What is Lung Cancer?

Lung cancer is a type of cancer that occurs in the lungs, two vital organs in your chest that take in oxygen when you inhale and release carbon dioxide when you exhale.

As the cancer grows it forms a tumour. A tumour that starts in the lung is known as a primary lung cancer. Tumours in the lung may also originate from cancer cells that have spread through the blood stream from another part of the body such as the breast, bowel, or prostate – these cancers are called lung “secondaries” or “metastases” also known as secondary lung cancer.

These lung tumours can then cause a blockage and result in symptoms, for example, difficulty in breathing, wheeze or coughing up blood. Often symptoms of lung cancer may not occur until a very late stage of disease progression. Therefore, screening asymptomatic individuals that fall into the high-risk category of developing lung cancer is crucial. LungCheck offers this service.

Introducing Lung Cancer Screening will Save Lives

More people die from lung cancer in Ireland than any other type of cancer as disease is only identified when people are symptomatic. Individuals are often asymptomatic in the early stages of lung cancer. Many individuals are diagnosed with lung cancer (the leading cause of cancer death in Ireland in both women and men) when the disease is in the later stages and is incurable. Screening individuals at increased risk of developing lung cancer before symptoms begin can turn this picture round.

Currently in Ireland, there is no publicly funded national lung cancer CT screening service. Specialist Screening Healthcare Ireland created LungCheck, a consultant specialist led lung cancer CT screening service offering annual low-dose CT (LDCT) for individuals at increased risk of developing lung cancer. The LungCheck service is offered privately in the absence of a publicly funded service. Specialist Screening Healthcare Ireland aim to collect Irish data to support any future European or HSE directives to implement a national lung cancer screening service in Ireland.

There is clinical evidence that screening people based on their risk of developing lung cancer saves lives. The LungCheck service aims to detect lung cancer disease at its earliest and most treatable stage before symptoms begin. Research has shown that using LDCT scans to screen individuals at higher risk of lung cancer saved more lives compared to chest x-rays. For higher risk individuals, receiving yearly LDCT scans before symptoms start helps lower the risk of dying from lung cancer.

LungCheck launched by Specialist Screening Healthcare Ireland is the first lung cancer screening service in Ireland to partner with consultant pulmonary radiologists who have a special interest in lung cancer to offer dual CT reporting. LungCheck, Ireland’s premier lung screening service offers two CT reports to include a specialist Supplementary CT Report as well as access to multidisciplinary meetings to support best practice as per international lung cancer screening guidelines.

There are challenges in access to lung cancer diagnostics and treatment across Europe. We are not sufficiently improving the rates of early diagnosis of lung cancer in Europe. Numerous health experts have come together including the Irish Cancer Society to support the European Respiratory Society issuing an open letter to urge MEPs in the European Parliament to set a target to increase early lung cancer diagnosis and detection by 20% by 2030 as part of Europe’s Beating Cancer Plan. Specialist Screening Healthcare Ireland ‘s LungCheck service supports this campaign.

Know the Types of Lung Cancer

The type of lung cancer you have tells you the type of cell that the cancer started in. The stage of a lung cancer or how much it has spread helps inform treatment decisions and prognosis. Stage indicates how big the tumour is, whether it has invaded local tissues outside of the lungs including lymph nodes, and whether it has spread to other distant sites in your body.

Because the lungs are large, tumours can grow in them for a long time before they are detected. Even when symptoms of lung cancer occur, people think this is due to other reasons. For this reason, Specialist Screening Healthcare Ireland’s LungCheck service supports lung cancer screening with a CT as early-stage lung cancer (stages I and II) is difficult to detect without the appropriate diagnostic tests.

1. Primary Lung Cancer

There are 2 major types of primary lung cancer. The most frequent type is Primary Non-Small Cell Lung Cancer however, the most aggressive is Primary Small Cell Lung Cancer.

