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🩺 Medically reviewed by the Health Decoded Guide Editorial Team · Last reviewed: August 2026
🔍 Quick Summary
Cancer is a group of diseases in which abnormal cells grow and divide without normal control. These cells may damage nearby tissues and, in some cancers, spread to other parts of the body.
There are many different types of cancer, and having cancer does not automatically mean it cannot be treated. Many cancers can be treated successfully, particularly when detected early.
1️⃣ Introduction
Your body is made up of trillions of cells. Normally, cells grow, divide and die in a carefully controlled way.
Cancer develops when some cells stop following these normal controls.
• abnormal cells continue growing when they should stop
• damaged cells may survive instead of dying
• these cells can build up and interfere with healthy tissues
👉 Cancer is not one single disease—there are more than 100 different types.
2️⃣ What happens to cells in cancer?
Healthy cells contain instructions that control when they should grow, divide, repair themselves and die.
Cancer cells behave differently.
• changes occur in the DNA that controls cell behaviour
• abnormal cells begin multiplying without normal control
• the body's usual systems for removing damaged cells may fail
Over time, these abnormal cells can accumulate.
👉 Cancer begins when the normal rules controlling cell growth and survival break down.
3️⃣ Are all cancers the same?
No. Cancer can begin in almost any part of the body.
Solid cancers
• may form masses called tumours
• examples include breast, lung, prostate and bowel cancers
Blood cancers
• begin in blood-forming tissues or immune cells
• examples include leukaemia, lymphoma and multiple myeloma
👉 Not every cancer forms a solid tumour, and different cancers can behave very differently.
4️⃣ What can increase the risk of cancer?
Cancer usually develops because of changes in the DNA of cells. These changes can happen for many reasons.
Lifestyle and environmental factors
• tobacco
• alcohol
• ultraviolet radiation from sunlight
• certain infections and harmful environmental exposures
Other factors
• increasing age
• inherited genetic changes
• random changes that happen when cells divide
👉 Cancer rarely has one simple cause. Usually, several factors influence whether it develops.
5️⃣ Possible symptoms
Cancer symptoms depend on where the cancer begins and how it affects the body.
Possible symptoms include:
• a new or changing lump
• unexplained weight loss
• unusual bleeding
• persistent changes in bowel or bladder habits
• a cough that does not go away
• unexplained persistent pain
• unusual or persistent tiredness
👉 These symptoms are commonly caused by conditions other than cancer—but persistent or unexplained changes should be checked.
6️⃣ What problems can cancer cause?
Cancer can affect the body in different ways.
• a tumour may press on nearby organs
• cancer cells may damage healthy tissues
• some cancers interfere with normal blood-cell production
• cancer may spread to other parts of the body
• illness and treatment may cause fatigue, pain or weight changes
👉 The effects depend greatly on the type, location and stage of the cancer.
7️⃣ 🩺 When should you seek medical attention? 🚨
Arrange medical assessment if you notice:
• a new lump or swelling that persists
• unexplained bleeding
• unexplained weight loss
• a persistent change in your normal bowel or bladder habits
• a symptom that is unusual for you and does not improve
Seek urgent medical care for severe symptoms such as major bleeding, severe breathing difficulty or sudden serious deterioration.
👉 These symptoms may indicate:
• cancer or another medical condition that needs investigation
• need for appropriate medical assessment
8️⃣ Can cancer be treated?
Yes. Cancer treatment has improved considerably, and many cancers can be treated successfully.
Depending on the cancer, treatment may include:
• surgery
• chemotherapy
• radiotherapy
• immunotherapy
• targeted therapy
• hormone therapy
Some people need one treatment, while others need a combination.
👉 Cancer treatment is increasingly personalised according to the type and characteristics of the cancer.
9️⃣ How is cancer diagnosed?
The exact investigations depend on the suspected type of cancer.
They may include:
• physical examination
• blood or urine tests
• imaging such as ultrasound, CT or MRI
• endoscopy for certain organs
• biopsy to examine tissue under a microscope
👉 A biopsy is often needed to confirm whether abnormal cells are cancerous.
🟢 Important Message
A cancer diagnosis can feel frightening, but cancer is not automatically a death sentence.
Treatment and survival vary greatly between different cancers, and advances in early detection and treatment mean many people recover completely or live for many years with their cancer controlled.
👉 Recognising unusual changes and seeking medical advice early can make an important difference.
FAQ
• Is cancer one disease?
No. Cancer describes a large group of diseases involving abnormal, uncontrolled cell growth.
• Does every tumour mean cancer?
No. Tumours can be benign (non-cancerous) or malignant (cancerous).
• Can cancer spread to other parts of the body?
Yes. Some cancer cells can spread through the blood or lymphatic system. This is called metastasis.
• Can cancer be cured?
Some cancers can be cured, particularly when detected early. Others can be controlled for many years with treatment.
🧠 Why We Delay
Fear is one of the biggest reasons people delay getting possible cancer symptoms checked. Some avoid medical care because they worry that finding cancer means there will be nothing doctors can do. Others normalise symptoms, feel embarrassed or hope they will disappear.
Many suspicious symptoms turn out not to be cancer, and when cancer is present, earlier diagnosis can sometimes provide more treatment options and improve outcomes.
👉 Getting a symptom checked does not mean you have cancer—it means you are giving yourself the chance to find out what is happening.
🔗 Related Health Topics
• How Cancer Develops
• What Causes Cancer?
• Benign vs Malignant Tumours
• How Cancer Spreads
• Cancer Warning Signs
📚 Medical References
• World Health Organization (WHO). Cancer.
• National Cancer Institute (NCI). What Is Cancer?
• National Health Service (NHS). Cancer.
• American Cancer Society. What Is Cancer?
• Cancer Research UK. What is cancer?
⚠️ Medical Disclaimer
This article is for educational purposes only and does not replace professional medical advice.
If you have concerning symptoms, risk factors or abnormal test results, consult a healthcare professional.