Why Mesothelioma Is Often Misdiagnosed, Finding the Right Specialist and How to Avoid Being Misdiagnosed

Mesothelioma is a very rare and complex form of cancer, with approximately 3,000 cases diagnosed annually in the U.S. In addition to the low prevalence of mesothelioma, the symptoms associated with this malignant disease can easily be mistaken for the signs of less severe respiratory or gastrointestinal conditions such as asthma, pneumonia or irritable bowel syndrome. Occasionally, mesothelioma can also be misdiagnosed as lung cancer or adenocarcinoma, a form of cancer that affects the mucus-secreting glands. Receiving a reliable and accurate diagnosis is crucial, as mesothelioma has very aggressive progress and treatment should never be unnecessarily delayed.

Mesothelioma Is Frequently Misdiagnosed As Other Lung Conditions

The symptoms of mesothelioma are often confused with various other common lung diseases, which could be benign or serious.

Pleural mesothelioma: This type of mesothelioma accounts for nearly 80% of all diagnosed mesothelioma cases. The most commonly experienced symptoms of pleural mesothelioma, include shortness of breath, chest pain, fatigue, a persistent cough, and unintentional weight loss. However, these signs are frequently associated with the following lung conditions and because of this pleural mesothelioma is often misdiagnosed as either of these listed conditions:

• asthma
• tuberculosis
• pneumonitis
• emphysema
• lung cancer
• synovial sarcomatoid carcinoma
• adenocarcinoma
• mesothelial hyperplasia
• malignant neoplasm
• pulmonary fibrosis
• chronic obstructive pulmonary disease

Peritoneal mesothelioma represents less than 20% of all cases and typically entails symptoms such as abdominal pain, fatigue, unexplained weight loss, excess fluid in the abdomen, loss of appetite, and build-up of gas. Similar signs also accompany less severe gastrointestinal conditions like irritable bowel syndrome, as well as other malignant diseases occurring in the abdominal cavity. Hence, peritoneal mesothelioma may be misdiagnosed as any of these conditions:

• colorectal adenocarcinoma
• primary peritoneal carcinoma
• stomach cancer

Approximately 2% of all mesothelial tumors develop on the outer lining of the heart, hence the extremely low number of pericardial mesothelioma patients. The most frequently experienced symptoms are heart palpitations, difficulty breathing, fatigue, fever, night sweats, chest pain and persistent coughing, which can also be found in patients suffering from:

• pericarditis
• heart murmur
• pleural effusion

As a result, pericardial mesothelioma is often mistaken as pericarditis, heart murmur or pleural effusion.

Testicular mesothelioma is the rarest form, occurring in less than 1% of patients diagnosed with mesothelioma. Although a specific set of symptoms could not be identified yet due to the low number of documented cases, some signs which could indicate the presence of testicular mesothelioma are an abnormal lump in the testicles, pain, swelling and fluid buildup. This type of mesothelioma can thus easily be mistaken for one of the following diseases:

• carcinoma of the rete testis
• testicular germ cell tumors
• adenomatoid tumor
• epididymitis
• florid mesothelial hyperplasia

What Makes Mesothelioma so Difficult to Detect?

Diagnosing mesothelioma is very challenging for multiple reasons. There are numerous factors that may contribute to the disease being misdiagnosed as a more frequently occurring condition or even as another form of cancer with similar symptoms. Some of the most common reasons why mesothelioma fails to be recognized by oncologists are:

• Low prevalence. Only 3,000 people in the U.S. are diagnosed with mesothelioma every year, while lung cancer - which often mimics the symptoms of the former - represents the second most common malignant disease, with over 200,000 new cases annually. Consequently, the majority of oncologists do not encounter a single case of mesothelioma in their entire career.
• Complexity. Mesothelioma is a very intricate form of cancer. Although the disease has been extensively researched within the last three decades and its connection with asbestos exposure is undeniable, there are numerous aspects that are not completely clear to specialists.
• Inappropriate diagnostic methods. Because mesothelial tumors develop within the same regions of the body as more common malignant diseases, the results of X-rays and CT scans may mislead specialists in regards to the type of cancer the patient is suffering from. Thus, pleural mesothelioma might be mistaken for lung cancer. As these tests can only provide information about the location of the mass, more specific diagnostic procedures are required to detect mesothelioma.
• Generic symptoms. All types of mesothelioma are accompanied by a series of symptoms, which can easily be attributed to more common respiratory or gastrointestinal conditions.
• Fluid biopsy. Fluid biopsies are quite unreliable when it comes to diagnosing mesothelioma. Malignant cells are difficult to detect in a fluid sample collected from around the lungs or abdominal cavity and thereby, pathologists will often miss the disease completely. For an accurate diagnosis, a tissue biopsy is recommended, although the collecting process is more demanding.
• Cellular structure. Even a tissue biopsy can be misleading, as the malignant cells found in mesothelioma tumors often resemble the type of cells which occur in other forms of cancer and have a similar structure. Additionally, given the low prevalence of the disease, pathologists rarely have the chance to examine mesothelioma cells and thus may not be able to properly identify this cancer.
• Stage. When mesothelioma is properly identified and diagnosed, the stage of cancer can also be misjudged, resulting in the recommendation of ineffective treatment. As the most common type, pleural mesothelioma has a formal staging system, while oncologists need to conduct a very careful evaluation to correctly identify the stage of peritoneal, pericardial and testicular mesothelioma in the absence of a precise staging system.

