Lung Cancer vs. Pneumonia: What Are the Differences?

Lung Cancer vs. Pneumonia Symptoms and Signs

Picture of lung cancer
Picture of lung cancer
  • Lung cancer is a general term that includes all abnormal lung tissue cells that multiply unregulated and form tumors or growths in the lungs. These tumor cells may spread (metastasize) to other parts of the body.
  • Pneumonia is an infection of lung tissue usually caused by viruses, bacteria, fungi, and/or parasites. However, bacteria and viruses cause the majority of pneumonia infections.
  • Lung cancer and pneumonia both cause the same symptoms and signs that may include:
  • Other similar signs and symptoms of lung cancer and pneumonia include:
  • Signs and symptoms of lung cancer that do not occur with pneumonia infections may include:
  • Signs and symptoms of pneumonia that do not occur in lung cancer include:
    • Fever
    • Shaking
    • Chills
    • Large amounts of sputum production
  • People who have recurrent bouts of pneumonia may have an unidentified lung cancer.
  • The main cause of lung cancer is tobacco use (about 90%) due to the cancer-causing chemicals in inhaled tobacco smoke. About 10% of lung cancers are caused by or related to:
  • Pneumonia is caused by many viruses, bacteria, fungi, and parasites, for example, Streptococcus pneumoniae, which is the most common bacterial cause lung infections.
  • If a person with lung cancer gets pneumonia, he or she is at increased risk for a poor prognosis and life expectancy because the mass of lung cancer cells (tumors) take oxygen and nutrients away from normal cells. The cancerous tumor(s) cause a decrease in normal lung cell functioning, which can block the airways of the lungs leading conditions susceptible to infections. Moreover, a lung infection further compromises the ability of the lungs to function properly.
  • If a person with metastatic lung cancer develops pneumonia, the survival rate is less than 5% over 5 years, in contrast the survival rate of people with pneumonia who do not have lung cancer (about 95%).

What Is Lung Cancer? What Is Pneumonia?

Lung Cancer

  • Lung cancer is a group of diseases characterized by abnormal growths (cancers) that started in the lungs.
  • Lung cancer is the leading cause of cancer deaths in women and men both in the United States and throughout the world. Lung cancer has surpassed breast cancer as the leading cause of cancer deaths in women for the past 25 years. In the United States, there are more deaths due to lung cancer than the number of deaths from colon and rectal, breast, and prostate cancer combined.
  • At least half of the people with lung cancer will survive and be free of recurrent cancer five years later if it is diagnosed at an early stage. Once lung cancer has spread to other distant organs (metastasized), the five-year overall survival is less than 5%.
  • Cancers are also called malignant (cancerous) tumors, and most lung tumors are cancerous. Metastasis occurs when these cancerous tumors spread to nearby lymph nodes or through the bloodstream to other organs.
  • Lung cancer comprises a group of different types of tumors. About 95% of all cases of lung cancers are divided into two main groups, small cell lung cancers (SCLCs) and non-small cell lung cancer (NSCLC). The division into groups is based on the type of cells that make up the cancer. Cell size and type of tumor when viewed under a microscope characterizes the two main types of cancer.
  • Small cell lung cancers (SCLCs) are less common and grow more quickly. Moreover, they are more likely to have spread to other parts of the body by the time the cancer is diagnosed than are non-small cell lung cancers (NSCLCs).
  • Non-small cell lung cancer (NSCLC) includes several subtypes of tumors.
  • About 5% of lung cancers are of rare cell types, including carcinoid tumor, lymphoma, and others.
  • Subtypes of primary lung cancers include:
    • Adenocarcinoma (an NSCLC), the most common type of lung cancer, which occurs in about 30% to 40% of all cases.
    • A subtype of adenocarcinoma is called bronchoalveolar cell carcinoma creates a pneumonia-like appearance on chest X-rays.
    • Squamous cell carcinoma (an NSCLC) is the second most common type of lung cancer and is responsible for about 30% of all cases.
    • Large cell cancer (another NSCLC) is responsible for about 10% of all cases.
    • Small cell lung cancer is responsible for about 20% of all cases.
    • Carcinoid tumors are responsible for 1% of all cases.


Picture of pneumonia infection
Picture of pneumonia infection

Pneumonia is an infection of one or both lungs usually is caused by bacteria, viruses, fungi, or parasites. There are many types of pneumonia based on the type of microbe causing the infection. Moreover, a microbe can cause different kinds of pneumonia. Sometimes pneumonia affects a portion of one lung, and in other cases, the infection has throughout both lungs. Some people with pneumonia develop associated fluid collections. Some causes of pneumonia can be very destructive to lung tissue, for example, Staphylococcus aureus.

One-third of all people who developed pneumonia subsequently died from the infection before antibiotics were discovered. Currently, over 3 million people develop pneumonia each year in the United States. Over a half a million of these people are hospitalized for treatment. Although most of these people recover, approximately 5% will not recover from the infection and die. Pneumonia is the sixth leading cause of death in the United States.