Primary Non-Small Cell Lung Cancer (NSCLC)

There are four main types of non-small cell lung cancer (NSCLC):

  1. Adenocarcinoma
    Formed in the glands that secretes mucus which line the airways. It is the most common type of lung cancer in people who have never smoked.
  2. Squamous Cell Carcinoma
    This type of cancer usually begins in the bronchi (the passages that lines the inside of the airways and brings air into the lung) and grows more slowly than other main forms of lung cancer.
  3. Large Cell Carcinoma
    This cancer may begin anywhere in the lungs and tends to grow quickly.  When viewed under the microscope, the cells appear large and round.
  4. Not Otherwise Specified (NOS)
    This occurs when the pathologist cannot diagnose for certain which type of non-small cell lunger cancer you have.

Some non-small cell lung cancers can be connected to genetic changes called mutations that can be either genetically inherited or acquired through changes in the activity of the cells that cause cancer to develop. Molecular analysis of biopsies looking for specific mutations is useful in directing treatment plans.

Primary Small Cell Lung Cancer (SCLC)

Primary small cell lung cancer develops in cells around the bronchi (airways) called neuroendocrine cells (NETs). 

This type of lung cancer is the most aggressive, often fast-growing and can spread quickly generally to lymph nodes and other parts of the body such as your bones, brain, adrenal glands and liver.

2. Secondary Lung Cancer or Metastatic Lung Cancer

Secondary lung cancer, also called a metastasis is when a cancer that started somewhere else in the body has spread to the lung. 

A secondary cancer in the lung is made of the same type of cells as the primary cancer. Cancer cells can separate from a tumour and travel through the blood or lymph system to the lung. For example, if breast cancer spreads to the lungs, it would be called breast cancer with metastases to the lungs, or breast cancer with lung metastases. It would not be called lung cancer as they are cancerous breast cells, not cancerous lung cells. This is stage IV breast cancer. 

What are the Stages of Lung Cancer?

The stage of a cancer tells you how big it is and whether it has spread. The stage dictates treatment options and prognosis.

Individuals are often asymptomatic in the early stages of lung cancer. Symptoms of lung cancer usually present when the disease has progressed towards more advanced stages of the disease. Therefore, screening for lung cancer in Ireland may play an instrumental role in increasing lung cancer survival rates due to early detection.

Specialist Screening Healthcare Ireland’s LungCheck service hopes to detect lung disease in Ireland at its earliest and most treatable stage when lung cancer has just started to develop but before symptoms begin.

1. Staging for Primary Non-Small Cell Lung Cancer (NSCLC)

TNM Cancer Staging System

TNM staging is an international cancer staging system used to describe the extent of a cancer in a patient’s body. 

TNM stands for Tumour, Node, Metastasis and is the most common method used by specialists to stage for primary non-small cell lung cancer. 



Tumour describes the size of the original primary tumour (area of cancer) and how deeply has the tumour has grown into the lungs.



Node (N) describes whether the cancer has spread to the lymph nodes.



Metastasis (M) describes whether the cancer has spread to other parts of the body.

TNM Classification in Lung Cancer

The 8th Edition of TNM in Lung Cancer is the standard of non-small cell lung cancer staging since January 1st, 2017. It is issued by the International Association for the Study of Lung Cancer (IASLC).

Modifications to the TNM 7th edition are marked in orange.
Numbered Cancer Staging System

As noted in the TNM classification system, the overall cancer stage is determined after the cancer is also assigned a letter or number 0,1,2,3,4 after each T,N or M letter.  The lower the stage number, the less advanced the cancer is and the better the outcome is likely to be; the higher the stage number, the more advanced the cancer is. 

Occult or Hidden Cancer

Cancer cells can be picked up in the mucus you cough up. At this earliest stage your tumour cannot be seen on imaging scans or a biopsy. The occult stage is also called “hidden cancer”.

Stage 0 or Carcinoma in situ (CIS)

Abnormal cells are present but have not spread to nearby tissue, also called carcinoma in situ (CIS). It is not cancer but may develop into cancer.

Lung Cancer Stage 1 or Localised Disease

Early cancer confined to one lung without lymph node spread. Cancer is limited to the place where it started inside the lungs (localised).

