Methylation-specific real-time PCR
Hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch Syndrome, is an autosomal dominant condition associated with increased risk of multiple cancers particularly colorectal and endometrial. This syndrome most commonly results from mutations of genes encoding DNA mismatch repair proteins including MLH1, MSH2, MSH6 and PMS2. These mutations lead to tumors with microsatellite instability (MSI) – a change in length of a microsatellite allele due to either insertion or deletion of repeating units. MSI can also occur in sporadic colorectal, endometrial and other cancers in patients without HNPCC. In sporadic cancers, MSI is typically associated with silenced MLH1 protein expression resulting from somatic hypermethylation of the MLH1 promoter. However, constitutional epimutations that result in germline MLH1 promoter hypermethylation also exist. Germline MLH1 promoter hypermethylation may confer an HNPCC (Lynch) syndrome phenotype even in the absence of primary sequence alternations in the MLH1 gene. Germline MLH1 promoter methylation can be documented by detecting methylation in non-neoplastic tissue (peripheral blood). Genetic counseling may be indicated based on the clinical and laboratory findings
Please note this “Germline MLH1 Promoter Methylation” test is a distinct orderable and has a different indication than the standard “MLH1 Promoter Methylation” test. The Germline MLH1 Promoter Methylation test is used to evaluate for constitutional MLH1 promoter methylation in peripheral blood specimens. The standard MLH1 Promoter Methylation test is used to evaluate for MLH1 promoter methylation in tumor specimens from formalin-fixed paraffin-embedded tissue blocks.
Interpretive report provided.
Specimens submitted for Molecular Diagnostics testing may contain substances that can inhibit PCR gene amplification. If an inhibitor is known to be present, attempts will be made to clear the specimen of inhibitor prior to amplification. Known inhibitors include heparin, medications and some levels of hemoglobin or IgG. The major inhibitor we see in our laboratory is heparin; avoid drawing blood in a heparin tube or through a heparinized port. For molecular diagnostics testing, a lavender top (EDTA) tube is preferred. If specimens containing heparin must be submitted, note "heparin" on the requisition to alert the lab to 'clean' the specimen before analysis thus reducing turnaround time, improving retention of DNA in the specimen and increasing our ability to return a conclusive result.
3 - 10 days
- Hereditary Nonpolyposis Colorectal Cancer (HNPCC)
- Lynch Syndrome
Collect blood in a lavender top tube. Refrigerate and send intact blood or bone marrow specimen within 24 hours of collection.
By ordering this test the clinician acknowledges that informed consent has been obtained from the patient as required by applicable state or federal laws and the ordering clinician has authorization from the patient permitting MLabs to report the test results to the ordering clinician. Test includes pathologist interpretation of results billed as a separate additional charge. This test is not available without interpretation.