MLH1 Methylation : 39782

MLH1Q or 39782

MLH1 Promoter Methylation

Formalin fixed paraffin embedded tissue or whole blood.

Preferred Specimens: 5 mL whole blood collected in an EDTA (lavender-top) tube or ACD (yellow-top) tube or Formalin fixed paraffin embedded tissue block or 1 H&E slide and 5 (2) unstained, non-baked slides with 5-10 um thick tumor sections

Alternative Specimen: Whole blood collected in sodium heparin (green-top) tube (not recommended)

Minimum volume:  whole blood 3 mL

Room temperature.

Whole blood: Room temperature: 8 days; Refrigerated: 8 days; Frozen: Unacceptable
FFPE: Room temperature: 5 years; Refrigerated: 5 years; Frozen: Unacceptable
Slides Room temperature: 5 years; Refrigerated: Unacceptable; Frozen: Unacceptable

Baked slide

Wednesday

7 days (From receipt at performing laboratory)

Not detected

The MLH1 methylation assay is designed to target methylated CpG residues in the “C region of the MLH1 promoter. The target patients are the people with colorectal cancer who have positive MLH1 IHC or MSI high results. Promoter methylation of MLH1 can help to rule out Lynch syndrome in colorectal cancer patients, as well as women with endometrial cancer. Lynch syndrome is most frequently caused by inherited germline mutation of one or more of the DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6, PMS2). The current NCCN guideline recommended testing for loss of protein expression of these MMR genes using immunohistochemistry (IHC) or microsatellite instability by PCR. MLH1 is the protein most often found to be downregulated or completely absent, often in combination with PMS2. This loss of expression of MLH1 can either be the result of a germline mutation(s) in the MLH1 gene (indicating Lynch syndrome), or due to promoter methylation (indicating a sporadic CRC). Few cases exist MLH1 germline methylation in Lynch syndrome. Usually there is 27.7-77.2% of concordance between BRAF mutation and MLH1 methylation confirming sporadic CRC.