1800 202 8726
IHC markers explained

TTF-1 and Napsin A: — What Positive Means on Your Report

These two abbreviations appear on almost every lung cancer pathology report in India. They are not a diagnosis on their own — they tell the pathologist where the cancer most likely started.

Medically reviewed by Dr. T. Raghavender Reddy, Medical Oncologist, MBBS · DM (Medical Oncology) · MD (Radiation Oncology) · Last reviewed September 2026

  • Origin markers — TTF-1 and Napsin A show whether the cancer likely started in the lung.
  • Positive is not a severity score — A positive result narrows the diagnosis to an origin — it is not a measure of how serious the cancer is.
  • They work as a pair — Both markers are usually tested together because each adds certainty to the other.
  • Your oncologist interprets them — The result makes sense only alongside your scans, biopsy site, and clinical picture.
4.8 · 800+ Google reviews · 15,000+ patients treated
Limited Slots Today

Talk to a medical oncologist

₹950   Today: FREE  ·  Including free written second opinion

Reply within 2 working hours
Report reviewed by a senior oncologist
Confidential. No commitment to start treatment.
or
Call 1800 202 8726
17+
Cancer Specialists
on Panel
96.9%
Breast Cancer
Survival Rate*
15,000+
Patients
Treated
4.8★
Google Rating
(800+ reviews)

TTF-1 positive means the cancer cells still make a protein normally found in lung tissue, pointing to the lung as the likely origin. Napsin A is a second marker that confirms this. When both are positive, the result strongly suggests lung adenocarcinoma. Your oncologist interprets both results alongside your scans and biopsy findings.

What do TTF-1 and Napsin A actually measure?

TTF-1 stands for Thyroid Transcription Factor-1. It is a protein normally made by cells in the lung and thyroid. When a cancer cell still produces it, the pathologist takes this as evidence that the cancer originated from, or behaves like, lung or thyroid tissue.

Napsin A is an enzyme found mainly in the cells lining the lung's small air sacs. It is more specific to lung than TTF-1. When both are positive together, the combination points strongly to lung adenocarcinoma — the most common subtype in non-smokers and in women across India.

Neither marker is measured by blood test. Both are detected using immunohistochemistry on a thin slice of biopsy tissue — a stain is applied, and the result is reported as positive or negative.

What does each result combination on my report mean?

  • TTF-1 positive, Napsin A positiveStrongly suggests lung adenocarcinoma as the origin. Your oncologist will confirm with your full clinical findings.
  • TTF-1 positive, Napsin A negativeMay point to lung origin but also raises the possibility of thyroid cancer. Further markers and clinical information help decide.
  • TTF-1 negative, Napsin A positiveUncommon combination. Still suggests possible lung adenocarcinoma. Additional testing will usually follow.
  • Both negativeSuggests the cancer did not originate in the lung or thyroid. A different panel of markers will be tested to find the likely origin.

Not sure what this means for you?

Share your reports and a senior oncologist will explain your options in plain language — no obligation to start treatment.

Meet the Specialists

17+ senior cancer specialists. One panel for your case.

Trained at AIIMS, Tata Memorial, and leading international centres. Combined 150+ years of experience. Every complex case is reviewed by 3+ of them — together.

Dr. Naresh Gundu
Medical Oncologist

Dr. Naresh Gundu

MBBS, DNB (Internal Medicine), DM (Medical Oncology)

View Profile
Dr. C. Raghavendra Reddy
Medical Oncologist

Dr. C. Raghavendra Reddy

MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)

View Profile
Dr. Bharati Devi Gorantla
Medical Oncologist

Dr. Bharati Devi Gorantla

MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)

View Profile
Dr. Owais Mohammed
Medical Oncologist

Dr. Owais Mohammed

MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)

View Profile
Dr. T. Raghavender Reddy
Medical Oncologist

Dr. T. Raghavender Reddy

MBBS, DM (Medical Oncology), MD (Radiation Oncology)

View Profile
Dr. N. Kiranmayee
Medical Oncologist

Dr. N. Kiranmayee

MBBS, DM (Medical Oncology), MD (Internal Medicine)

View Profile
Dr. Muralidhar Muddusetty
Surgical Oncologist

Dr. Muralidhar Muddusetty

MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)

