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26351 MLH1 Hypermethylation Analysis, Tumor (ML1HM)

MLH1 Hypermethylation Analysis, Tumor (ML1HM)
Test Code: ML1HMSO
Synonyms/Keywords

​​Hypermethylation

MLH1 Hypermethylation

Promoter Hypermethylation

MLH1HM​

Test Components

​Slide review; MLH1 Hypermethylation Analysis

Useful For

​An adjunct to MSI / Microsatellite Instability (MSI), Tumor and Mismatch Repair (MMR) Protein Immunohistochemistry Only, Tumor when colon or endometrial tumor demonstrates microsatellite instability (MSI-H) and loss of MLH1 protein expression, to help distinguish a somatic versus germline event prior to performing expensive germline testing.

An adjunct to negative MLH1 germline testing in cases where colon or endometrial tumor demonstrates MSI-H and loss of MLH1 protein expression.

Ordering Guidance:

This test is not recommended as a first-tier screening measure for hereditary nonpolyposis colon cancer. For more information see TMSI / Microsatellite Instability, Tumor and IHC / Mismatch Repair (MMR) Protein Immunohistochemistry Only, Tumor.

Testing will only be performed on colon or endometrial tumors demonstrating loss of MLH1 protein expression by immunohistochemistry.

Mayo Clinic's preferred screening test includes both MLH1 promoter hypermethylation and BRAF V600E testing. Order BRMLH / MLH1 Hypermethylation and BRAF Mutation Analysis, Tumor.

Extracted DNA from tissues is not an acceptable specimen type.

If the MMR immunohistochemistry (IHC) results for MLH1 and/or PMS2 suggest possible tumor heterogeneity, are ambiguous, or unusual, the physical IHC stains will be required to optimize the area of tissue selected for testing and for interpretation of the results. If IHC stains are required and not sent with the specimen, a request will be submitted to provide the IHC stains which will result in a slight delay.

Specimen Requirements
Specimen TypePreferred Container/TubeAcceptable Container/TubeSpecimen VolumeSpecimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
​Tissue​Tissue Block​Slides (refer to Collection Processing Instructions)
Collection Processing Instructions

Submit formalin-fixed, paraffin-embedded tissue block (preferred) or 1 slide stained with hematoxylin and eosin and 10 unstained, nonbaked slides (5-micron thick sections) of the tumor tissue.

Sections should contain tumor tissue.

Pathology report and MMR IHC results must accompany specimen in order for testing to be performed. At minimum, it should contain the following information:

1. Patient name

2. Block number-must be on all blocks, slides and paperwork (can be handwritten on the paperwork)

3. Tissue collection date

4. Source of the tissue

Acceptable Specimen Types

​Tissue block; or 1 slide stained with hematoxylin and eosin and 10 unstained, nonbaked slides (5-micron thick sections) of the tumor tissue.

Specimen Stability Information
Specimen Type ​Temperature
Varies​ ​ ​​Ambient (preferred)
​Frozen
​Refrigerated
Rejection Criteria
Specimens that have been decalcified (all methods). 
Specimens that have not been formalin-fixed, paraffin-embedded.
Bone marrow in EDTA.
Extracted DNA.
Interference

​Testing tumors other than colon or endometrial for MLH1 hypermethylation has not been fully evaluated, and these specimens are not accepted for testing.

Colon cancer is relatively common and it is possible for a sporadic colon cancer to occur in an HNPCC family. Therefore, evaluation of other family members should still be considered in cases with MLH1 promoter hypermethylation if there is high clinical suspicion of HNPCC.

Performing Laboratory Information
Performing LocationDay(s) Test Performed
Report Available
Methodology/Instrumentation
Mayo Clinic Laboratories​​Varies​7 to 14 days​Polymerase Chain Reaction (PCR) Analysis
Reference Lab
Test Information

​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 an abnormality in MLH1, and the most common cause of gene inactivation is promoter hypermethylation (epigenetic silencing). A specific mutation in the BRAF gene (V600E) has been shown to be present in approximately 70% of tumors with hypermethylation of the MLH1 promoter. Importantly, the V600E mutation is rarely identified in cases with germline MLH1 mutations. Thus, direct assessment of MLH1 promoter methylation status and testing for the BRAF V600E mutation can be used to help distinguish between a germline mutation and epigenetic/somatic inactivation of MLH1. Tumors that have the BRAF V600E mutation and demonstrate MLH1 promoter hypermethylation are almost certainly sporadic, whereas tumors that show neither are most often caused by an inherited mutation.

Although testing for the BRAF V600E mutation and MLH1 promoter hypermethylation are best interpreted together, they are also available separately to accommodate various clinical situations and tumor types. These tests can provide helpful diagnostic information when evaluating an individual suspected of having HNPCC/Lynch syndrome, especially when testing is performed in conjunction with MSI / Microsatellite Instability (MSI), Tumor and Mismatch Repair (MMR) Protein Immunohistochemistry Only, Tumor studies. It should be noted that these tests are not genetic tests, but rather stratify the risk of having an inherited cancer predisposition and identify patients who might benefit from subsequent genetic testing.

Reference Range Information

​An interpretative report will be provided.

