Biopsies Don't Spread Cancer: Oncologist Busts Popular Cancer Myth

When a doctor recommends a biopsy, many patients immediately become anxious—not because of the procedure itself, but because of a long-standing belief that disturbing a tumour can cause cancer to spread.

This misconception has been passed down through families, neighbours and communities for decades. Even today, it continues to discourage people from getting tested, particularly in parts of India where misinformation often spreads faster than medical facts.

According to Dr Mandeep Singh Malhotra, Surgical and Molecular Oncologist, Founder and Chief Mentor of Art of Healing Cancer, Gurugram, this is one of the most common fears he hears from patients.

"Almost every week, someone tells me, 'Doctor, if you cut it, it will spread.' Families repeat it, neighbours reinforce it, and patients postpone the test."

Doctors say this delay, not the biopsy itself, is what can allow cancer to grow, spread and become harder to treat.

What Exactly Is A Biopsy?

A biopsy is a medical procedure in which doctors remove a small sample of tissue or cells from a suspicious lump or abnormal area. The sample is then examined under a microscope by a pathologist to determine whether cancer is present.

Depending on where the abnormal tissue is located, doctors may perform different types of biopsies. A fine needle aspiration (FNAC) uses a thin needle to collect cells, while a core needle biopsy removes a slightly larger tissue sample that provides more detailed information. Some situations require an endoscopic biopsy during procedures such as a colonoscopy or bronchoscopy, while others may need a surgical biopsy if the tissue cannot be reached safely with a needle.

Although the procedure itself usually takes only a short time, the information it provides is often the most important step in planning cancer treatment.

Why Doctors Cannot Treat Cancer Without A Biopsy

Modern cancer treatment is far more personalised than it was even a decade ago. Today, doctors need much more than imaging scans to decide the best treatment.

A biopsy answers several critical questions. It confirms whether the abnormal growth is actually cancer, identifies the exact type of cancer, shows how aggressive the tumour appears under the microscope and provides tissue for specialised laboratory tests.

These tests can reveal hormone receptors, genetic mutations and biomarkers that determine whether a patient may benefit from targeted therapy, immunotherapy or hormone therapy. This approach, known as precision oncology, allows treatment to be tailored to the individual rather than using the same medicines for everyone.

Dr Malhotra emphasised this point, saying, "The diagnosis is not the danger. The delay is. Biopsy helps precision oncology. It helps deciding the treatment approach. Without this we would be treating in the dark."

In other words, a biopsy is not simply about confirming cancer, it helps doctors choose the most effective treatment while avoiding therapies that are unlikely to work.

Can Scans Replace A Biopsy?

Many people assume that if a CT scan, MRI or PET-CT scan strongly suggests cancer, there is no need for a biopsy.

However, imaging tests and biopsies serve different purposes.

Scans can show the size, shape and location of an abnormal growth and whether cancer has spread to other organs. They can strongly suggest cancer, but they usually cannot confirm exactly what type of tumour it is or reveal its molecular characteristics.

Only a biopsy provides the tissue needed for laboratory analysis. In some cancers, this information determines whether a patient receives immunotherapy, targeted medicines, hormone therapy or chemotherapy.

According to a study published in the journal Frontiers in Molecular Biosciences, newer technologies such as liquid biopsy are also helpful as they look for fragments of tumour DNA in the blood. They are becoming increasingly useful in some situations; however, they currently complement rather than replace tissue biopsy for most patients.

Can A Biopsy Really Make Cancer Spread?

The fear that a biopsy spreads cancer did not arise out of nowhere. It is linked to a genuine scientific phenomenon called needle-tract seeding.

Dr Malhotra explained:
"These phenomena say that a few tumour cells may be displaced along the path of the biopsy needle. However, this event is extremely uncommon and should not be confused with cancer spreading. Seeding is not the same as spreading. A few displaced cells sitting in a needle track are not a metastasis."