Mesothelioma Is Not a Regular Lung Cancer

Both pleural mesothelioma and lung cancer development in the chest cavity and are accompanied by virtually the same symptoms. However, the two diseases are dissimilar in many respects. Although lung cancer can also be caused by prolonged exposure to asbestos, it is an entirely different form of cancer than mesothelioma. Distinguishing between lung cancer and pleural mesothelioma is crucial, as each malignant disease requires a very specific treatment regimen. Regrettably, it is not uncommon for mesothelioma to be misdiagnosed as lung cancer due to the similarities both types of cancer display, which results in numerous patients undergoing the wrong treatment.

It is essential to be aware of the main differences between pleural mesothelioma and lung cancer so as to prevent misdiagnosis. We have compiled a list of the clearest dissimilarities between the two forms of cancer which will hopefully help you avoid receiving an inaccurate diagnosis:

• Cause. While the sole known cause of mesothelioma is asbestos exposure, there are multiple factors that can lead to the development of lung cancer, including habitual tobacco smoking and exposure to pollutants such as radon, secondhand smoke, and diesel exhaust. However, it has been demonstrated that exposure to asbestos can significantly increase the risk of lung cancer as well.
• Location. Unlike lung cancer, which affects the tissue inside of the organs, pleural mesothelioma develops on the outer lining of the lungs (also known as pleura).
• Type of tumor. Lung cancer usually appears as a well-defined, individual mass of malignant cells, whereas mesothelioma has a diffuse nature and entails multiple small tumors occurring all across the surface of the pleura.
• Latency period. When exposure to asbestos is the primary cause, both lung cancer and pleural mesothelioma imply a long latency period. Nevertheless, while the former tend to appear within 10-30 years of the first contact with asbestos, pleural mesothelioma generally takes a longer time to develop and can occur in up to 50 years.
• Treatment. The appropriate treatments for lung cancer and pleural mesothelioma are extremely different. Thus, while lung cancer is typically treated with docetaxel, vinorelbine and paclitaxel chemotherapy, mesothelioma requires cisplatin and pemetrexed chemotherapy. Radiation therapy is employed in the treatment of both diseases. However, for pleural mesothelioma, it is used immediately after surgery to prevent the spreading of cancer, whereas radiotherapy mostly serves as a palliative treatment for patients diagnosed with lung cancer. Surgery is also specific to each form of cancer. Unlike surgery for lung cancer, during which a portion of the lung or the entire organ is removed, surgical treatment for pleural mesothelioma entails the removal of the pleura, the portions of the diaphragm affected by malignant cells, as well as a section of the lung.

Properly Diagnosing Mesothelioma

Choosing a board-certified oncologist specialized in mesothelioma cases who has vast experience in treating it is absolutely crucial to avoid misdiagnosis and gain access to appropriate treatment.

Mesothelioma has very rapid and aggressive progress and early diagnosis is vital. Detecting cancer in its early stages will not only provide you with the maximum treatment options available, but it can also substantially improve your prognosis and quality of life.

A mesothelioma specialist will promptly order a series of tests and examination procedures which will eventually reveal whether you suffer from mesothelioma or not. Nevertheless, it is important to know that the entire diagnostic process may take up to three months, as the oncologist will first try to eliminate common causes that might be responsible for your symptoms and you will have to undergo multiple tests for an accurate evaluation. The most relevant tests for mesothelioma include:

• CT scans and X-rays - your doctor will be able to identify the location of the tumor and see whether it has metastasized to other organs
• a tissue biopsy - in the process of diagnosing mesothelioma, tissue biopsies are significantly more reliable than fluid biopsies, as malignant cells can be more easily observed and evaluated this way
• the Mesomark test - this blood test is one of the most accurate methods of diagnosing mesothelioma and can also be used during treatment to monitor the progress of the disease
• the SOMAmer panel - another blood test which has proved to be quite reliable for detecting mesothelioma, with a high accuracy rate of approximately 93%
• the Human MPF Elisa Kit - the purpose of this blood test is to detect the presence of a soluble protein which is typically produced by mesothelin in the blood

Each of the above tests is performed by different medical professionals including radiologists and B-readers. Seeking a second opinion from a mesothelioma specialist is always a good idea and you should not hesitate to discuss your mesothelioma diagnosis with another oncologist. Second opinions are crucial when it comes to all types of cancer and are particularly more valuable when rare malignant diseases such as mesothelioma are suspected.