Lung Cancer Stage 2 or Regional Disease

Still an early stage of cancer with limited regional spread (usually within the same lung or nearby lymph nodes).

Lung Cancer Stage 3 or Locally Advanced Disease

A more advanced cancer that is found in the lung and in the lymph nodes in the middle of the chest (larger tumour, more extensive disease, more distal lymph node involvement). Also described as locally advanced disease.

Lung Cancer Stage 4 or Distant or Metastatic Advanced Disease

This is the most advanced cancer stage that has spread beyond the lungs or chest. Also described as metastatic advanced disease. This is when the cancer has spread to both lungs, to fluid in the area around the lungs, or to distant parts around the body, such as your adrenal glands, brain, bones or liver.

Lung Cancer Recurrence

Recurrent lung cancer is lung cancer that has come back after treatment. If there is a recurrence, the cancer may need to be staged again (“restaged”) using the system described above.

2. Staging for Primary Small Cell Lung Cancer (SCC)

Limited Stage Small Cell Cancer

Limited stage small cell lung cancer is found in a single area on one side of the chest.

This generally means your cancer:

  • is only in one lung.
  • may have spread to lymph nodes on the same side of the chest and to the centre of the chest.
Extensive Stage Small Cell Cancer

Extensive stage small cell cancer is when the cancer has spread widely and from the original tumour. Most people with small cell lung cancer are diagnosed with extensive stage cancer because the cancer spreads early and quickly, before it causes symptoms.

This generally means your cancer may have spread:

  • within the chest (either to the other lung or to lymph nodes further away from the cancer).
  • to other distant parts of your body.
  • or there may be cancer cells in the fluid around the lung (a malignant pleural effusion).

What is Mesothelioma?

Mesothelioma is a rare cancer affecting the protective linings that cover the surface of your lungs and chest wall. Your mesothelium consists of a thin membrane of cells that functions to protect internal structures and aid in movement and breathing.

Mesothelioma cancer generally happens when someone is exposed to asbestos. It is important to note, mesothelioma is not a form of lung cancer as lung cancer develops inside the lungs.

Know the Symptoms of Lung Cancer

Individuals are often asymptomatic in the early stages of lung cancer. Symptoms of lung cancer usually present when the disease has progressed towards more advanced stages of the disease. Therefore, screening for lung cancer in Ireland may play an instrumental role in increasing lung cancer survival rates due to early detection. Testing for lung cancer when you have no symptoms but fall into the high-risk category is called lung cancer screening.

According to the Irish Cancer Society:

  • 62% of all lung cancers in Ireland present at a late stage (stage III or IV).
  • 2 out of 3 lung cancers are diagnosed at a late stage.
  • 1 in 4 lung cancers – that’s over 600 cases of lung cancer a year – are being diagnosed in Ireland in the emergency department.

LungCheck is a consultant specialist led premier lung cancer CT screening service launched by Specialist Screening Healthcare Ireland. The LungCheck service hopes to detect lung disease in Ireland at its earliest and most treatable stage when lung cancer has just started to develop but before symptoms begin. If you are at increased risk of developing lung cancer you should be screened.

Shortness of BreathShortness of Breath
Shortness of Breath

Breathlessness is a common symptom of lung disease, however many people put breathlessness down to ageing, being overweight or unfit. Everyone gets breathlessness sometimes, it is a natural response that your body needs more oxygen and energy when you do something that requires physical effort, such as running for a bus or exercising. However, unexplained breathlessness needs to be addressed.

Persistent CoughPersistent Cough
Persistent Cough

Coughing is very common. Most individuals will have episodes of lingering cough throughout their lives, but it can also be a symptom of many different medical conditions. A persistent cough is a cough that lasts for weeks, can interrupt your sleep and leave you feeling exhausted. Cough is one of the most common symptoms of lung cancer. If you have a persistent cough for more than three weeks, it is important to be screened. If you have a moist cough, your mucus becoming yellow, green or bloody, it is important you see a health professional as soon as possible.

