60%) in the Amsterdam positive group. 5 mutations were found in 5 families (26%) in the Bethesda positive group. 12 pathogenic mutations were identified, two of these are newly identified, and being published first in this work. These two new mutations were located on MLH1 (g.31276_35231del) and MSH2 (c.969_970delTC) genes. CONCLUSION: The prevalence of the mutations in the MLH1 and MSH2 genes was almost equal in our Hungarian colorectal cancer patients. One mutation in the MLH1 gene (c.143A > C; p.Q48P) was identified in three different families. Whether this mutation is the most frequent in the Hungarian population is still unidentified and warrant further investigation.

A new mutation in Muir-Torre syndrome associated with familiar transmission of different gastrointestinal adenocarcinomas.

Hereditary Nonpolyposis Colorectal Carcinoma (HNPCC) is the most frequent inherited disease which can lead to the development of tumors in the colon and other locations. Its genetic basis is related to the germline mutation of the Mismatch Repair (MMR) genes. Muir-Torre syndrome is considered one of the subtypes of this disease, in which the HNPCC tumor spectrum is frequently associated with sebaceous carcinoma of the skin or keratoacanthoma. A 57 years old male patient is presented with a mucinous carcinoma of the caecum and an adenocarcinoma of the pancreas head. A malignant sebaceous carcinoma was removed from his left neck area. His family history was significant for two cases of colon carcinoma, two cases of stomach cancer and a case of metacron endometrial and skin tumor as well. Both the colon carcinoma and the skin tumor proved to be microsatellite unstable. An Arg>Pro switch missense mutation was found in codon 265 of the hMLH1 gene. This error was found in 4 other members of his family. The detected genetic alteration was considered pathogenic and was not published yet in English literature. The significance of this particular case is the rare tumor association in a patient with Muir-Torre syndrome (MTS). In cases of sebaceous skin lesions, evaluation of family history is of utmost importance in the early detection of HNPCC and in the follow up care of family members with the particular mutation.

Difficulties in recognizing families with Hereditary Non-polyposis Colorectal Carcinoma. Presentation of 4 families with proven mutation.

INTRODUCTION: Hereditary Non-polyposis Colorectal Carcinoma is the most frequent genetic disease leading to colon and other malignancies. Recognizing the condition requires extensive family history going back several generations focusing particularly on the types of tumors occurring in the family at different age groups. METHODS: In families who met the Amsterdam and Bethesda Criteria, the removed tumor tissue was first examined by immunohistochemistry and microsatellite instability analysis. Subsequently DNA sequencing was performed to detect an underlying Mismatch Repair Gene mutation and multiple ligation dependent probe amplification was applied for recognizing large deletions in Mismatch Repair Genes. RESULTS: In the investigated families 3 pathogen mutations, 1 large deletion and 2 cases of polymorphism were found. There is considerable difference between the families in terms of the types of malignancies and the age in which those appeared. CONCLUSION: Recognizing families with Hereditary Non-polyposis Colorectal Carcinoma presents great difficulties because of the variety of phenotypes in presentation. Special attention should be paid to small families and those who present with cancer of other than colon origin. Practicing physicians should be made aware of the fact that this disease may have atypical presentations. Follow up of families who have already been screened may be difficult for social, economical or religious reasons.