View Profile
Dr. Raghavendra Naik
Surgical Oncologist

Dr. Raghavendra Naik

MBBS, MS (General Surgery), M.Ch (Surgical Oncology)

View Profile
Dr. Mohammed  Imaduddin
Surgical Oncologist

Dr. Mohammed Imaduddin

M.B.B.S, MS (General Surgery), M.Ch (Surgical Oncology)

View Profile
Dr. Vinay Mamidala
Surgical Oncologist

Dr. Vinay Mamidala

MBBS, MS(General Surgery), M.Ch(Surgical Oncology), FMAS, FARIS(Ongoing)

View Profile
Dr. Paila Gowri Naidu
Surgical Oncologist

Dr. Paila Gowri Naidu

MBBS, MS (General Surgery), M.Ch (Surgical Oncology), FMAS

View Profile
Dr. Venkata Sushma P
Radiation Oncologist

Dr. Venkata Sushma P

MBBS, MD (Radiation Oncology)

View Profile
Dr. Kirti Ranjan Mohanty
Radiation Oncologist

Dr. Kirti Ranjan Mohanty

MBBS, MD (Radiation Oncology)

View Profile
Dr. Gangadhar Vajrala
Radiation Oncologist

Dr. Gangadhar Vajrala

MBBS, MD (Radiation Oncology), MPH

View Profile
Dr. Basudev Pokhrel
Hematologist

Dr. Basudev Pokhrel

MBBS, M.D (Immunohematology & Blood Transfusion)

View Profile
Dr. Mohammed Imran
Interventional Radiologist

Dr. Mohammed Imran

View Profile
Dr. Vajja Sandeep Kumar
Surgical Oncologist

Dr. Vajja Sandeep Kumar

MBBS, MS (General Surgery), DrNB (Surgical Oncology), FALS Oncology

View Profile
Dr. Sridhar Kamani
Surgical Oncologist

Dr. Sridhar Kamani

MBBS, MS (General Surgery), DrNB (Surgical Oncology)

View Profile

Want a specific doctor for your case? Mention them when booking.

Book Free Consultation

You do not have to work this out alone

A 45-minute consultation with a specialist who treats this every week.

Book Free Consultation Call 1800 202 8726

What do the terms on my pathology report mean?

TTF-1
Thyroid Transcription Factor-1. A protein present in normal lung and thyroid cells. A cancer that tests positive likely started in one of these two organs.
Napsin A
An enzyme found mainly in the lung's air sacs. More specific to lung than TTF-1, and rarely positive in thyroid cancer.
IHC (Immunohistochemistry)
The laboratory technique used to detect these proteins. A stain is applied to a thin slice of tumour tissue; the result is read as positive or negative.
Adenocarcinoma
The most common lung cancer subtype. It develops in the cells lining the small air sacs, and is the type TTF-1 and Napsin A most reliably identify.
Positive
The marker was found in the tumour cells. The cancer produces that protein, which points to its likely tissue of origin.
Negative
The marker was not found. This means the cancer likely did not originate from that tissue type — not that the result is bad news.
Primary vs. secondary
Primary means the cancer started in that organ. Secondary means it spread there from elsewhere. These markers help the pathologist tell the two apart.

Did you know?

Lung adenocarcinoma is the subtype rising fastest among non-smoking women in India. TTF-1 is particularly useful when cancer has spread to lymph nodes or distant organs before the lung primary is identified.

Correctly naming where a cancer started changes the entire treatment approach — which is why these two markers appear on virtually every lung biopsy report.

Source: ICMR National Cancer Registry Programme; ESMO Clinical Practice Guidelines on Lung Cancer

What else do I need to understand about these markers?

TTF-1 is positive on my report. Does that confirm it is lung cancer?

A positive TTF-1 is strong evidence of lung or thyroid origin, but it is not a final diagnosis on its own. Your oncologist combines this result with your scan findings, the biopsy site, your symptoms, and other markers before reaching a conclusion. One marker does not replace that full clinical picture.

Why are two markers tested rather than one?

No single marker is perfectly specific. TTF-1 appears in both lung and thyroid cancers and occasionally in other tumours. Napsin A is more specific to lung and rarely appears in thyroid cancer. Using both together increases diagnostic accuracy — when they agree, the pathologist has considerably greater confidence in the origin.

My report gives a score like TTF-1 3+ or says strong staining. What does that mean?

