The words tumour and cancer are often used interchangeably, but they don’t mean the same thing. Even in medical settings, the terms can be blurred by vague language, leaving patients confused about what’s really going on in their bodies.
Understanding the difference is important — not just for clarity, but for making informed decisions about health and treatment.
What exactly is a tumour?
A tumour simply refers to an abnormal growth or lump of tissue. Tumours can form almost anywhere in the body, including muscle, fat, bone, nerves, blood vessels, or glands.
Crucially, not all tumours are cancer.
There are two broad categories:
- Benign tumours – These are not cancerous. Some are harmless and may never need treatment, such as lipomas (fatty lumps under the skin) or haemangiomas (clusters of blood vessels often seen at birth).
- Malignant tumours – These are cancer. They have the ability to grow aggressively, invade nearby tissues, and spread to other parts of the body.
Even benign tumours can cause serious problems depending on where they develop. For example, uterine fibroids can trigger heavy bleeding, while benign brain tumours may interfere with hormone production or vision, sometimes requiring surgery.
So, what is cancer?
Cancer begins when normal cells develop genetic changes (mutations) that allow them to grow uncontrollably and avoid the body’s natural defence systems.
What sets cancer apart is its behaviour. Cancer cells can:
- Grow without limits
- Invade surrounding tissues
- Spread to distant organs (a process called metastasis)
These abilities are what make cancer dangerous.
Many cancers form solid masses — such as breast, lung, or skin cancers — which is why they’re often described as tumours. But not all cancers form lumps. Blood cancers like leukaemia circulate in the bloodstream and usually don’t create a mass at all.
How are tumours and cancer detected?
Both benign and malignant tumours can show up as lumps noticed by a person or discovered during medical tests for symptoms like pain, difficulty swallowing, or unexplained bleeding.
Doctors may use:
- Imaging tests such as ultrasound, CT scans, or MRI
- Biopsies, where a small tissue sample is examined under a microscope
A pathologist then determines whether the cells are benign or malignant — a key step in deciding treatment.
How are they treated?
Sometimes treatment looks similar. Surgery, for example, may be used to remove both a benign brain tumour and a skin cancer.
But cancer treatment is often more complex and urgent because of the risk of spread. Depending on the type and stage, cancer care may involve:
- Surgery
- Radiotherapy
- Chemotherapy or other systemic treatments that affect the whole body
Benign tumours, on the other hand, may simply be monitored if they’re not causing harm.
Why using the right words matters
The word cancer carries fear — often linked to severe illness or death — even though many cancers today are treatable or curable, especially when caught early.
When doctors use vague terms like mass, spot, or lesion instead of clearly saying cancer, patients may misunderstand the seriousness of their condition. Studies show that many people don’t realise a doctor is talking about cancer unless the word is used directly.
Clear language helps patients:
- Understand their diagnosis
- Ask the right questions
- Make informed choices about treatment
In short
- A tumour is an abnormal growth
- Cancer is a disease caused by malignant cells
- All malignant tumours are cancers
- Not all tumours are cancer
- Not all cancers form tumours
Knowing the difference empowers patients — and reminds healthcare providers that clarity isn’t just good communication, it’s good care.
