What Tests Are Done to Diagnose Lung Cancer

In reality, there is rarely a single test that provides the full answer. Diagnosis usually develops in stages. Imaging scans first identify something abnormal. Further investigations then confirm whether cancer is present and, if so, what type it is.

That process matters. The tests do more than confirm a diagnosis. They help us understand the behaviour of the cancer and decide what treatment may work best.

Chest X-Ray: Often the First Step

For many people, the process begins with a chest X-ray.

This is a simple scan that produces an image of the lungs and surrounding structures. It allows us to look for visible abnormalities such as masses, fluid around the lungs, or areas where lung tissue appears altered.

To be honest, an X-ray alone cannot diagnose lung cancer. Many conditions can create similar appearances. Infection, scarring, or inflammation can sometimes look suspicious on a scan.

But it can provide an early clue.

In some cases, lung cancer is detected incidentally. A patient may undergo an X-ray for a persistent cough or chest discomfort, and something unexpected appears. According to research, around 48,000 people are diagnosed with lung cancer each year in the UK.

If an X-ray raises concern, more detailed imaging usually follows.

CT Scans: Understanding What the Scan Shows

The next step is often a CT scan of the chest.

CT imaging produces detailed cross-sectional pictures of the lungs. This allows us to see the exact location of an abnormality, its size, and whether nearby lymph nodes may be involved.

I mean, this is often the point where the situation becomes clearer. A CT scan can show whether something that looked concerning on an X-ray truly requires further investigation.

It also helps us, doctors, decide how to obtain a biopsy safely if needed.

These findings help guide the next stage of care. In practice, they form the basis of our private treatment plan for lung cancer, where the tumour’s size, position, and any lymph node involvement are considered together before treatment decisions are made.

PET-CT Scans: Checking for Spread

If a CT scan suggests lung cancer, a PET-CT scan may be recommended.

This investigation combines two different types of imaging. The CT component provides detailed structural pictures of the body. The PET scan detects areas of increased metabolic activity.

Cancer cells often absorb more of the radioactive sugar that is used during PET scanning. These areas then appear highlighted on the scan.

You know, this can reveal whether cancer has spread beyond the lungs. Nearby lymph nodes or distant organs sometimes show activity that requires further investigation.

Understanding whether the disease is confined to the lung or has spread elsewhere is essential. Treatment decisions depend heavily on this information.

Bronchoscopy and Endobronchial Ultrasound

Imaging can suggest cancer, but it cannot confirm it. A tissue sample is usually required.

One common method is bronchoscopy. A thin flexible camera is passed through the mouth into the airways. This allows the bronchial tubes to be examined directly and small tissue samples to be collected from suspicious areas.

Sometimes an additional technique called endobronchial ultrasound is used.

Endobronchial ultrasound, often shortened to EBUS, combines bronchoscopy with ultrasound imaging. It allows us to locate lymph nodes near the airways and collect tissue samples with a fine needle.

That information is important when assessing whether cancer has spread to lymph nodes in the centre of the chest. It helps us stage the disease accurately before treatment begins.

Needle Biopsy: Confirming the Diagnosis

Not all tumours can be reached through bronchoscopy.

If the abnormal area sits deeper in the lung, a CT-guided needle biopsy may be performed. A fine needle is carefully inserted through the chest wall into the suspicious area while CT imaging guides the procedure.

The collected tissue is then analysed in the laboratory.

This step confirms the diagnosis. It also determines the exact type of lung cancer present.

Most cases fall into two main categories. Non-small cell lung cancer accounts for roughly 85 percent of diagnoses. Small-cell lung cancer is less common but tends to grow and spread more rapidly.

Identifying the specific type is essential before making treatment decisions.

Molecular Testing: Looking at the Tumour More Closely

Once cancer has been confirmed, further laboratory testing often follows.

Molecular testing examines the genetic characteristics of the tumour cells. These tests look for specific mutations or protein markers that may influence treatment choices.

Examples include EGFR mutations, ALK rearrangements, and PD-L1 expression.

It’s bloody hard to overstate how important this has become in modern oncology. These results can identify patients who may benefit from targeted therapies or immunotherapy.

In other words, treatment can be tailored to the biology of the tumour rather than relying solely on traditional chemotherapy.

Blood Tests and Additional Scans

Blood tests do not diagnose lung cancer on their own, but they remain an important part of the overall assessment.

They help evaluate organ function, including the liver and kidneys, which can influence which treatments can be given safely. Blood tests may also reveal signs of infection, inflammation, or anaemia, all of which can affect treatment planning.

Additional imaging may also be required depending on the findings from earlier scans. For example, MRI scans of the brain are sometimes used to check whether lung cancer has spread to the central nervous system. In certain situations, bone scans or further CT imaging may also be recommended to assess whether the disease has spread beyond the chest.

Each investigation adds another piece to the picture. Gradually, the diagnostic pathway moves from uncertainty to clarity, allowing treatment decisions to be made with greater confidence.

About Dr. James Wilson

Dr. James Wilson is a consultant clinical oncologist specialising in lung cancer and thoracic cancers. His practice focuses on helping patients access investigations quickly and move towards a clear treatment strategy.

Based in a full-time private practice in Central London, he supports patients through diagnosis and treatment planning, aiming to ensure that decisions are informed, timely, and carefully considered.