IHC Marker - MSI (Microsatellite Instability) Test
About IHC Marker - MSI (Microsatellite Instability) Test
| Field | Value |
|---|---|
| Also Known As | MSI by IHC, MMR IHC, MMR Panel by IHC, Mismatch Repair Protein Immunohistochemistry, dMMR Testing |
| Sample Type | Formalin-fixed, paraffin-embedded (FFPE) tumour tissue block |
| Fasting Required | No fasting required |
| Report Time | 7 days |
| Recommended For | All genders and ages; typically ordered for patients diagnosed with colorectal, endometrial, or other solid tumours |
| Price | Starting at ₹6,720 |
What is an IHC Marker - MSI (Microsatellite Instability) Test?
The IHC Marker - MSI (Microsatellite Instability) test is a specialised laboratory test performed on tumour tissue. It checks whether four key DNA repair proteins are present or absent in cancer cells. Doctors order this test to understand how a tumour behaves and to guide treatment decisions. It is also known as the MMR IHC test, MSI by IHC, or Mismatch Repair Protein Immunohistochemistry.
What Does an IHC Marker - MSI (Microsatellite Instability) Test Measure?
The IHC Marker - MSI test examines four mismatch repair (MMR) proteins. These proteins work in pairs to fix errors that occur when DNA copies itself. When one or more of these proteins is missing from tumour cells, it signals a defect in the DNA repair process.
The four proteins assessed are listed below.
| Protein | Role |
|---|---|
| MLH1 (MutL Homolog 1) | Corrects DNA copying mistakes; its loss may point to Lynch syndrome or tumour-specific changes |
| PMS2 (PostMeiotic Segregation Increased 2) | Works as a partner to MLH1; typically absent when MLH1 is lost |
| MSH2 (MutS Homolog 2) | Recognises DNA mismatches; its absence suggests inherited or acquired repair defects |
| MSH6 (MutS Homolog 6) | Works as a partner to MSH2; typically absent when MSH2 is lost |
When all four proteins are present, the tumour is classified as MMR-proficient (pMMR) or Microsatellite Stable (MSS). When one or more proteins are absent, the tumour is classified as MMR-deficient (dMMR) or MSI-High (MSI-H).
Why is an IHC Marker - MSI (Microsatellite Instability) Test Done?
Doctors order the IHC MSI test for several reasons, from confirming a suspected hereditary cancer condition to assessing whether a patient may respond to certain cancer treatments.
Common Symptoms That May Require This Test
The following symptoms may prompt a doctor to order this test, particularly in patients already diagnosed with or suspected of having cancer.
- Unexplained or rapid weight loss
- Persistent change in bowel habits
- Rectal bleeding without a clear cause
- Ongoing abdominal pain
- Family history of colorectal or endometrial cancer
- Cancer diagnosed before the age of 50
Conditions This Test Can Help Detect
The MSI by IHC test helps identify a range of cancer-related conditions. These include the following.
- Lynch syndrome (hereditary nonpolyposis colorectal cancer), which is linked to inherited mutations in MLH1, MSH2, MSH6, or PMS2
- Sporadic colorectal cancer with MSI-High status, found in roughly 15% to 20% of non-hereditary cases
- Endometrial cancer with mismatch repair deficiency
- MSI-High solid tumours, including gastric, ovarian, biliary tract, pancreatic, breast, and prostate cancers
- Eligibility for immune checkpoint inhibitor therapy, such as pembrolizumab
How to Prepare and What to Expect
Because the IHC Marker - MSI (Microsatellite Instability) test is performed on tumour tissue rather than a blood or urine sample, preparation is different from a routine test.
Do You Need to Fast?
No fasting is required. This test uses a tissue sample that has already been collected during a surgical procedure or biopsy.
Practical Tips Before Your Test
Keep the following points in mind before submitting your sample.
- Bring a detailed clinical history, including your symptoms, previous test results, and family history, as this is required for the test.
- Tissue blocks are preferred over slides for the best results.
- Ensure the pathology report from the original tissue collection accompanies your sample.
- Confirm with your treating doctor that the tissue was collected from a surgical excision rather than a small biopsy, as adequate tumour content is needed.
- The tissue block should contain at least 20% tumour nuclei for colorectal specimens and at least 40% for endometrial specimens.
Step-by-Step Procedure
The following steps describe how the test is typically carried out.
- The formalin-fixed, paraffin-embedded (FFPE) tumour tissue block collected during your surgery is submitted to the laboratory along with your clinical history and pathology report.
- Laboratory technologists cut thin sections from the tissue block and place them on glass slides.
- The slides are treated with specific antibodies that attach to each of the four MMR proteins, making them visible under a microscope.
- A pathologist examines the stained slides and compares the protein staining in tumour cells with the staining in adjacent healthy tissue, which acts as an internal reference.