Lung cancer is a disease in which lung cells grow abnormally in an uncontrolled way. See Answer

What Are the Differences in the Signs and Symptoms of Lung Cancer and Pneumonia?

Lung Cancer Symptoms and Signs

Up to one-fourth of all people with lung cancer may have no symptoms by the time cancer is diagnosed. These cancers usually are diagnosed incidentally when a chest X-ray is performed for another reason. However, most people develop symptoms of lung cancer before being diagnosed. Lung cancer symptoms are due to direct effects of the primary tumor. However, if the cancer has spread to other parts of the body, it may cause problems with the body’s hormones, blood, and function of other organs.

Symptoms of primary lung cancers include:

  • Coughing up blood (hemoptysis) , which occurs in a significant number of people who have lung cancer. Any amount of coughed-up blood is cause for concern. If you have a cough that does not go away or gets worse, call a doctor for an evaluation.
  • Chest pain that is dull, aching, and persistent occur in about one-fourth of people with lung cancer.
  • Shortness of breath usually results from an airflow blockage in part of the lung, collection of fluid around the lung (pleural effusion), or the spread of tumor throughout the lungs.

Other signs and symptoms of lung cancer include:

  • Wheezing or hoarseness, which cause blockage or inflammation in the lungs.
  • Repeated respiratory infections, such as bronchitis or pneumonia.

Symptoms of lung tumors that have spread to other areas of the body depends upon their location and size. About 30% to 40% of people with lung cancer have some symptoms or signs of cancer that has spread.

Lung cancer most often spreads to the liver, the adrenal glands, the bones, and the brain.

  • Metastatic lung cancer in the liver may cause a loss of appetite, feeling full early on while eating, and otherwise unexplained weight loss.
  • Metastatic lung cancer in the adrenal glands also typically causes no symptoms.
  • Metastasis to the bones is most common with small cell cancers but also occurs with other lung cancer types. Lung cancer that has metastasized to the bone causes bone pain, usually in the backbone (vertebrae), the large bones of the thigh (the femurs), the pelvic bones, and the ribs.
  • Lung cancer that spreads to the brain can cause difficulties with vision, weakness on one side of the body, and/or seizures.

Paraneoplastic syndromes are the remote, indirect effects of cancer not related to direct invasion of an organ by tumor cells. Often chemicals released from the cancers cause them. Symptoms of paraneoplastic syndromes include:

  • Clubbing of fingers -- the depositing of extra tissue under the fingernails
  • New bone formation -- along the lower legs or arms
  • Increased risk of blood clots in the arms, legs, or lungs
  • Low sodium levels
  • High calcium levels
  • Low potassium levels
  • Degenerative conditions of the nervous system otherwise unexplained.

Pneumonia Symptoms and Signs

Most people who develop pneumonia initially have symptoms of a cold (upper respiratory infection, for example, sneezing, sore throat, cough), which are then followed by a high fever (sometimes as high as 104 F), shaking chills, and a cough with sputum production. The sputum is usually discolored and sometimes bloody. Depending on the location of the infection, certain symptoms are more likely to develop.

When the infection settles in the air passages, cough and sputum tend to predominate the symptoms. In some, the spongy tissue of the lungs that contain the air sacs is more involved. In this case, oxygenation of the blood can be impaired, along with stiffening of the lung, which results in shortness of breath. At times, the individual's skin color may change and become dusky or purplish (a condition known as cyanosis) due to their blood being poorly oxygenated.

The only pain fibers in the lung are on the surface of the lung, in the area known as the pleura. Chest pain may develop if the outer aspects of the lung close to the pleura are involved in the infection. This pain usually is sharp, and worsens when taking a deep breath. This pain is called pleuritic pain or pleurisy.

Depending upon the cause of the infection, the only symptoms of pneumonia may be cough that worsens, headaches, and muscle aches that develop slowly.

Children and babies who develop pneumonia often do not have any specific signs of a chest infection, but develop a fever, appear quite ill, and can become lethargy. Elderly people also may have few of the characteristic symptoms with pneumonia.

What Causes Lung Cancer? Can Secondhand Smoke Cause Lung Cancer?

The greatest cause of lung cancer is cigarette smoking. Research as far back as the 1950s clearly established this relationship.

  • Cigarette smoke contains more than 4,000 chemicals, many of which have been identified as causing cancer.
  • A person who smokes more than one pack of cigarettes per day has a 20-25 times greater risk of developing lung cancer than someone who has never smoked.
  • Once a person quits smoking, his or her risk for lung cancer gradually decreases. About 15 years after quitting, the risk for lung cancer decreases to the level of someone who never smoked.
  • Cigar and pipe smoking increases the risk of lung cancer but not as much as smoking cigarettes.

