What Does Lung Cancer Look Like on CT?

What is the difference between a nodule and a mass?

A pulmonary nodule is a relatively small focal opacity within the lung.

Traditionally, lesions up to approximately 3 cm are described as nodules, while larger lesions are generally described as masses.

But size alone does not determine whether something is malignant.

A tiny lesion can occasionally represent early cancer.

A larger lesion can occasionally be benign.

What does a suspicious lung nodule look like?

Radiologists consider several characteristics.

These include:

• —size
• —shape
• —margin
• —density
• —growth
• —location
• —calcification pattern
• —relationship to surrounding structures.

Certain appearances increase suspicion but are not diagnostic on their own.^[3,4]

What is spiculation?

A spiculated nodule has lines extending from its margin into the surrounding lung.

It can look irregular or star-like.

Spiculation increases concern for malignancy and is an established component of pulmonary-nodule risk assessment.

What does “lobulated” mean?

A lobulated lesion has a scalloped or irregular contour rather than being perfectly round.

Lobulation can increase suspicion in the appropriate setting, particularly when combined with:

• —increasing size
• —spiculation
• —other suspicious features.

Again, morphology needs to be considered as a whole.

Is a smooth round nodule always benign?

No.

Smooth margins may be reassuring in some contexts, but cancers can occasionally have relatively smooth borders.

Likewise, many benign nodules are smooth.

No single CT feature should be interpreted in isolation.

What is a ground-glass nodule?

A ground-glass nodule is an area of increased lung density through which underlying vessels remain visible.

Ground-glass abnormalities have many potential causes, including:

• —inflammation
• —infection
• —fibrosis
• —haemorrhage
• —pre-invasive or early adenocarcinoma-spectrum disease.

Transient ground-glass nodules may disappear.

Persistent ground-glass nodules require assessment according to their:

• —size
• —growth
• —morphology.

Some very early lung adenocarcinomas can remain predominantly ground glass for prolonged periods.

What is a part-solid nodule?

A part-solid nodule contains:

• —a ground-glass component
• —a more solid component.

Persistent part-solid lesions receive particular attention because the size and growth of the solid component can be associated with invasive disease.

This does not mean every part-solid lesion is cancer.

Can lung cancer contain calcium?

Yes.

Calcification is often associated with benign pulmonary nodules, particularly when it has certain classic patterns.

However, the presence of calcium does not universally prove that a lesion is benign.

Radiologists assess the pattern rather than simply asking whether calcium is present.

Why is growth important?

Cancer cells divide over time.

Demonstrating that a pulmonary nodule is enlarging can therefore increase concern.

This is why comparison with older scans is so valuable.

Radiologists may compare:

• —current CT
• —previous CT
• —CT coronary angiography
• —PET-CT
• —CT abdomen including the lung bases.

Sometimes a scan performed several years earlier contains the most useful information.

What is volume doubling time?

Modern pulmonary-nodule assessment can use software to measure nodule volume.

The volume doubling time — VDT — estimates how quickly the volume of a nodule is increasing.

Growth rate forms part of several modern lung-nodule and lung-screening pathways.

Very slow or absent growth may be reassuring in certain types of nodule, although subsolid lung cancers can grow much more slowly than many solid cancers.

Can lung cancer block an airway?

Yes.

Centrally located lung cancers can grow close to or within the major bronchi.

They may cause:

• —airway narrowing
• —complete bronchial obstruction
• —collapse of part of the lung
• —recurrent infection behind the obstruction.

A patient may therefore initially be investigated because of persistent or recurrent pneumonia.

What is atelectasis?

Atelectasis means loss of volume or collapse of part of the lung.

There are many benign causes.

But when a central tumour obstructs an airway, the lung beyond that obstruction may collapse.

CT can help identify the cause of the collapse.

Can lung cancer look like pneumonia?

Sometimes.

Certain lung cancers can produce consolidation or pneumonia-like appearances.

Conversely, infection can produce appearances that mimic malignancy.

This is one reason follow-up imaging may occasionally be recommended after treatment of pneumonia, particularly when there are clinical risk factors or persistent abnormalities.

What does lung cancer look like after contrast?

Contrast-enhanced CT helps assess:

• —the tumour
• —mediastinum
• —major blood vessels
• —lymph nodes
• —liver
• —adrenal glands
• —other relevant structures.

Current NICE guidance recommends contrast-enhanced CT of the chest for people with known or suspected lung cancer, including the lower neck, liver and adrenal glands, before biopsy where possible.^[1]

What do lymph nodes have to do with lung cancer?

Cancer can spread through lymphatic channels to lymph nodes.