Coughing Up BloodCoughing Up Blood
Coughing Up Blood

If you cough up blood, It is important to be screened.


Wheezing is a high-pitched whistling sound made while you breathe. It is generally heard when you breathe out (exhale) and is caused by narrowed airways or inflammation. Asthma and COPD are the most common causes of wheezing. However, it can be triggered for many other reasons, including a viral or bacterial respiratory infection. A slight wheeze may be the first signs of lung disease, including lung cancer.

Weight LossWeight Loss
Weight Loss

Unintentional weight loss is a sign of a serious issue, that should not be ignored. Weight loss can be a sign of respiratory disease, particularly lung cancer or severe Chronic Obstructive Pulmonary Disease (COPD). It is important to discuss any sudden, unexplained weight loss.


One of the most common symptoms of lung disease is fatigue. Fatigue is an excessive persistent feeling of tiredness that may not be alleviated by sleep or rest. It can affect the way you think, including poor concentration and memory loss, as well as make you feel more emotional than usual. Fatigue can also affect your ability to do everyday tasks such as taking a shower or making your dinner.

Chronic Chest PainChronic Chest Pain
Chronic Chest Pain

Chest pain is a symptom associated with many conditions. It can be a sign of a heart attack or cardiac condition but is also commonly related to lung disease. Chest pain should always be taken seriously, especially if it lasts for a month or more, or if it gets worse when you breathe in or cough.

Raspy Hoarse Voice Raspy Hoarse Voice
Raspy Hoarse Voice

Vocal cords create sound by vibrating open and closed, but lung cancer can affect the nerve that triggers this movement. A raspy hoarse change in your voice could indicate lung cancer. In lung cancer patients, hoarseness is more common in those with tumours to the left lung (due to the location of the left recurrent laryngeal nerve) and those who also have larynx cancer.

Persistent Chest InfectionsPersistent Chest Infections
Persistent Chest Infections

Chest infections that are repetitive and will not go away, even after antibiotics are common before lung cancer is diagnosed.

Who is at Increased Risk of Lung Cancer?

The benefits of lung cancer screening programmes are highly dependent on risk group definition. The US Preventative Lung Cancer Taskforce published their up-to-date 2021 recommendations of annual low dose CT in individuals over 50 years with a 20 pack-year history (20 cigarettes a day for 20 years).

Leading Risk Factors/Causes of Lung Cancer


Smoking causes about 9 in every 10 lung cancers. The risk increases with the amount of time you have smoked, the number of cigarettes you have smoked and if you started young (20 pack year history or 20 cigarettes a day for 20 years).

Passive Smoking

Inhaling other people’s cigarette smoke increases the risk of lung disease and cancer. But the risk is still much less than if you smoke yourself.

Risk by Age

Adults aged 50-74 years with a 20 pack-year history (20 cigarettes a day for 20 years) are offered lung cancer screening in other countries.


Certain chemicals such as asbestos, uranium, metal dust and fumes, nickel, paints, diesel exhaust, nitrogen oxides increases risk. These risks are even higher if you smoke as well.

Air Pollution

Air particle pollution emitted directly from wood stoves, forest fires, vehicles and other sources like power plants increases risk.

Check the EPA Air Quality Index for Health (AQIH) for the counties station nearest to you as shown on Ireland’s EPA air quality map.

In 2020, Dublin City Council launched their own county specific Dublin air quality map to allow people to check the air quality in their area. Dublin is the first Irish city to sign up to the global BreatheLife campaign, a commitment to meet WHO air quality guideline values by 2030. 

When you are travelling abroad we recommend checking the air quality of the country you are travelling to. Mobile air quality apps such as Aircare that are free to download can be very useful.

Radon Gas

Radon is a radioactive gas found naturally in the soil that causes lung cancer in individuals when exposed to high levels over a long period of time. It is formed in the ground by the radioactive decay of uranium which is present in all rocks and soils. You cannot see it, smell it or taste it. If your home traps it inside, it can build up and cause harm. Exposure to concentrated amounts of radon gas increases a person’s risk for developing primary small cell lung cancer. Every year in Ireland, radon causes about 300 cases of lung cancer.