- Based on whether each protein shows intact or absent staining, the pathologist classifies the tumour as pMMR/MSS or dMMR/MSI-H.
- A detailed report is prepared and delivered within the stipulated turnaround time.
Factors That Can Affect Accuracy
Several factors can influence the reliability of the test result.
- Poor fixation of the original tissue sample
- Insufficient tumour cell content in the tissue block
- Tumour cell percentage below 20%, which may cause MSI to go undetected
- Damage to tissue from prior chemotherapy or radiation
- Absence of adequate internal control tissue on the slide
Understanding Your IHC Marker - MSI (Microsatellite Instability) Test Results
The MMR Panel by IHC report classifies tumour tissue based on protein expression patterns. Your treating oncologist or pathologist will explain what the findings mean for your specific situation.
| Classification | Meaning |
|---|---|
| MMR-Proficient (pMMR) / Microsatellite Stable (MSS) | All four MMR proteins show intact nuclear staining; DNA repair function is normal |
| MMR-Deficient (dMMR) / MSI-High (MSI-H) | Complete loss of one or more MMR proteins; DNA repair is defective |
| MSI-Low (MSI-L) | One marker shows instability; some laboratories classify this as MSS for clinical purposes |
These ranges are general guidelines. Your doctor will interpret your results based on your age, health history, and other factors. Always consult a qualified healthcare professional for personalised medical advice.
Results During Special Conditions
Certain situations can affect how results should be read.
Poor tissue fixation or rare protein variants where the antibody binding site is altered can cause a false loss of MMR protein staining, potentially suggesting dMMR when the DNA repair system is actually intact. Prior chemotherapy or radiation treatment may also alter tissue quality and protein expression, which the reporting pathologist will take into account.
How to Maintain Healthy Levels
If your result indicates dMMR or MSI-High status, the following general steps are worth discussing with your healthcare team.
- If Lynch syndrome is confirmed, follow the recommended surveillance schedule for early detection of associated cancers.
- First-degree relatives of Lynch syndrome patients should consider genetic counselling and testing.
- A balanced diet, regular physical activity, and avoidance of smoking support overall health and may help reduce broader cancer risk.
Lupin Diagnostics IHC Marker - MSI (Microsatellite Instability) Test Price
The IHC Marker - MSI (Microsatellite Instability) test is available at Lupin Diagnostics starting at ₹6,720. This test requires a visit to a Lupin Diagnostics centre; home collection is not available as the test is performed on tumour tissue submitted from a surgical or pathology procedure.
| City | Approximate Price (₹) |
|---|---|
| BHOPAL | 6720 |
| CHENNAI | 6720 |
| HYDERABAD | 6720 |
| KOLKATA | 6720 |
| NAVI MUMBAI | 6720 |
| PUNE | 6720 |
Prices are indicative and may vary by location. Please confirm the current price at the time of booking.
How to Book
- Select the IHC MSI test on the Lupin Diagnostics website.
- Choose your city and preferred centre location.
- Visit the centre at your scheduled time to submit your FFPE tissue block along with the required clinical history and pathology report.
- Receive your report via email or WhatsApp within the stipulated turnaround time.
Frequently Asked Questions
Microsatellite instability refers to changes in the length of short, repetitive DNA sequences found throughout the genome. These changes occur when DNA repair proteins fail to correct errors during cell division. The IHC Marker - MSI test detects this indirectly by checking whether the repair proteins are present in tumour cells.
The MSI by IHC result helps doctors decide on the most appropriate treatment. Patients with MSI-High or dMMR tumours may be eligible for immune checkpoint inhibitor therapy, which works differently from standard chemotherapy. The result also helps identify whether a hereditary cancer syndrome, such as Lynch syndrome, may be involved.
Not necessarily. MSI-High status can arise spontaneously in a tumour without any inherited mutation, particularly through epigenetic silencing of the MLH1 gene. Further testing, such as MLH1 methylation analysis or germline genetic testing, is needed to confirm or rule out Lynch syndrome.
No. The IHC Marker - MSI (Microsatellite Instability) test cannot be done at home because it requires a tumour tissue block, which is obtained during a surgical or biopsy procedure at a hospital. The block is then submitted directly to the laboratory.
At Lupin Diagnostics, the report for the IHC MSI test is typically available within 7 days of the tissue block being received at the laboratory.
Bring the FFPE tumour tissue block along with a detailed clinical history that includes your symptoms, previous test results, relevant imaging reports, and family history of cancer. The original pathology report from tissue collection should also accompany the sample, as this information is required to process and interpret the test accurately.
Your treating oncologist will review the result alongside your overall diagnosis and other test findings. Depending on the outcome, they may recommend additional molecular tests, refer you to a genetic counsellor, or discuss treatment options including immunotherapy. This test result is one part of a wider clinical assessment.
IHC Marker - MSI (Microsatellite Instability) Test