Interpretation

​An interpretive report will be provided. The likelihood of a germline (inherited) mutation is very low in those cases where the tumor demonstrates MLH1 promoter hypermethylation and the normal tissue is unmethylated. The likelihood of a germline mutation is high in those cases where the tumor and normal tissue lack MLH1 promoter hypermethylation. In cases where the tumor and normal tissue demonstrate MLH1 promoter hypermethylation, this result will be interpreted as equivocal and a blood sample will be requested to confirm potential germline hypermethylation.

Outreach CPTs
CPTModifier
(if needed)
QuantityDescriptionComments
​81288​1
​88381​1​Slide Review
Synonyms/Keywords

​​Hypermethylation

MLH1 Hypermethylation

Promoter Hypermethylation

MLH1HM​

Test Components

​Slide review; MLH1 Hypermethylation Analysis

Ordering Applications
Ordering ApplicationDescription
​Cerner​MLH1 Hypermethylation Analysis, Tumor (ML1HM)
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Specimen TypePreferred Container/TubeAcceptable Container/TubeSpecimen VolumeSpecimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
​Tissue​Tissue Block​Slides (refer to Collection Processing Instructions)
Collection Processing

Submit formalin-fixed, paraffin-embedded tissue block (preferred) or 1 slide stained with hematoxylin and eosin and 10 unstained, nonbaked slides (5-micron thick sections) of the tumor tissue.

Sections should contain tumor tissue.

Pathology report and MMR IHC results must accompany specimen in order for testing to be performed. At minimum, it should contain the following information:

1. Patient name

2. Block number-must be on all blocks, slides and paperwork (can be handwritten on the paperwork)

3. Tissue collection date

4. Source of the tissue

Acceptable Specimen Types

​Tissue block; or 1 slide stained with hematoxylin and eosin and 10 unstained, nonbaked slides (5-micron thick sections) of the tumor tissue.

Specimen Stability Information
Specimen Type ​Temperature
Varies​ ​ ​​Ambient (preferred)
​Frozen
​Refrigerated
Rejection Criteria
Specimens that have been decalcified (all methods). 
Specimens that have not been formalin-fixed, paraffin-embedded.
Bone marrow in EDTA.
Extracted DNA.
Interference

​Testing tumors other than colon or endometrial for MLH1 hypermethylation has not been fully evaluated, and these specimens are not accepted for testing.

Colon cancer is relatively common and it is possible for a sporadic colon cancer to occur in an HNPCC family. Therefore, evaluation of other family members should still be considered in cases with MLH1 promoter hypermethylation if there is high clinical suspicion of HNPCC.

Useful For

​An adjunct to MSI / Microsatellite Instability (MSI), Tumor and Mismatch Repair (MMR) Protein Immunohistochemistry Only, Tumor when colon or endometrial tumor demonstrates microsatellite instability (MSI-H) and loss of MLH1 protein expression, to help distinguish a somatic versus germline event prior to performing expensive germline testing.

An adjunct to negative MLH1 germline testing in cases where colon or endometrial tumor demonstrates MSI-H and loss of MLH1 protein expression.

Ordering Guidance:

This test is not recommended as a first-tier screening measure for hereditary nonpolyposis colon cancer. For more information see TMSI / Microsatellite Instability, Tumor and IHC / Mismatch Repair (MMR) Protein Immunohistochemistry Only, Tumor.

Testing will only be performed on colon or endometrial tumors demonstrating loss of MLH1 protein expression by immunohistochemistry.

Mayo Clinic's preferred screening test includes both MLH1 promoter hypermethylation and BRAF V600E testing. Order BRMLH / MLH1 Hypermethylation and BRAF Mutation Analysis, Tumor.

Extracted DNA from tissues is not an acceptable specimen type.

If the MMR immunohistochemistry (IHC) results for MLH1 and/or PMS2 suggest possible tumor heterogeneity, are ambiguous, or unusual, the physical IHC stains will be required to optimize the area of tissue selected for testing and for interpretation of the results. If IHC stains are required and not sent with the specimen, a request will be submitted to provide the IHC stains which will result in a slight delay.

Test Components

​Slide review; MLH1 Hypermethylation Analysis

Reference Range Information

​An interpretative report will be provided.

Interpretation

​An interpretive report will be provided. The likelihood of a germline (inherited) mutation is very low in those cases where the tumor demonstrates MLH1 promoter hypermethylation and the normal tissue is unmethylated. The likelihood of a germline mutation is high in those cases where the tumor and normal tissue lack MLH1 promoter hypermethylation. In cases where the tumor and normal tissue demonstrate MLH1 promoter hypermethylation, this result will be interpreted as equivocal and a blood sample will be requested to confirm potential germline hypermethylation.

For more information visit:
Performing Laboratory Information
Performing LocationDay(s) Test Performed
Report Available
Methodology/Instrumentation
Mayo Clinic Laboratories​​Varies​7 to 14 days​Polymerase Chain Reaction (PCR) Analysis
Reference Lab
For billing questions, see Contacts
Outreach CPTs
CPTModifier
(if needed)
QuantityDescriptionComments
​81288​1
​88381​1​Slide Review
For most current information refer to the Marshfield Laboratory online reference manual.