Radon gas can only be measured with special detectors. Test kits that can detect and measure levels of radon are widely available. If you think you may be at risk, check the EPA Radon Map. You will find a map showing the counties in Ireland predicted to be at particular risk from radon, called high radon areas.

Family History

If you have a parent, brother or sister who has had cancer which started in their lung, your risk is doubled.

Genetic risk factors may predispose certain people to lung cancer. Individuals with an immediate family member who has or had lung cancer (and who does not or did not smoke) may be more prone to developing the disease. A family history of lung cancer may increase your non-small cell lung cancer (NSCLC) risk. Some evidence points toward a genetic link in a few cases. However, researchers have not determined whether shared environmental or behavioural factors, such as radon gas or smoking, play a greater role in a family’s history of lung cancer than genetics.

Diagnostics guided by Lung Cancer Screening based on International Clinical Trial Data

Specialist Screening Healthcare Ireland’s LungCheck service is guided by the data from many international clinical trials proving the importance of volume-based analysis of a pulmonary nodule following CT Screening.

The US National Lung Screening Trial (NLST) in 2002 demonstrated the benefits of low-dose computed tomography (LDCT) screening for lung cancer with a 20–43% reduction in  mortality. The US Preventative Lung Cancer Taskforce published their up-to-date 2021 recommendations of annual LDCT in individuals over 50 years with a 20 pack-year history (20 cigarettes a day for 20 years).

The results of the NELSON Trial (Dutch/Belgian randomised lung cancer screening trial) were published in the New England Journal of Medicine, showing LDCT scans reduces lung cancer mortality in men and women. The NELSON trial uses a “volume-based” principle, where the increase in volume of the lung nodule is measured over time. This volume doubling time (VDT) of a nodule is key to detecting a lung cancer, with a low false-positive rate of only 1.2%.

The UK Lung Cancer Screening (UKLS) pilot was so successfully undertaken, that NHS England have established Targeted Lung Health Checks to review their population based results.

Lung cancer screening with annual LDCT reduces the number of deaths from lung cancer in higher risk patients. Research has shown that using low-dose CT (LDCT) scans saves more lives when compared to using chest x-rays alone. CT scanning is painless and non-invasive. No contrast material is required for LDCT. No radiation remains in a patient’s body after a CT examination. 

What does the LungCheck Screening Service for Lung Cancer Involve?

  • Lung Cancer Risk Assessment Prediction Score – (Spitz, LLP, Hoggart and PLCO) Lung Cancer Risk Models
  • CT Chest Screening – Guided by International Clinical Trial Data
  • Dual Consultant Radiologist Specialist Reporting
    Includes a Supplementary Specialist Screening LungCheck CT Report.
  • Multidisciplinary Meeting (MDM), if clinically indicated
    If a clinical concern is raised during your LungCheck assessment and our certified specialist lung radiologist reports an abnormality on your CT Chest scan your case will then be listed at an MDM. Treatment plans are collaboratively developed to ensure you will be referred to the right specialist who will be able to provide your treatment or the recommendation may be to continue with a LDCT surveillance approach.
  • Education on Smoking Cessation Supports +/- Onward Referral to Smoking Cessation Specialist
    The best way to prevent lung cancer is to never smoke or stop smoking now.
  • Education on Exercise for Wellness +/- Onward Referral to Pulmonary Rehabilitation
    Staying active and undertaking light exercise has been shown to help better tolerate, respond to and recover from lung cancer treatments, such as chemotherapy, radiotherapy and surgery.
  • Education on Counselling Supports +/- Onward Referral
    To help you cope better with the many difficulties you may face, including during and after a lung cancer diagnosis.

Are you at increased risk of developing lung cancer?

Consider LungCheck with Specialist Screening Healthcare Ireland.

It is important to note, a lung cancer screening does not prevent lung cancer, but it may detect cancer before an individual develops symptoms of the disease.