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HER2, BRAF and MSI in bile duct cancer: what a positive result means | CION Cancer Clinics
HER2, BRAF V600E and MSI-high are three uncommon changes that a molecular test can find in a bile duct cancer. Each one can open a medicine that targets that exact change, usually after first treatment. This page explains what each marker is, how the tumour is tested, who these medicines do not suit and what is realistically available in India. At CION Cancer Clinics in Hyderabad, our oncologists explain liver cancer in plain words and plan care around you and your family.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed October 2026, next review due October 2027
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On this page
- What do HER2, BRAF and MSI mean in bile duct cancer?
- What is each of the three markers?
- How do doctors test a bile duct cancer for these changes?
- What do the words on a molecular report mean?
- Who do these targeted treatments not suit?
- What this page cannot tell you
- Common questions about HER2, BRAF and MSI in bile duct cancer
The short answer
What do HER2, BRAF and MSI mean in bile duct cancer?
They are three uncommon changes that a molecular test can find inside a bile duct cancer. Each one can open a treatment that targets that exact change, usually after standard first treatment. Most bile duct cancers carry none of them, which is why the tumour has to be tested rather than guessed at.
Where they fit among the other markers
Intrahepatic cholangiocarcinoma is a cancer of the small bile ducts inside the liver. When the tumour DNA is tested, doctors look first for the better-known changes, FGFR2 fusions and IDH1 mutations. HER2, BRAF and MSI are found less often. They matter because each has a medicine already used for the same change in other cancers.
Why it is worth looking for something uncommon
A rare change is still a real option for the person who has it. Testing for all of them happens on the same tissue, at the same time, so looking adds little once the panel is ordered. Our page on why every biliary cancer should be molecularly tested explains the wider case.
A marker on a report is a possible option, not a promise. Your oncologist decides whether it applies to you.One at a time
What is each of the three markers?
They are different kinds of change, found by different parts of the test, and they lead to different families of medicine.
HER2
A protein on the surface of some cancer cells. When the cell makes far too much of it, the cancer is called HER2-positive. It is seen more often in gallbladder cancer and in cancers of the ducts outside the liver than in those inside it.
Medicines that target it
- Trastuzumab-based combinations
- Trastuzumab deruxtecan
- Newer HER2 antibodies, mostly abroad or in trials
BRAF V600E
A single spelling change in the BRAF gene that keeps a growth signal switched on. It is the same change seen in some melanomas and bowel cancers.
Medicines that target it
- Dabrafenib taken together with trametinib
MSI-high or dMMR
The cancer has lost its DNA spell-checker, so it collects many mistakes. Those mistakes make it easier for the immune system to spot, which is why immunotherapy can work unusually well here.
Medicines that use it
- Pembrolizumab and similar immunotherapy
MSI can also run in families
Sometimes MSI-high cancer comes from an inherited condition called Lynch syndrome. If so, relatives may be offered testing, with genetic counselling first.
Not sure whether this applies to you?
Ask an oncologistFrom biopsy to result
How do doctors test a bile duct cancer for these changes?
Enough tissue is taken
The biopsy that confirmed the cancer is usually the starting point. If the sample was very small, a fresh biopsy may be needed. CION arranges this through its diagnostic and pathology partners.
Staining for HER2 and MMR
A pathologist stains thin slices of the tumour. One stain shows how much HER2 protein is present. Others show whether the mismatch repair proteins are missing.
A gene panel reads the DNA
Next-generation sequencing reads many genes at once. It picks up BRAF, FGFR2, IDH1 and MSI status together, so one test answers most questions.
The tumour board reads the result
Your oncologist and the tumour board look at the report alongside your scans, liver function and fitness, and decide whether a match changes the plan now or later.
On your report
What do the words on a molecular report mean?
- HER2 IHC score
- A stain graded from zero up to three plus. The highest grade usually means HER2-positive. A middle grade may need a second test to settle it.
- Amplification
- Extra copies of a gene. HER2 amplification means the cell has too many copies of the HER2 gene, so it makes too much of the protein.
- BRAF V600E
- The exact BRAF change that current BRAF medicines are made for. Other BRAF changes exist, and they do not respond in the same way.
- MSI-high
- Microsatellite instability high. The DNA spell-checker is broken. MSS, or microsatellite stable, means it works normally.
- dMMR or pMMR
- Deficient or proficient mismatch repair. dMMR is the staining version of MSI-high, and the two usually agree.
- Variant of uncertain significance
- A change the laboratory cannot yet classify. It does not lead to a targeted medicine.
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Did you know
Some of these medicines are approved for any cancer that carries the change, wherever in the body it started. Doctors call this a tumour-agnostic approval. It is why a bile duct cancer with BRAF V600E or MSI-high may be treated with a medicine first known for another cancer.
Not for everyone
Who do these targeted treatments not suit?
