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Benign Mesothelioma

Benign mesothelioma is a rare but treatable non-cancerous form of mesothelioma. Forming as tumors in the mesothelium, the membrane that lines the thoracic cavity. While a malignant tumor can metastasize or spread to other tissues, benign tumors may grow but do not spread.  Thankfully, the majority of tumors found in mesothelial tissues are not malignant.

Diagnosing benign mesothelioma is similar to malignant tumors. However, it usually requires a biopsy for a doctor to determine if cells benign not malignant. Treatment is straightforward, usually involving surgery to remove the tumor. Generally, prognosis for this condition is generally very good.

Malignant vs. Benign Mesothelioma

The main difference between these types of tumors is that malignant mesothelioma has the potential to spread to other tissues. In contrast, a benign tumor does not. Mesothelioma as a type of cancer is rare as a type of cancer, but benign tumors of the mesothelium are even more rare. Also, malignant mesothelioma is strongly connected to asbestos exposure, while the benign form seems to be completely unrelated.

There are several sub types of each kind of mesothelioma. Benign tumors can come in different forms including benign tumors of the pleura, benign multicystic peritoneal mesothelioma, and papillary mesothelioma. Of these, benign tumors in the pleura are most common. The peritoneal form is rare, with only about 150 cases ever reported, and papillary mesothelioma has only been reported approximately 60 times.

Benign Fibrous Pleural Mesothelioma

The most common of these rare benign mesotheliomas forms in the pleura, or the lining of the lungs. In 2004, approximately 500 cases of benign mesothelioma in the pleura were reported. Most of these tumors first grow in the visceral layer of the pleura, the inner layer surrounding the lungs. Benign pleural tumors can range from small to large, are typically smooth, may have fluid-filled cysts, and are often partially calcified. Tumor cells may be fibrous, cellular, mixed, or a combination of fibrous and cellular.

Benign Multicystic Peritoneal Mesothelioma

Even less common is the type of benign mesothelioma that originates in the peritoneum, the epithelium that lines abdominal organs. This type is most common in women of reproductive age although it can occur in both sexes and at any age. Benign peritoneal mesothelioma is usually multicystic, meaning they contain multiple, fluid-filled cysts.

Well-Differentiated Papillary Mesothelioma

Very few cases of well-differentiated papillary mesothelioma have been diagnosed and reported. They are mostly benign tumors, although some also have malignant cells. They are more common in women between the ages of 30 and 40 and are most likely to arise in the peritoneum. In a few cases, these tumors have developed in the pericardium, the lining around the heart. Papillary mesothelioma tumors are characterized by papillary structures, which can only be seen under the microscope.

Adenomatoid Tumors

Adenomatoid tumors are often seen in the testis or uterus. These tumors are often classified as benign mesotheliomas because they originate in the mesothelium that surrounds the glands. It is possible for this type of tumor to become malignant. However, they are most often benign and can be found in the pleura or peritoneum as well as in the testis and uterus.


Although benign tumors are noncancerous and do not spread to other tissues, they can create problems as they increase in size. Benign pleural tumors, for instance, can cause some of the same symptoms as malignant pleural mesothelioma. These symptoms include tightness in the chest, shortness of breath, chest pains, and pleural effusion (the buildup of fluid between the two layers of the pleura). If the tumor is a significant size, it can ultimately cause more serious complications including seizures and coma.

Benign mesothelial tumors of the peritoneum or pericardium may cause similar complications. Complications usually occur when the tumor has grown large enough to cause fluid buildup, resulting in pain or discomfort. In many cases of peritoneal or pericardial benign tumors, there are no symptoms. The tumor may be found coincidentally if the patient is being screened for something else.


Diagnosis for benign mesotheliomas may be accidental if no symptoms are apparent. However, in some cases the tumor grows large enough to cause discomfort. Diagnosis begins with a physical exam and continues with imaging scans. These scans may indicate an unusual mass or lesion, which is expected to be a tumor.

The next step is to determine whether mass is a benign or malignant tumor, whether it is a mesothelioma, and what cell types are involved. A pathologist can examine the biopsied tumor sample under a microscope to determine if the cells are benign. He or she can also determine if the biopsied tissue is of a papillary or adenomatoid type.

This histological approach is not always accurate, but immunohistochemical staining can improve that accuracy. This technique uses antibodies to target specific antigens in tumor cells. It can rule out or find cancerous cells with good accuracy.


If there are no symptoms and a benign mesothelial tumor is small, it may not require treatment. If mor is increasing in size and causing discomfort, the typical treatment is surgery to remove the mass. Treatments are straightforward surgeries with modest recovery periods. In some cases of benign pleural mesothelioma, a segment of a lung or an entire lobe may need to be removed. This will require more recovery time, and increases the possibility of complications.


The prognosis for benign mesotheliomas is overwhelmingly positive, but, as with surgery, there are risks. However, surgical removal of one of these tumors is completely curative. Some patients may experience a recurrence, but recurrence is typically benign and occurs years later. Survival rates of benign mesothelioma are near 100 percent.

Page Edited by Dave Foster

Dave has been a mesothelioma Patient Advocate for over 10 years. He consistently attends all major national and international mesothelioma meetings. In doing so, he is able to stay on top of the latest treatments, clinical trials, and research results. He also personally meets with mesothelioma patients and their families and connects them with the best medical specialists and legal representatives available. Connect with Patient Advocate Dave Foster

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