Some laboratories report staining intensity on a scale — 1+, 2+, 3+ — or as weak, moderate, or strong. A stronger score means a higher proportion of tumour cells carry the protein. Treatment decisions are not based on staining intensity alone; ask your oncologist what the score means for your specific case.

Can these markers tell whether the cancer will respond to treatment?

TTF-1 and Napsin A identify the cancer's origin only — they are not predictive markers. Separate markers such as EGFR, ALK, or PD-L1 address treatment options. If you are asking about targeted therapy or immunotherapy eligibility, ask your oncologist which predictive tests were performed on your sample.

Can a different laboratory give a second opinion on my slides?

Yes. Pathology slides and tissue blocks can be sent to any accredited laboratory for a second opinion. This is a common and reasonable step. Ask the original laboratory for your paraffin-embedded tissue block or spare slides, and ask your oncology team to guide you on how to arrange this.

Both markers are negative on my report. Does that mean the diagnosis is wrong?

No. A negative result on both means the cancer is unlikely to have started in the lung or thyroid. The pathologist will test a different marker panel suited to other origins. This is standard diagnostic practice — it narrows the search and does not indicate anything has gone wrong.

Explore 112 more Markers, Molecular Testing and Test Accuracy topics

HUB — How Accurate Is a Biopsy? Repeats, Errors and Second Opinions

HUB — IHC and Molecular Markers on a Biopsy

HUB — Labs, Slides and Second Opinions on a Biopsy

All Markers, Molecular Testing and Test Accuracy →

Next step

Still not sure what applies to you?

Send your reports across and a senior medical oncologist will go through what they mean, what is known, and what the options actually are.

Book Free Consultation Call 1800 202 8726
Common questions

Frequently asked questions

What does TTF-1 positive mean on a cancer report?

It means the cancer cells produce a protein normally found in lung and thyroid tissue, pointing toward one of those origins. It is one piece of evidence — your oncologist interprets it alongside your scans, biopsy site, and other markers before confirming a diagnosis.

Are TTF-1 and Napsin A the same test?

No. TTF-1 is a transcription factor found in lung and thyroid cells. Napsin A is an enzyme specific to the lung's air sacs and rarely appears in thyroid cancer. Testing both together gives the pathologist more certainty than either marker can provide on its own.

What cancer type is TTF-1 and Napsin A positive?

When both are positive, the result most strongly suggests lung adenocarcinoma — the most common lung cancer in India, and the subtype most often seen in non-smokers. TTF-1 alone can also appear in thyroid cancers. Your oncologist interprets the full panel in context.

Does a negative TTF-1 mean I do not have lung cancer?

Not necessarily. Some lung cancer subtypes — squamous cell and small cell — are often TTF-1 negative. A negative result means the pathologist will look at markers suited to those subtypes instead. It narrows the diagnostic search rather than ruling lung cancer out.

Why does my report have so many markers with plus and minus signs?

A diagnosis at this level of detail requires a panel of markers, not a single test. Each result — positive or negative — is one piece of evidence. The pathologist weighs them together to identify the most likely origin and subtype. No single result stands alone.

Can I ask for the pathology report to be explained to me?

Yes, and you should. You are entitled to a copy of your report. Your oncologist is the right person to explain each result in the context of your case. If the consultation feels rushed, ask for dedicated time to go through it, or seek a second opinion.

Full index

Browse all 701 biopsy topics

Every page in this section, grouped by the part of the journey it belongs to. Pick a group to see what is in it.

What Is a Biopsy?

What Is a Biopsy? Everything You Need to Know →

Types of Biopsy Compared

Which Biopsy Will You Have? Techniques Compared →

Preparing for a Biopsy

What to Expect on the Day of Your Biopsy →

Recovery and Aftercare

After a Biopsy: Recovery, Aftercare and Warning Signs →

Biopsy by Body Part

Biopsy by Body Part: What to Expect at Each Site →

Understanding Your Report

How to Read a Biopsy Report: Terms Explained →

IHC and Molecular Markers

IHC and Molecular Markers on a Biopsy: What They Mean →

Grading and Scoring Systems

Cytology & Prostate Scoring Systems Explained →

How Accurate Is a Biopsy?

How Accurate Is a Biopsy? Errors and Second Opinions →

If Your Result Is Benign

Your Biopsy Is Benign: What It Means and What Comes Next →

Call now Book free consultation