Target regions (includes 2 genes)
MLH1 (OMIM # 120436) - 3p22.2, MSH2 (OMIM # 609309) - 2p21
Lynch syndrome, also known as Hereditary Nonpolyposis Colorectal Cancer (HNPCC; OMIM #120435), is an inherited cancer syndrome, which results from germline mutations in the DNA mismatch repair (MMR) genes. They are responsible for the correction of small errors that occur in the DNA nucleotide sequence (mismatches) during DNA replication.
Mutations in MMR genes lead to genomic instability, characterized by a reduction or increase in the number of tandemly repeated sequences (microsatellites).
The microsatellite instability (MSI) leads to the occurrence of somatic mutations in oncogenes and/or in tumor-suppressor genes.
Lynch syndrome is characterized by an early onset and a very high risk of developing cancer, particularly in the right colon, but also in the endometrium, ovaries, stomach, bile ducts, kidneys, bladder, ureter, and brain.
Lynch syndrome is an autosomal dominant disorder with leading cause - a germline mutations in one of the four MMR genes: MLH1, MSH2, MSH6, and PMS2. Mutations in the MLH1 and MSH2 genes are in 80-90% of all patients with Lynch syndrome and are most often seen in families that strictly meet the Amsterdam II criteria. The rest of the patients have changes in the EPCAM, MSH6 and PMS2 genes.
In HNPCC patients, 10 to 27% of the pathogenic mutations in the MLH1 and MSH2 genes results from larger deletions and duplications which affect, for example, one or more exons that are not usually detectable by standard Sanger sequencing. Therefore the use of methods such as MLPA (Multiplex Ligation-Dependent Probe Amplification) is required.
Reason for Referral / Clinical Significance:
Candidates for this test are all patients who strictly meet the revised Bethesda criteria (persons with carcinoma from families fulfilling the Amsterdam criteria: colorectal or uterine tumor with early onset (before the age of 50); presence of synchronous, metachronous or other colorectal carcinoma, associated with HNPCC, regardless of the age of onset; CRC with a high degree of microsatellite instability (MSN) in patients under 60 years old; Persons with CRC in at least one first-generation relative of HNPCC-associated tumor, with tumor onset before the age of 50 years old. Persons with CRC in at least two first- or second-generation relatives with HNPCC – associated tumor, regardless of the age of onset).
Clinical characteristics of Lynch syndrome, defined by Amsterdam II criteria, include hereditary colorectal (Type I) or extracolonic (Type II) tumor in at least three relatives within at least two consecutive generations, with age of onset before 50 years old in at least one of the relatives, and excluding cases of familial adenomatous polyposis (FAP). The tumor must be histologically verified.
- Enables the identification of a hereditary genetic defect which affects the MMR genes in patients with colorectal cancer in whom the tumor has shown a positive IHH reaction and/or MCH;
- Allows confirmation of the diagnosis in the presence of a family history with early onset of colorectal cancer and a known deletion/duplication in the family;
- Allows the identification of a predisposition in an asymptomatic family member with a family history of colorectal carcinoma.
Interpretation of results:
The detection of deletions or duplications in the MLH1/MSH2 genes allows the diagnosis of Lynch syndrome.
The genetic counselor will interpret and answer all questions about your result.
Sensitivity of the method: 90%
Method: MLPA (Multiplex Ligation-Dependent Probe Amplification)
MLPA is a semi-quantitative method for determining copy number variations of DNA. The methodology is used to detect intragenic or whole-gene deletions or duplications. The analysis for searching for MLH1/MSH2 genes was performed using the kit SALSA MLPA P003 MLH1/MSH2 probemix, developed by MRC-Holland (Amsterdam, Holland).
What does the test involve?
· DNA isolation and sample storage.
· MLPA analysis to detect deletions/duplications in the MLH1, MSH2 and EPCAM genes.
· Forming a written result from the genetic test.
· Diagnostic interpretation of results and genetic counseling.
Sensitivity of the method: 90%
Biological material: Fresh or FFPE tumor tissue, or DNA isolated from Fresh or FFPE tumor tissue. For more information, please read the "Biological material requirements and shipping information" carefully.
