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What is Cancer?

When people hear the word cancer, lots of different words, emotions and experiences comes to mind. But today we are here to explore the facts about what cancer is, how it is caused, and the information you need to know about catching it early.

What is cancer?

So first, what is cancer? Cancer is defined as an uncontrolled division of normal cells that become abnormal in a part of the body affected or even throughout the body. But what does that mean?

Our body’s cells are designed to divide and regenerate. That is normal. Cancer occurs when abnormal or changed cells divide and spilt too quickly and in some cases, spread and lodge themselves in other parts of the body. These growing cell clusters are known as tumours .

It is important to know that not all tumours are cancerous. Some tumours that develop in the body do not contain cancer cells, and these are known as benign tumours. When we talk about cancer, you will hear the word malignant, and that means that the tumour in the body contains cancerous or pre-cancerous cells and will need to be treated by a medical professional. If cells move from one place to another in the body and lodge themselves elsewhere this is known as cancer spread or metastases.

What are the most common symptoms of cancer?

This would be difficult to say outright as it depends on what part of the body we are talking about, so it is important to talk about signs and symptoms in that context.

Depending on where the cancer resides in your body, you may experience different warning signs and symptoms. This is why education around Ireland’s most common cancers is so important.

For example, for breast cancer, a common sign may feel a lump in the breast tissue or you may see dimpling which looks different for you. For melanoma, the warning sign can be a new or changing mole. However, every cancer diagnosis is different, and there is no one size fits all when it comes to signs and symptoms. It is really important to know your body in the first instance so that you can notice changes if and when they happen so that you and go and do something about them early.In broad strokes the three main categories you should be looking out for are:

Unexplained changes:

This accounts for a new change in your body such as a lump, swelling, weight loss without trying, a bleed that isn’t usual for you or a pain that has developed and isn’t going away.


Persistent Changes:

These are changes you notice in your body that occur and do not go away such as a cough that lasts longer than 3 weeks, persistent bloating, a sore that doesn’t heal and changes to your usual digestions such as ongoing heartburn, indigestion or difficulty swallowing.


Unusual Changes:

These are changes that occur over time. These could be a change in your bowel and bladder habits or a new or changing mole. With unusual changes as well as unexplained and persistent changes, if you notice something that is not normal for you, you should always consult your GP.

The most important thing to be aware of is your overall health, and to listen to your body and identify what is normal for you. That way, if you do notice a change, you can seek help early. For more information on the most common signs and symptoms of cancer, click here.

What causes cancer?

Biologically, what causes cancer is a change or mutation in the DNA of your cell. Your DNA works as a kind of information highway, telling your cells which function they need to carry out. When this DNA is mutated or changed, the cell doesn’t know what to do, and so begins to divide, grow and change in every direction. This is what causes cancer.

For some, cancer risk is determined by genetic or hereditary conditions. These gene mutations are passed down from generation to generation and can increase your risk of developing cancer in the future. Examples of these type of conditions include:

For others, there are outside stimuli or risk factors that increase your bodies risk of developing cancer. These risk factors include:


While this may seem frightening, the good news is that between 30-50% of cancer diagnoses can be prevented through small but impactful changes to our daily routine. For more information on these changes and how you can reduce your risk, click here.

At the Marie Keating Foundation our vision is to create a world free from the fear of cancer and we strongly believe no one should have to face a cancer diagnosis alone. It can be a difficult and daunting time if you or a loved one hears those words ‘you have cancer’ but with early detection, better treatment options and the right support, more and more people are coming out the other side of cancer. To download free copies of our cancer awareness and prevention publications, click here.

If you are currently on a cancer journey and would like some support, you can take a look at our free cancer services here.