For lung cancer, radiologists assess nodes including those:

• —within the hilar regions
• —around the trachea
• —within the mediastinum.

Size can raise suspicion, but:

What is PET-CT?

PET-CT combines:

• —anatomical CT imaging
• —metabolic imaging using a radioactive glucose-like tracer, usually FDG.

Many cancers demonstrate increased FDG uptake because of increased glucose metabolism.

PET-CT can help assess:

• —the primary tumour
• —lymph nodes
• —distant spread.

Why might I need a biopsy?

Imaging can estimate the likelihood that a lesion is malignant.

A biopsy obtains actual tissue.

This allows pathologists to determine:

• —whether cancer is present
• —what type of cancer it is
• —sometimes important molecular characteristics relevant to treatment.

Biopsy may be obtained through:

• —bronchoscopy
• —endobronchial ultrasound
• —CT-guided needle biopsy
• —surgery.

The safest and most informative approach depends on the location and stage of the suspected disease.

Why might doctors biopsy a lymph node instead of the lung mass?

Because the ideal investigation can sometimes provide both:

• —diagnosis and staging.

If a suspicious lymph node is accessible and proving involvement would change treatment, sampling that node may provide more useful information than simply biopsying the primary lung lesion.

NICE specifically recommends choosing investigations that provide the most information about both diagnosis and staging with the least risk.^[1]

What does “staging” mean?

Staging describes how far a cancer has spread.

Lung cancer staging considers:

• —T — Tumour: The primary tumour's size and relationship to surrounding structures.
• —N — Nodes: Whether regional lymph nodes are involved.
• —M — Metastases: Whether disease has spread to distant organs.

The current international ninth edition of TNM lung-cancer staging refines nodal and metastatic categories and is used to help guide prognosis and treatment planning.^[5]

Where can lung cancer spread?

Potential sites include:

• —lymph nodes
• —other parts of the lungs
• —pleura
• —bones
• —liver
• —adrenal glands
• —brain.

Different imaging tests may therefore be needed for complete staging.

Can CT diagnose the type of lung cancer?

Not reliably.

There are several major pathological types, including:

• —Non-small-cell lung cancer: This includes adenocarcinoma, squamous-cell carcinoma and other subtypes.
• —Small-cell lung cancer: This behaves differently and is treated differently.

Some imaging appearances are more commonly associated with particular tumour types, but CT cannot reliably replace tissue diagnosis.

Does every suspicious nodule need a biopsy?

No.

Very small nodules may be inappropriate or unsafe to biopsy.

Management may instead involve:

• —CT surveillance
• —risk modelling
• —PET-CT when appropriate
• —multidisciplinary discussion.

The decision depends on the probability of malignancy and whether obtaining tissue would alter management.

Does finding lung cancer early matter?

Yes.

Disease confined to the lung or nearby structures may be treatable with curative intent using approaches such as:

• —surgery
• —stereotactic radiotherapy
• —systemic treatment
• —combinations of therapies.

This is one reason low-dose CT screening has become increasingly important for appropriately selected higher-risk populations.

What if the report says “suspicious for primary lung malignancy”?

This means the radiologist believes the imaging features raise significant concern for a cancer arising in the lung.

It does not usually mean that CT has provided a histological diagnosis.

The next step may include:

• —respiratory or lung-cancer MDT review
• —PET-CT
• —bronchoscopy
• —biopsy
• —additional staging.

What if it says “cannot exclude malignancy”?

Radiologists use this wording when cancer remains one of the possible explanations for an abnormality.

It does not mean:

“This definitely is cancer.”

The degree of concern depends on the complete report and clinical context.

What if my CT shows a lung nodule?

Do not jump straight from:

lung nodule → lung cancer.

Most pulmonary nodules encountered in clinical practice are not automatically treated as cancers.

Their significance depends on:

• —size
• —morphology
• —growth
• —smoking history
• —age
• —previous malignancy
• —other clinical factors.

Related article: What Is a Lung Nodule?

What symptoms should be assessed?

Symptoms that deserve medical assessment include:

• —persistent cough
• —coughing up blood
• —unexplained weight loss
• —persistent breathlessness
• —recurrent chest infection
• —unexplained chest pain
• —persistent hoarseness
• —other concerning respiratory symptoms.

These symptoms have many possible causes and do not automatically mean lung cancer.

The key message

There is no single CT appearance that proves lung cancer.

Radiologists build a picture from:

• —size
• —shape
• —density
• —growth
• —lymph nodes
• —other findings
• —clinical risk.

CT is extraordinarily powerful.

But sometimes the final answer still requires tissue.