About 90% of lung cancers arise due to tobacco use. The risk of developing lung cancer is related to the following factors:

  • The number of cigarettes smoked
  • The age at which a person started smoking
  • How long a person has smoked (or had smoked before quitting)

Risks of getting lung cancer include:

  • Passive smoking, or secondhand smoke, is a risk for getting lung cancer. An estimated 3,000 lung cancer deaths occur each year in the U.S. that are attributable to passive smoking.
  • Air pollution from motor vehicles, factories, and other sources probably increase the risk for lung cancer, and many experts believe that prolonged exposure to polluted air is similar to prolonged exposure to passive smoking in terms of risk for developing lung cancer.
  • Asbestos exposure increases the risk of lung cancer nine times. A combination of asbestos exposure and cigarette smoking raises the risk to as much as 50 times. Another cancer known as mesothelioma (a type of cancer of the inner lining of the chest cavity and the outer lining of the lung called the pleura, or of the lining of the abdominal cavity called the peritoneum) is also strongly associated with exposure to asbestos.
  • Other lung diseases, such as tuberculosis (TB) and chronic obstructive pulmonary disease (COPD), also create a risk for lung cancer. A person with COPD has a four to six time’s greater risk of lung cancer even when the effect of cigarette smoking is excluded.
  • A person who has had lung cancer is more likely to develop a second lung cancer than the average person is to develop a first lung cancer.

Exposure to Radon and Other Toxins

Radon is a byproduct of naturally occurring radium, which is a product of uranium. Radon is present in indoor and outdoor air. The risk for lung cancer increases with significant long-term exposure to radon, although no one knows the exact risk. An estimated 12% of lung cancer deaths are attributable to radon gas, or about 21,000 lung cancer-related deaths annually in the U.S. Radon gas is the second leading cause of lung cancer in the United States after cigarette smoking. As with asbestos exposure, smoking greatly increases the risk of lung cancer with radon exposure.

Certain occupations where exposure to arsenic, chromium, nickel, aromatic hydrocarbons, and ethers occurs may increase the risk of lung cancer.

What Are Common Causes Pneumonia? Are the Signs and Symptoms the Same?

Bacterial, Viral, and Fungal Causes of Pneumonia and Associated Symptoms

  • Streptococcus pneumoniae is the most common cause of a bacterial pneumonia. In this form of pneumonia, there usually is an abrupt onset of the illness with symptoms shaking chills, fever, and production of a rust-colored sputum. The infection spreads into the blood in 20%-30% of cases (known as sepsis), and if this occurs, 20%-30% of these patients die.
  • Klebsiella pneumoniae and Hemophilus influenzae are bacteria that often cause pneumonia in people suffering from chronic obstructive pulmonary disease (COPD) or alcoholism.
  • Mycoplasma pneumoniae is a type of bacteria that often causes a slowly developing infection. Symptoms include fever, chills, muscle aches, diarrhea, and rash. This bacterium is the principal cause of many pneumonias in the summer and fall months, and the condition often referred to as "atypical pneumonia."
  • Legionnaire's disease is caused by the bacterium Legionella pneumoniae that is most often found in contaminated water supplies and air conditioners. It is a potentially fatal infection if not accurately diagnosed. Pneumonia is part of the overall infection, and symptoms include high fever, a relatively slow heart rate, diarrhea, nausea, vomiting, and chest pain. Older men, smokers, and people whose immune systems are suppressed are at higher risk of developing Legionnaire's disease.
  • Mycoplasma, Legionnaire's, and another infection, Chlamydia pneumoniae, all cause a syndrome known as atypical pneumonia, or "walking pneumonia" (a term that is rarely used today). In this syndrome, the chest X-Ray shows diffuse abnormalities, yet the patient does not appear severely ill. These infections are very difficult to distinguish clinically and often require laboratory evidence for confirmation.
  • Pneumocystis jiroveci (formerly known as Pneumocystis carinii) pneumonia is another form of pneumonia that usually involves both lungs. It is seen in patients with a compromised immune system, either from chemotherapy for cancer, HIV/AIDS, and those treated with TNF (tumor necrosis factor), such as for rheumatoid arthritis.
  • Viral pneumonias can be caused by adenovirus, rhinovirus, influenza virus (flu), respiratory syncytial virus (RSV), and parainfluenza virus, which also causes croup).
  • In the US, rarely, fungal infections are responsible for may cause pneumonia, for example, histoplasmosis, coccidiomycosis, blastomycosis, aspergillosis, and cryptococcosis.

When Should I Call the Doctor If I Have Signs and Symptoms of Lung Cancer?

See a doctor as soon as possible if any of the following symptoms develop.

  • Any symptom of lung cancer
  • New cough or change in an existing cough
  • Hemoptysis (flecks of blood in the sputum when coughing)
  • Unexplained weight loss
  • Unexplained persistent fatigue
  • Unexplained deep aches or pains

Call 911 or go immediately to the nearest hospital emergency department if you have any of these symptoms.

  • Coughing up a large amount of blood
  • Sudden shortness of breath
  • Sudden weakness
  • Sudden vision problems
  • Persistent chest pain

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Common Symptom of Pneumonia & Lung Cancer


  • A cough is an action the body takes to get rid of substances that are irritating to the air passages, which carry the air a person breathes in from the nose and mouth to the lungs.
  • A cough occurs when cells along the air passages get irritated and trigger a chain of events.
  • The result is air in the lungs is forced out under high pressure.
  • A person can choose to cough (a voluntary process), or the body may cough on its own (an involuntary process).
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