Methylation status of MLH1 gene (tumor tissue)
This test checks how methyl groups (chemical markers) are attached to the MLH1 gene in a tumor sample. MLH1 is involved in DNA repair and mutations or silencing can affect cancer progression.
["Assessing MLH1 methylation helps guide treatment decisions in certain cancers."]
Key facts at a glance
- LOINC
- 97760-3
- Short code
- MLH1 Methyl Anl Bld
- Synonyms
- MLH1 Methyl Anl Bld
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Ref low
- 1.5
- Ref high
- 9
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- molgen
- CPT
- 83002
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why This Test Matters for Cancer Care
MLH1 is part of a DNA repair system that protects cells from mutations. When this gene becomes silenced (often due to methylation), it may contribute to tumor growth. This test helps doctors determine if your cancer is likely to respond to specific treatments, such as those targeting microsatellite instability (MSI).
How the Test Works
A small sample of your tumor tissue is analyzed to detect chemical changes (methylation) on the MLH1 gene. Advanced lab techniques identify these markers, which may indicate how your cancer behaves and whether certain therapies could be more effective. This is typically done through specialized molecular testing methods, not blood or urine samples.
When This Test Is Ordered
Your doctor may recommend this test if you have certain types of cancers, such as colorectal, endometrial, or gastric cancers, and your tumor shows signs of microsatellite instability (MSI). It’s often part of a broader genetic evaluation to tailor treatment plans, especially for patients who may benefit from targeted therapies.
What to Expect Before the Test
No special preparation is needed unless instructed by your healthcare provider. You’ll likely have a small biopsy taken from your tumor during surgery or another procedure. The sample is then sent to a lab for detailed genetic analysis. Results are typically available within weeks.
Reference range
Follicular: 1.5-9.0 mIU/mLN/A
For females: inform if menstrual cycle status. For certain tests, timing within menstrual cycle may matter.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
MLH1 Methylation Test
Frequently asked questions
This test helps identify whether your cancer is associated with microsatellite instability (MSI-H), a genetic hallmark that may predict response to certain immunotherapies or targeted drugs. For example, cancers with MSI-H may benefit from treatments like pembrolizumab (Keytruda®).
Does this test require a specific type of cancer diagnosis?
How long does it take to get results from this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy