Lung Cancer vs. Pneumonia: What Are the Differences?

It can be difficult to tell if you have pneumonia or lung cancer because they share similar symptoms. However, there are fundamental differences between the two.

To start, pneumonia is a chest infection that causes inflammation of the air sacs in the lungs. Lung cancer, on the other hand, occurs when cells grow out of control and form tumors.

Signs of lung cancer are hard to detect until it has reached a late stage, while pneumonia symptoms come on within a few days of contracting the infection. Symptoms common to both conditions include chest pain, a persistent cough, and fatigue.

This article takes you through the symptoms, causes, diagnosis, and treatment of each condition.

This article will discuss the similarities and differences between pneumonia and lung cancer.

Symptoms

Pneumonia and lung cancer share overlapping symptoms, including:

• A new cough that doesn’t go away
• An increase in phlegm that could be green, yellow, rust-colored, or bloody
• Shortness of breath
• Chest pain that gets worse when you cough, breathe, or laugh
• Loss of appetite
• Low energy and fatigue

The main difference between these overlapping symptoms is their onset and progression. Lung cancer symptoms take a while to develop, which is why most lung cancer cases aren’t diagnosed until it has already spread to other parts of the body. Pneumonia, on the other hand, causes severe symptoms shortly after the infection begins.

Also, the two conditions have some distinct symptoms.

Causes

Although having pneumonia can increase the risk of developing lung cancer in some people, the two conditions are caused by different things.

Lung Cancer Causes

As many as 90% of all lung cancer cases are caused by smoking. The remaining 10% are caused by various factors such as:

• Exposure to radon gas, asbestos, secondhand smoke, or air pollution 
• A history of chronic infections

In rare cases, researchers believe that lung cancer could be tied to inherited genetic mutations or passed down through families.

Pneumonia Causes

Pneumonia is caused by bacteria, viruses, and fungi. The most common form of pneumonia, bacterial pneumonia, is typically caused by Streptococcus pneumoniae. However, it can also be caused by other types of bacteria, such as Mycoplasma pneumoniae, Chlamydophila pneumoniae, or Legionella pneumophila.

Viral pneumonia, the type that is caused by a virus, is the result of the common influenza virus in adults. In children, the virus that commonly causes viral pneumonia is the respiratory syncytial virus.

Fungal pneumonia isn’t as common. The types of fungi that can cause pneumonia include Coccidioidomycosis, Histoplasmosis, and Cryptococcus.

Pneumonia in Lung Cancer Patients 

Pneumonia in lung cancer is incredibly common. Research has found that of all patients battling lung cancer, as many as 70% will also have pneumonia.

Bacterial pneumonia is associated with a higher risk of lung cancer. Research found that people who have had pneumonia before were over three times as likely to develop lung cancer compared to people who never had pneumonia.

Research has also shown that when people have both diseases at the same time, their likelihood of survival decreases significantly. This can lead to complications, such as:

• Lung abscess: A lung abscess occurs when dead lung tissue turns into a liquid, mainly pus. 
• Empyema: Empyema occurs when pockets of pus start to collect in the space between the lungs and the chest cavity, otherwise known as the pleural cavity.
• Fistula formation: A fistula is a hole or opening that can form between the bronchi—the large airways within the lungs—and the pleural cavity.

Pneumonia is a leading cause of death in lung cancer patients.

Diagnosis

Diagnosing lung cancer and pneumonia requires different processes, even though the two often share similar symptoms.

Pneumonia Diagnosis

Diagnosing pneumonia typically involves a physical exam to assess abnormal breathing, fever, and swollen glands. A sample of phlegm will be taken and tested to help figure out the source of the infection.

A chest X-ray will likely be performed as well. Chest X-rays take pictures of the lungs, which help determine if there is an abnormal buildup of fluid or pus in the lungs.

A blood test will also be done to help identify whether your pneumonia is caused by bacteria, viruses, or fungi. Knowing this can help your healthcare provider determine the best treatment.

