Lung Cancer Misdiagnosis: What It Is Most Commonly Confused With

A persistent cough, breathlessness, chest discomfort or recurrent chest infection can have several possible causes, many of which are much more common than cancer.

There can also be uncertainty when an abnormality appears on a scan. Infection, inflammation and scarring can sometimes resemble lung cancer, while some cancers may initially produce findings that are difficult to distinguish from other respiratory conditions.

For this reason, establishing what is causing a persistent symptom or suspicious scan usually involves several pieces of information rather than one test alone. The aim is to move from an initial concern towards a clear diagnosis that can guide the next steps.

Why Lung Cancer Can Be Difficult to Recognise

Many of the symptoms associated with lung cancer are non-specific. Coughing, wheezing, breathlessness, tiredness and chest discomfort can also occur with infections, asthma, COPD and other conditions.

The way symptoms develop over time is therefore important. A new symptom, a change in a longstanding cough, unexplained weight loss, coughing up blood or symptoms that do not improve as expected may justify further assessment.

Once cancer has been confirmed, an individualised lung cancer treatment plan depends on much more than the symptoms that first led to investigation. Doctors need to establish the cancer subtype, stage and, where appropriate, its molecular characteristics before deciding which treatments are most suitable.

Conditions That Can Resemble Lung Cancer

Several respiratory and inflammatory conditions can produce symptoms or scan findings that overlap with lung cancer.

These can include:

• Pneumonia and other chest infections
• Chronic obstructive pulmonary disease (COPD)
• Asthma
• Tuberculosis
• Sarcoidosis and other inflammatory conditions
• Previous lung scarring
• Benign pulmonary nodules

These conditions can overlap with some of the signs and symptoms of lung cancer, which may include a persistent cough, breathlessness, chest pain, unexplained weight loss and recurrent chest infections. This overlap is one reason symptoms alone cannot establish what is causing them.

Having one of these conditions does not rule lung cancer in or out. Equally, an abnormal scan does not automatically mean that cancer is present. The distinction becomes clearer by looking at how symptoms behave, reviewing imaging carefully and using tissue sampling where needed.

Persistent or Recurrent Chest Infections

Pneumonia can cause coughing, breathlessness, chest discomfort, tiredness and abnormalities on a chest X-ray. In many cases, these findings resolve with appropriate treatment.

Further investigation may be needed when symptoms persist, an imaging abnormality does not improve as expected, or infections repeatedly affect the same area of the lung.

A tumour can sometimes narrow or obstruct an airway, which may contribute to infection beyond the obstruction. Recurrent infection in one area can therefore prompt doctors to investigate whether there is an underlying cause. Changes in mucus or coughing up white phlegm can also have several possible explanations, including infection, irritation or changes affecting the airways.

This does not mean that persistent pneumonia is usually cancer. It means that symptoms or imaging findings that do not follow the expected pattern may need to be reassessed.

COPD, Asthma and Changes in Respiratory Symptoms

COPD and asthma can both cause coughing, breathlessness and wheezing. These symptoms can overlap with lung cancer, particularly during the earlier stages when cancer-related symptoms may be relatively non-specific.

For someone already living with COPD or asthma, an important clue can be a change from their usual pattern. A cough that becomes different, unexplained weight loss, coughing up blood or symptoms that are no longer responding as expected should not simply be assumed to come from an existing respiratory condition.

Lung function testing can help assess conditions such as COPD, but it cannot show whether a tumour is present. This is why a pulmonary function test cannot detect lung cancer. Imaging and, where necessary, tissue sampling provide different information.

Infection, Inflammation and Suspicious Scan Findings

Some infections and inflammatory diseases can closely resemble cancer on imaging.

Tuberculosis may cause persistent coughing, weight loss, lung abnormalities and enlarged lymph nodes. Sarcoidosis can also affect the lungs and lymph nodes in ways that may initially raise concern about malignancy.

Even PET-CT cannot always distinguish these conditions with certainty. Increased metabolic activity is seen in many cancers, but infection and inflammation can also produce increased uptake.

This is one reason a PET-positive area does not automatically establish a cancer diagnosis. If the distinction would affect treatment, additional imaging or tissue sampling may be needed.

Lung Nodules and Areas of Scarring

Not every lung nodule is cancerous.

Nodules can develop for several reasons, including previous infection, inflammation and other benign processes. Areas of lung scarring may also produce appearances on imaging that require closer assessment.

Doctors consider features such as a nodule's size, shape, location and whether it changes over time. Comparing a current scan with previous imaging can be particularly useful because long-term stability may provide reassuring information.

However, a new, enlarging or otherwise suspicious lesion may require further investigation before its significance can be determined.

Building a Clearer Diagnosis

No single investigation answers every question about suspected lung cancer.

A chest X-ray may reveal the first abnormality, while CT provides more detailed information about its location and appearance. PET-CT may contribute information about metabolic activity and whether there are suspicious areas elsewhere in the body.

When tissue confirmation is required, a biopsy may be obtained through bronchoscopy, endobronchial ultrasound, CT-guided biopsy or another technique depending on where the abnormality is located.

Pathology can then establish whether cancer cells are present and what type of lung cancer has developed. In non-small cell lung cancer, additional molecular testing may identify features that influence treatment.

When the First Investigation Is Inconclusive

Sometimes the first round of testing does not provide a definite answer.

A biopsy may contain too little tissue for a reliable diagnosis, an abnormality may be difficult to reach safely, or imaging may remain uncertain when infection or inflammation is still a realistic possibility.

The next step depends on the degree of concern and the individual circumstances. This may involve repeat imaging, another form of biopsy or a different investigation.

An inconclusive result does not necessarily mean that something has gone wrong. Some abnormalities simply require more than one investigation before their significance becomes clear.

When Lung Cancer Is Confirmed After Another Diagnosis

Being diagnosed with lung cancer after symptoms were initially attributed to another condition can understandably raise questions about whether the cancer should have been recognised earlier and why the diagnosis now needs to be approached with appropriate urgency.

There is not always a straightforward answer.

Many lung cancer symptoms overlap with common respiratory illnesses, and an initial diagnosis such as a chest infection may have been reasonable based on the information available at the time. Some cancers also produce few or non-specific symptoms during their earlier stages.

What matters clinically is appropriate reassessment when symptoms persist, worsen or behave differently from what was expected.

Once lung cancer is confirmed, attention turns to establishing its subtype, stage and relevant molecular characteristics so that treatment can be planned accurately. At this stage, discussing the findings with a private oncology consultant can help provide greater clarity around the treatment options available and how they relate to the individual diagnosis.

Specialist Review When Questions Remain

Even after a diagnosis has been established, there can still be uncertainty about staging, pathology or the most appropriate treatment approach.

This may be particularly relevant when different investigations appear inconsistent, the pathology is unusual, or more than one reasonable treatment option has been proposed.

A second opinion can also provide an independent review when you want greater clarity about an established diagnosis or proposed treatment plan. This can help explain why a particular approach has been recommended and whether other reasonable options should be considered.

About Dr James Wilson

Lung cancer can sometimes resemble other respiratory conditions, while non-cancerous conditions can also produce suspicious findings on imaging. Reaching a clear diagnosis may therefore require information from several investigations.

Dr James Wilson is a consultant clinical oncologist in full-time private practice in Central London, specialising in lung cancer and advanced radiotherapy. He supports patients with established cancer diagnoses who want greater clarity around their results, treatment recommendations and available oncology options.