Mesothelioma and Lung Cancer

Mesothelioma and lung cancer are not the same types of cancer. They are diagnosed and treated very differently, but because mesothelioma is rare, it is often misdiagnosed as lung cancer. Getting a thorough diagnosis for symptoms, including second or third opinions, is essential.

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Mesothelioma and Lung Cancer

Mesothelioma and lung cancer are not the same types of cancers, although they have similarities. Contrary to what many people think, mesothelioma is not a type of lung cancer.

What Is Mesothelioma?

Mesothelioma is a type of cancer that grows in the mesothelium, a double layer of tissue surrounding organs in the body. It is most often caused by asbestos exposure.

The most common form of mesothelioma affects the pleural tissue around the lungs. Pleural mesothelioma has several similarities to lung cancer and is often misdiagnosed as lung cancer. Less common is peritoneal mesothelioma, which develops in the abdomen.

Pleural mesothelioma causes symptoms that include chest pains, shortness of breath, and a persistent cough.

What Is Lung Cancer?

Lung cancer is an abnormal growth of cells (cancer cells) in one or both lungs. Lymph nodes may or may not be involved. When abnormal cells begin to divide and grow rapidly, they can cause a variety of symptoms.

Common symptoms of lung cancer include:

• Shortness of breath
• Cough
• Decreased oxygenation
• Chest discomfort

The primary cause of lung cancer is smoking.

Types of Lung Cancer

Lung cancer occurs as one of two main types: small cell and non-small cell. Almost 85% of all lung cancer cases are non-small cell lung cancer.[1] Most other cases are classified as small cell lung cancer.

Adenocarcinoma

Adenocarcinoma is non-small cell and the type of lung cancer most commonly associated with non-smokers. Although smoking is the leading cause of adenocarcinoma and other lung cancers, it is not the only cause.[1] Mesothelioma is often misdiagnosed as adenocarcinoma.

Squamous Cell Carcinoma

This type of non-small cell lung cancer develops in cells on the interior lining of the airways, often in the bronchus. It is most common in smokers.

Large Cell Carcinoma

Characterized by larger cells and rapid spread, large cell carcinoma can begin in any area of the lung. It is difficult to treat.

Small Cell Lung Cancers

Though less common, small cell lung cancer is much more aggressive. It grows and spreads rapidly and should be treated immediately.

Small cell lung cancer is not staged in the same way as non-small cell lung cancer. Its two categories are limited stage or extensive stage.[1]

Lung Carcinoid

Lung carcinoid is now more commonly diagnosed than in the past. Carcinoid is very different from non-small cell and small cell lung cancers. This tumor starts with different types of cells called neuroendocrine cells (cells that produce hormones).

These cells line the small intestines as well as the lungs and can be typical or atypical. Many cancer centers have developed carcinoid programs to treat patients with this specific malignancy.[1]

How Is Mesothelioma Different From Lung Cancer?

Malignant mesothelioma is not the same as lung cancer. This cancer affects the lining of organs, including not only the lungs but also the abdomen and heart.

There are three main types of mesothelioma. The most common type is epithelioid. Other types are sarcomatoid and mixed/biphasic. Epithelioid mesothelioma grows slowly and often responds better to treatment than the other types.

Several factors make mesothelioma stand out from lung cancer:

• Mesothelioma is not directly linked with smoking. Although cigarette smoking can worsen mesothelioma symptoms, it is not the direct cause of the disease. Smoking is the primary cause of lung cancer.
• Mesothelioma’s primary cause is asbestos exposure. The exposure to asbestos may be direct (working in a shipyard or installing asbestos driveways) or indirect (washing the clothes of a spouse who worked in a plant or shipyard). Exposure may occur via inhalation (breathing in asbestos) or ingestion (swallowing asbestos fibers). Victims typically do not realize they are being exposed.
• Mesothelioma grows diffusely throughout the mesothelium, rather than as distinct large masses. It can be found in the lining of the lung (pleura), the lining of the heart (pericardium), or the lining of the abdomen (peritoneum).
• Mesothelioma grows aggressively and rapidly. It metastasizes quickly, which makes it difficult to treat. By the time mesothelioma is diagnosed, it is often impossible to use surgery or achieve remission.

Diagnosing Mesothelioma and Lung Cancer

Because mesothelioma and lung cancer both manifest in the same area of the body and cause similar symptoms, it can be difficult to make an accurate diagnosis. These are some of the diagnostic differences between lung cancer and mesothelioma:

• In imaging scans, mesothelioma shows pleural thickening and multiple nodules with poorly-defined boundaries. Lung cancer is more likely to show well-defined masses.
• Biopsy samples help pathologists identify the cells in which the cancer originated. Lung cells and mesothelial cells have some different characteristics.
• Biomarkers in the blood can also be used to distinguish between the two types of cancer. Some markers are more prevalent in people with mesothelioma.

Treating Mesothelioma and Lung Cancer

Mesothelioma is most often treated with chemotherapy rather than surgery. Because it forms so many small nodules and spreads rapidly, surgeons cannot remove all the cancer. Systemic chemotherapy is a better approach.

Lung cancer treatment depends on the stage and type. Surgery can remove most of the tumors if the cancer has not spread very far.

Oncologists usually approach mesothelioma and lung cancer with multimodal treatment. This means they use more than one strategy, such as surgery followed by chemotherapy.

Can Mesothelioma Cause Lung Cancer?

Mesothelioma does not cause lung cancer. However, they can be caused by the same thing: asbestos. Past exposure to asbestos is the leading cause of mesothelioma.

Smoking is the leading cause of lung cancer, but asbestos can also cause it. Someone exposed to asbestos might develop either type of cancer.

The Prognosis for Lung Cancer and Mesothelioma

The prognosis for mesothelioma is almost always poor. The prognosis for lung cancer is more variable. It depends on the type of lung cancer and how far it has spread.

One measure of prognosis is the five-year survival rate. This is the percentage of patients still alive five years after their diagnosis. These are the mesothelioma and lung cancer five-year survival rates according to the American Cancer Society:[2][3]

• Mesothelioma – 12%
• Non-small cell lung cancer – 26%
• Small cell lung cancer – 7%

Prognosis varies by type and by disease stage. For instance, patients diagnosed with early non-small cell lung cancer have a five-year survival rate of 64%. For patients with early-stage mesothelioma, it is only 20%.

Asbestos-Related Lung Disease

While mesothelioma and lung cancer are two separate diseases, it is still possible to develop lung cancer after asbestos exposure.[4] Many studies show an increased risk of lung cancer in workers exposed to asbestos. Those who have been exposed to asbestos and also smoke have a higher chance of lung cancer.

Asbestosis is another condition directly related to asbestos exposure. Over time, the lung tissue becomes scarred and can become lung cancer, and smoking compounds the risk of asbestosis becoming lung cancer.

Although both diseases have very similar symptoms, they are very different cancers in how they are diagnosed and treated.

Page Medically Reviewed and Edited by Pinar Kanlikilicer, PhD

Dr. Pinar Kanlikilicer has a PhD in Biomedical Engineering. She completed her 5-years of postdoctoral training in the Department of Experimental Therapeutics at MD Anderson Cancer Center. She is currently working in the field of cancer as a research scientist.

Learn more about Cancer Research Specialist Pinar Kanlikilicer, PhD