MLH1 Promoter Hypermethylation by PCR

Formalin-fixed, paraffin-embedded tissue blocks; fixed in 10% neutral-buffered formalin for at least 6 hours, and not more than 48 hours. Tissue should be prepared in sections between 4 and 6 microns thick. Cell blocks and cytospins made from FNA (fine needle aspirates). Cytopathology ThinPrep slides with morphologic correlation. EDTA decal specimens are accepted.

This test is used to help rule out Lynch Syndrome. This assay should only be used in support of diagnosis. Positive and negative results should be interpreted in the context of all clinical information and other laboratory test results.

Hereditary nonpolyposis colon cancer (HNPCC), also known as Lynch syndrome, is an inherited cancer syndrome caused by a germline mutation in one of several genes involved in DNA mismatch repair (MMR), including MLH1, MSH2, MSH6, and PMS2. There are several laboratory-based strategies that help establish the diagnosis of HNPCC/Lynch syndrome, including testing tumor tissue for the presence of microsatellite instability (MSI-H) and loss of protein expression for any one of the MMR proteins by immunohistochemistry (IHC). It is important to note, however, that the MSI-H tumor phenotype is not restricted to inherited cancer cases; approximately 20% of sporadic colon cancers are MSI-H. Thus, MSI-H does not distinguish between a somatic (sporadic) and a germline (inherited) mutation, nor does it identify which gene is involved. Although IHC analysis is helpful in identifying the responsible gene, it also does not distinguish between somatic and germline defects. Defective MMR in sporadic colon cancer is most often due to MLH1, most often promoter hypermethylation (epigenetic silencing). Thus, direct assessment of MLH1 promoter methylation status can be used to help distinguish between a germline mutation and epigenetic/somatic inactivation of MLH1. Tumors that demonstrate MLH1 promoter hypermethylation are almost certainly sporadic, whereas tumors that show no hypermethylation are most often caused by an inherited mutation.

Copy of the referring client's requisition form and pathology report to accompany specimen.

Room temperature or refrigerated. Ship in cooled container during summer months.

Tissue not verified for the presence of tumor and specimens fixed in fixatives other than formalin are not acceptable. Samples <5-10% tumor burden will not be tested, as false negative results cannot be ruled out. Surgical pathology report not included. Only specimens decalcified in EDTA will be accepted for molecular testing. Testing may be cancelled if a sufficient amount of DNA cannot be extracted.

2 years: raw data and DNA, 10 years: FFPE

Only tissue that is clearly invasive carcinoma (established by histopathologic criteria) should be tested. Selection of tissue for the PCR assay should be performed by a pathologist.

This test was developed and its performance characteristics determined by CellNetix Labs LLC. The U.S. Food and Drug Administration (FDA) has not approved or cleared this test. However, FDA approval or clearance is currently not required for clinical use of this test. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions. CellNetix is authorized under Clinical Laboratory Improvement Amendments (CLIA) to perform high-complexity testing.

This is a reflex test based on the results of MMR IHC or MSI PCR testing.