Cancer metastasis occurs when cancer cells successfully travel through the blood or lymphatic system, survive the body's defences, establish themselves in a new organ and continue multiplying. This is a highly complex biological process.

Needle-tract seeding, on the other hand, refers only to the possibility that a very small number of cells may be displaced along the path of the biopsy needle. These cells do not automatically develop into new tumours, nor do they behave like metastatic cancer.

Experts say the two processes are fundamentally different and should never be confused.
Even the American Cancer society suggests that cancer spread through a biopsy is extremely rare.

What Happens If A Few Tumour Cells Are Displaced?

Even in the rare event that a few cells are displaced during a biopsy, this does not mean they will survive or grow.

Dr Malhotra explained that these cells are usually removed when the tumour is surgically excised. In addition, treatments such as radiotherapy and systemic anti-cancer therapy, along with the body's own immune system, can eliminate any remaining cells.

This is one of the reasons why doctors continue to recommend biopsies as the safest and most reliable way to diagnose cancer. The potential benefits of obtaining an accurate diagnosis and selecting the right treatment far outweigh the extremely small theoretical risk associated with needle-tract seeding.

Why Does This Myth Continue To Persist?

If we talk specifically about the Indian context, in many tier-two and tier-three cities, it takes two to three weeks to reach the final report to the treating doctor. During that period, the untreated cancer continues to grow naturally. The patient does not see natural history. He sees cause and effect. The biopsy happened; the lesion grew. The conclusion writes itself, and it is wrong.

In reality, cancer does not stop growing while laboratory tests are being carried out. Some tumours continue to enlarge or become more painful because of their natural progression. Since these changes occur soon after the biopsy, patients often assume the procedure caused the cancer to spread, when in fact the disease was already advancing.

Scientific Evidence

The reassuring news is that decades of research involving thousands of patients have consistently found that diagnostic biopsies do not increase the risk of cancer recurrence or reduce survival.

Published studies estimate that needle-tract seeding is extremely uncommon. A 2015 systematic review reported an overall incidence of less than one per cent. More recent reviews, including a 2024 analysis of breast needle biopsies published in the journal ‘Cancers’ found no evidence that undergoing a diagnostic biopsy increases the likelihood of cancer returning or shortens long-term survival.

These findings have strengthened international recommendations that biopsy should remain the standard method for confirming cancer before treatment begins.

Today, millions of biopsies are performed safely around the world every year, allowing doctors to diagnose cancers accurately and begin the most appropriate treatment without unnecessary delay.

Delaying a Biopsy: The Real Danger

Cancer is generally easier to treat when detected early. As it grows, it can invade nearby tissues, spread to lymph nodes or distant organs, and limit the range of treatment options available.

A patient who might initially have needed only surgery could later require chemotherapy, radiotherapy or more extensive operations because the disease has progressed during the delay.

Dr Malhotra emphasised, "The diagnosis is not the danger. The delay is."
The impact of delayed diagnosis is clearly seen in oral cancer. According to research published in the journal ‘Frontiers in Oral Health’, patients diagnosed while the disease is still confined to its original site have a five-year survival rate of nearly 79 per cent. Once the cancer spreads to distant organs, survival falls to around 19 per cent. Unfortunately, almost two-thirds of oral cancer patients in India are still diagnosed at an advanced stage, when treatment becomes more difficult, and outcomes are poorer.

These figures highlight why postponing a biopsy out of fear can have serious consequences.

Final Word

A biopsy remains the gold standard for diagnosing cancer because it provides the detailed information doctors need to confirm the disease and choose the most effective treatment. While the idea that a biopsy spreads cancer continues to circulate, decades of scientific evidence show that this fear is largely based on misunderstanding rather than medical fact. Needle-tract seeding is extremely rare and is not the same as cancer metastasis. Modern surgery, radiotherapy, systemic treatments, and the body's immune system further reduce any potential risk. The greater danger lies in delaying a biopsy until the cancer has progressed to a more advanced stage.