Lung Cancer Diagnosis

To diagnose lung cancer, your healthcare provider will perform a physical exam and order a chest X-ray to look at your lungs. On a chest X-ray, any abnormal growth will appear as a relatively solid area of light gray, which could be cancer or many noncancerous conditions. A chest X-ray alone cannot confirm cancer.

For this reason, a computerized tomography (CT) scan will also be ordered if cancer is suspected. This type of scan can better visualize tumors, their size and shape, and their location in the lungs.

A spot on the lung (or a lung nodule) may be found after a chest X-ray or CT scan. Most lung nodules seen on X-rays or CT scans are not cancer. Although tests are often needed to confirm a nodule is noncancerous, they often stem from other causes such as:

• Enlarged lymph nodes
• Infections (e.g., pneumonia, tuberculosis)
• Fungal lung diseases
• Impacted phlegm
• Scar tissue
• Cysts

A biopsy—which is a procedure where a piece of tissue where cancer is suspected is removed and tested—is used to confirm that cancer cells are present in the tumors.

Currently, a low-dose CT (LDCT) scan can be used to regularly screen those at increased risk for lung cancer (e.g., smokers or former smokers). Research shows that yearly LDCT scans of high-risk individuals can detect lung cancer early (before symptoms start) and save lives.

Lung Cancer Healthcare Provider Discussion Guide

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To see whether the cancer has spread, your healthcare provider will order an MRI of the brain and a PET scan, which is similar to a CT scan but offers a more detailed picture of the lungs and other areas of the body where cancer may have spread.

Treatment

Getting a proper diagnosis for pneumonia or lung cancer is crucial because the treatments for the two conditions are very different.

Lung Cancer Treatment

Various factors need to be taken into account when determining a treatment plan, such as the type of lung cancer you have, whether it has spread, and your overall health. According to the Centers for Disease Control and Prevention, there are four main treatment options for lung cancer:

• Surgery: If cancer in the lungs is contained, surgery may be an option. During surgery, the cancerous tissue is cut out of the body.
• Chemotherapy: Chemotherapy refers to the medications designed to kill cancer cells. This type of treatment is often used in combination with other therapies to improve the patient’s chances of survival in cases where cancer has spread to other areas of the body.
• Radiation therapy: Radiation therapy uses radiation to kill or control the growth of cancer cells. The specific types of radiation, or energy, used in cancer treatments are X-rays, gamma rays, electron beams, and protons. High doses are targeted at cancer cells, which causes chemical changes in the cells and leads to DNA damage. This prevents cancer cells from replicating.
• Targeted therapy: Targeted therapy uses medications to stop a cancer cell from making copies of itself. Although it is similar to chemotherapy, targeted therapy drugs act only on specific cancer cells, as opposed to all cells that are dividing rapidly. 
• Immunotherapy: This works by using medications to trigger the immune system to help get rid of cancer cells.

Pneumonia Treatment

Treatment for pneumonia depends on how serious the condition is. In some cases, pneumonia will clear up on its own. Some home remedies for mild cases include:

• Controlling fever and inflammation with over-the-counter medications
• Drinking a lot of fluids and warm beverages
• Taking baths or using a humidifier to open your airways
• Getting a lot of rest

A case of bacterial pneumonia will be treated using an antibiotic, such as azithromycin. In people with other chronic conditions such as heart disease and diabetes, other antibiotics such as fluoroquinolone may be used because there is a chance that the bacteria causing their pneumonia may be resistant to other types of antibiotics.

Research has shown that corticosteroids, which are drugs designed to reduce inflammation, can also be used to treat pneumonia. They help decrease the risk of death and the need for more serious medical interventions, such as a ventilator or prolonged hospitalization in people who have more serious cases of infection.

If you are hospitalized, you will be given medications through an IV directly into your bloodstream. You may also need help breathing, so oxygen therapy will be used. You could be given oxygen through a face mask, your nose, or another piece of medical equipment such as a ventilator.

Summary

Although lung cancer and pneumonia have different causes they can show some similar signs and symptoms. Early diagnosis is key, and lung cancer and pneumonia also have some tests in common during the diagnostic process. Treatments vary widely for each but both conditions can be managed and lung cancer outcomes are greatly improved with early detection.