They do not suit anyone whose tumour does not carry the change. A negative test means the medicine is not expected to help, and taking it anyway brings side effects without the benefit. Most people with bile duct cancer fall into this group, and their first treatment is usually chemotherapy with gemcitabine and cisplatin, often with immunotherapy added. See chemotherapy for gallbladder and bile duct cancer.
Other people for whom it may not be right
Someone who is very unwell, in bed most of the day, may gain more from comfort-focused care than from a new medicine. A liver that is struggling, with deep jaundice that has not been relieved by a stent, can make some medicines unsafe until the bile is draining again. A borderline HER2 result may not qualify at all.
Availability in India is uneven
Trastuzumab, dabrafenib, trametinib and pembrolizumab are available in India, but their approved uses here may not include bile duct cancer. Some newer HER2 medicines are not approved in India and are reached only by import or a trial. Your oncologist will tell you what is realistic, including cost.
Being straight with you
What this page cannot tell you
It cannot tell you whether your cancer carries any of these changes. Only a test on your tumour can answer that. It also cannot tell you whether a positive result should change your treatment now, later, or not at all. That depends on your stage, what you have already had, your liver function and how well you are.
The evidence is still young
Because these changes are uncommon, the studies behind these medicines in bile duct cancer were small. They show real responses in some people, but they cannot predict how you will do. Be wary of anyone who presents a marker as a sure answer.
Who to ask
Bring the full molecular report, not just the summary page, to your medical oncologist. If the report is unclear, ask for it to be reviewed by the tumour board. If a medicine is only open through a study, our guide to finding liver cancer trials in India explains how to look.
Not sure whether your tumour was ever tested? Call the helpline with your biopsy report and someone will check what was done.Questions we are asked
Common questions about HER2, BRAF and MSI in bile duct cancer
Is HER2 in bile duct cancer the same as in breast cancer?
It is the same protein and is tested in a similar way, but the scoring rules and the medicines that help are not identical. A result from a breast cancer guideline cannot simply be copied across. Your pathologist reports it using the method set for the type of cancer that was biopsied.
Can a blood test find these changes instead of a biopsy?
Sometimes. A liquid biopsy looks for tumour DNA in the blood and can pick up BRAF and some other changes. It can miss them when little tumour DNA reaches the blood, and it is weaker for HER2. Tissue remains the first choice when there is enough of it.
If my cancer is MSI-high, should my family be tested?
Possibly. MSI-high cancer is sometimes linked to Lynch syndrome, an inherited condition. A further test on your blood can show whether you were born with the change. If you were, a genetic counsellor can guide which relatives to test. Nobody is at fault for an inherited change.
Will a targeted medicine replace chemotherapy?
Usually not at first. In most plans, standard chemotherapy with or without immunotherapy comes first, and a targeted medicine is used when the cancer grows again. MSI-high can be an exception, where immunotherapy may move earlier. Your oncologist explains the order for you.
Does having one of these changes make the cancer worse?
Not in a simple way. The change describes how the cancer grows, not how far it has spread. The stage, the liver and your general health matter far more to how things go. What the marker adds is a possible extra line of treatment.
My report shows a BRAF change but not V600E. Does it count?
Usually not for the current BRAF tablets, which were studied in V600E. Other BRAF changes behave differently and may not respond. Some are of interest in trials. Ask your oncologist to explain what your exact change means before you read anything online.
How long does molecular testing take?
Staining results come back sooner than a full gene panel, which takes longer because the DNA is sequenced. Ask the laboratory for a likely date when the sample is sent. Treatment does not always need to wait, since first-line chemotherapy can often start meanwhile.
Can CION arrange the testing and the treatment?
CION arranges molecular testing through diagnostic and pathology partners, and the tumour board reviews the result. Targeted therapy, immunotherapy and chemotherapy are given at CION centres. Call the helpline with your reports and someone will explain the next step.
Your Specialists
Meet CION's liver cancer specialists. Bring your scan reports and liver blood tests.
Our medical and surgical oncologists plan liver cancer care together, weighing the tumour and how well your liver works before choosing surgery, a liver-directed procedure or medicines.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
Surgical Oncologist
Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
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Sources
- American Cancer Society — Bile Duct Cancer Targeted Therapy
- American Cancer Society — Bile Duct Cancer Immunotherapy
- National Cancer Institute — Bile Duct Cancer Treatment
- National Cancer Institute — Targeted Therapy for Cancer
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Why every biliary cancer should be molecularly testedThe case for testing, before you read about any one markerFGFR2 fusions in bile duct cancerThe most common targetable change in cancers inside the liverIDH1 mutations in bile duct cancerThe other marker every report should mentionImmunotherapy for pancreatic and biliary cancerHow immunotherapy is used, including for MSI-high cancer
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Send us your biopsy and molecular reports and we will tell you what was tested and what may still be worth checking. One helpline serves every CION centre.