If you or someone you love has been diagnosed with mesothelioma, you probably have questions. What is the relationship between mesothelioma and lung cancer? How are they different?

These two forms of cancer are related, but they are different diseases. Although they share some symptoms, diagnostic tests, and treatments, they don’t develop in the same locations and they have varying risk factors. It’s important to understand the differences between these two conditions so you can seek out the best treatment for yourself or your loved one.

What Is Mesothelioma?

Mesothelioma is a form of cancer that occurs in the mesothelium, the lining that protects and covers all the abdominal organs and the chest cavity. While mesothelioma can develop anywhere in the mesothelium, it is most common in the lining around the lungs, known as the pleura. This form, called pleural mesothelioma, accounts for 85 percent of cases. It can also occur in the peritoneum (lining of the abdominal cavity) or the pericardium (lining around the heart).

Is Mesothelioma a Type of Lung Cancer?

Experts don’t always agree on whether mesothelioma is a form of lung cancer. What is commonly accepted is that both are types of cancer that affect the lungs.

Some cancer researchers say pleural mesothelioma is not technically lung cancer but a lung disease related to lung cancer. This is because mesothelioma occurs in the space around the lungs and not in the lungs themselves.

Other experts consider mesothelioma a type of lung cancer because there is no better way to categorize it. The disease has some symptoms similar to those of lung cancer, and lung cancer oncologists are often the doctors who treat it.

Many resources on pleural mesothelioma are vague or conflicting as to whether it’s a type of lung cancer. Ultimately, although experts may have contrasting views on the classification of mesothelioma, the important thing is to understand the specifics of the disease to get the best possible treatment for yourself or your loved one.

There are several key differences between mesothelioma and most lung cancers.

1. Mesothelioma and Lung Cancer Affect Different Tissues

As explained above, mesothelioma and lung cancer affect different structures in the body. In pleural mesothelioma, the cancer is located in the lining of the lungs. The tissue that surrounds and protects the lungs is called the pleural tissue. Mesothelioma can also affect mesothelial tissue wherever it’s located, including the heart, stomach, and testicles.

Lung cancer develops in the lung tissue. Although advanced lung cancer can spread to other areas of the body, it begins in the lungs and, when analyzed, is identifiable as a lung cancer tumor. There are several types of lung cancer, including small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC), but they all begin inside or on the lung itself.

2. Mesothelioma and Lung Cancer Have Different Risk Factors

The biggest differences between mesothelioma and lung cancer involve their causes and risk factors.

Causes of Mesothelioma

The majority of malignant (cancerous) mesothelioma cases result from exposure to asbestos, a material that was once used for insulation and fireproofing and is a known carcinogen (cancer-causing agent). Asbestos is fibrous, and asbestos fibers that are breathed in can be difficult to clear from the body. Over time, uncleared fibers can cause mesothelioma.

According to the National Organization for Rare Disorders (NORD), 70 percent to 80 percent of individuals diagnosed with mesothelioma report significant exposure to asbestos dust and products. The exposure can occur from 30 to 50 years before symptoms appear. This gives asbestos a long latency period in the body before the harm it causes can be identified. There are many other asbestos-related diseases and lung cancers, such as asbestosis, but mesothelioma is one of the best known.

Most exposure to asbestos happens on the job. People involved in occupations such as construction and roofing, as well as those doing some mechanic or production work, may have been exposed to the material.

Asbestos has been outlawed, and its use diminished drastically after 1989, according to NORD. However, people exposed to asbestos before its ban can still develop mesothelioma. Those with a history of asbestos exposure have a higher cancer risk and may choose to get tested for the condition regularly.

Causes of Lung Cancer

Smoking is the most significant cause of lung cancer, but it is not widely discussed as a cause of mesothelioma. In fact, many of those diagnosed with mesothelioma do not have a history of smoking.

Note that both mesothelioma and lung cancers can have other risk factors. Genetics seem to play a role in putting people at increased risk of developing both lung cancer and mesothelioma, as does exposure to several other carcinogenic substances such as arsenic, nickel, or radon gas.

3. Symptoms Vary Between Lung Cancer and Mesothelioma

The most notable similarity between mesothelioma and lung cancer is the overlap in symptoms, although there are some slight differences.

Symptoms of Mesothelioma

Mesothelioma in the lungs can cause people to experience:

• Significant tiredness
• A cough that’s always present and does not improve over time
• Shortness of breath that’s severe enough to interfere with daily activities
• Unexplained weight loss
• Loss of appetite
• Chest pain, often in dispersed or difficult-to-pinpoint locations
• Fever and sweating, especially at night
• Significantly swollen fingertips

Symptoms of Lung Cancer

The symptoms of lung cancer significantly overlap with those of mesothelioma, including:

• Shortness of breath
• Chest pain
• A cough — usually a new cough, although it may begin with an illness — that doesn’t resolve
• Unintentional weight loss

However, there are some differences. Lung cancer may also cause other symptoms that are not normally seen in mesothelioma, including:

• Hoarseness without another explanation
• Persistent headache
• Coughing up blood
• Pain in the bones

4. The Diagnostic Process Is Similar, but Treatment May Differ

Lung cancer diagnosis and mesothelioma diagnosis both rely on imaging tests, including X-rays and CT scans. These tests allow oncology experts and health care professionals to detect any tumors, nodules, lesions, or other indications of cancer in the lungs and their lining.

An accurate diagnosis of lung cancer and mesothelioma will also likely include some sort of biopsy (a fluid or tissue sample). This may involve collecting sputum (a mixture of mucus and saliva) or other fluid coughed up from the lungs, removing fluid from around the lungs, or taking samples of any tumors or other spots visible on the lungs. All these tests involve examining the samples for cancer cells.

Treatment

Some of the treatment options for mesothelioma and lung cancer are identical or similar. Both conditions are usually treated with a combination of surgery (to remove cancerous tissue), chemotherapy, and radiation therapy.

However, the application of these therapies may differ between conditions. Targeted lung cancer treatments are specific to the genetic mutations found in lung cancer cells, and immunotherapy may be recommended in some cases.

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Are you living with mesothelioma or lung cancer? What was your diagnostic journey like? Share your story in the comments below, or start a conversation by posting on your Activities page.