Table Of Contents

What Is Benign Mesothelioma?

Benign mesothelioma is a non-cancerous growth in the lungs. Unlike asbestos-related cancers, including malignant mesothelioma, doctors aren’t always sure what causes benign mesothelioma. 

There are several types of benign mesothelioma, and each is rarer than malignant mesothelioma. For example, benign multicystic peritoneal mesothelioma has less than 200 reported cases. Another benign type, called well-differentiated papillary mesothelioma,has just 180 documented cases.

Fortunately, effective treatment and a full recovery are possible for most people with benign mesothelioma. However, if tumors return, they may become malignant. For this reason, doctors must continue to monitor for new tumors.

Benign Mesothelioma vs. Malignant Mesothelioma

Malignant mesotheliomas tend to surface 20 to 50 years after asbestos exposure, while benign mesothelioma can occur at any age. 

Doctors can determine if mesothelioma is benign or malignant by examining a sample of tumor cells (known as a biopsy) under a microscope and running diagnostic tests.

A solid, single tumor mass in the lining of the lungs (mesothelium) may indicate benign mesothelioma. Conversely, many small tumors on the lung lining are more likely malignant. However, benign multicystic peritoneal mesothelioma causes several growths in the peritoneum (abdominal cavity) much like the malignant version.

Benign vs malignant mesothelioma tumor characteristics

A key difference between benign and malignant tumors is that benign tumors do not invade nearby tissues, and they generally do not spread to other parts of the body. For this reason, benign mesothelioma is much less dangerous than malignant mesothelioma, though benign tumors can still cause complications and discomfort.

Symptoms of Benign vs. Malignant Mesothelioma

In general, symptoms of benign mesothelioma are similar to the symptoms of malignant mesothelioma. Most people with benign mesothelioma of the pleural lining experience shortness of breath, chest pain and a chronic cough. People with malignant pleural mesothelioma experience these same symptoms but commonly show additional symptoms such as fever, night sweats and weight loss.

Benign tumors can grow large enough to negatively impact nearby tissues and organs. For example, benign pleural fibrous tumors in the lining of the lungs can cause fluid buildup, low blood sugar, and rarely, seizures or coma.

Benign mesothelioma symptoms may also be more ambiguous in some cases. A 2021 case described a 25-year-old woman with constipation, urinary urgency and irregular menstruation. This case study highlighted the challenges of diagnosing certain types of benign mesothelioma.

Diagnosing Benign Mesothelioma

The diagnostic process for benign mesothelioma includes reviewing medical history and performing a physical exam. If a problem is suspected, the doctor will recommend a series of tests, such as:

  • Imaging Scans: X-rays, CT scans and MRI scans may identify suspicious tissue. Imaging helps pinpoint the location of potential tumors, which is helpful for biopsy testing and surgical treatment.
  • Blood Tests: While blood tests cannot diagnose benign or malignant mesothelioma, they can help reveal whether cancer is present.
  • Biopsies: A biopsy collects a sample of cells for analysis under a microscope. Biopsies are the only way doctors can confirm whether a tumor is benign or malignant.

A biopsy also shows the cell type that makes up the benign tumor. This information is helpful because certain types are at low risk of becoming malignant mesothelioma.

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Types of Benign Mesothelioma 

There are several benign mesothelioma types defined by the cell characteristics of the tumors. Unlike malignant versions, benign tumors respond well to treatment, which is good news for patients.

  • Benign Multicystic Peritoneal Mesothelioma (BMPM): This type occurs in the peritoneal cavity, most often in the pelvis. It typically affects young and middle-aged women, though it can also develop in men and children. Symptoms include abdominal pain and swelling. BMPM sometimes occurs in women who have had previous abdominal surgery.
  • Adenomatoid Tumor (AT): AT is a subtype of epithelial mesothelioma. It most commonly affects the uterus wall and membrane of the pouch that covers the testes. It is rare for this type to develop in the pleura.
  • Localized Fibrous Tumor (LFT): LFT affects the surface of mesothelial cells in the pleura, though it can also occur in the pericardium (the membrane around the heart), tunica vaginalis and peritoneum. About 50% of patients experience no symptoms, but when symptoms occur, they include cough, pain and breathlessness.
  • Well-Differentiated Papillary Mesothelioma (WDPM): WDPM is usually benign, but there have been some recorded instances of malignant cells mixed in with benign cells. Most cases occur in the peritoneum of women 30 to 40 years of age. WDPM may also affect the lining of the lungs, heart and testes. Symptoms include pain and fluid accumulation in these linings.

WDPM has shown the greatest chance of becoming malignant of these benign tumor types. In general, all patients with benign types are monitored after treatment to check for signs of the tumors returning.

Benign Mesothelioma Treatments

Benign mesothelioma is primarily treated with surgery. Tumors in the abdominal lining may also be treated with heated chemotherapy to reduce the rate of recurrence.

Recurrence of benign pleural mesothelioma is less common in pleural cases than in peritoneal cases. About 3% of pleural cases recur, and about half recur in peritoneal cases without heated chemotherapy. 

Benign Pleural Mesothelioma Treatment

When benign mesothelioma develops in the lung lining, a surgical procedure called a thoracotomy is commonly performed. The details of surgery depend on the size and location of the tumor. A thoracotomy may involve the removal of a segment of the lung, a lobe or even the entire lung. However, removal of the entire lung is infrequent in benign cases.

Although benign pleural mesothelioma is controllable, complications may develop following surgery. The most common side effect of surgery is pleural effusion, a fluid buildup in the pleural spaces that puts pressure on the lungs and heart. Patients are usually fitted with a chest drain for the first few days after surgery to remove excess fluid and prevent effusion. 

Benign Peritoneal Mesothelioma Treatment

In the past, benign mesothelioma in the abdominal lining usually required a surgical procedure called a laparotomy or laparoscopy to remove the growth. Unfortunately, the tumors often returned, especially in women. Women showed a recurrence rate of 40% to 50%, while men had a 33% recurrence rate after surgery.

Today, benign peritoneal mesothelioma is treated with surgery to remove growths from the abdominal cavity (cytoreductive surgery) and heated chemotherapy. This combination approach has reduced the rate of recurrence to about 20%. 

As doctors continue to learn more about benign mesothelioma treatments, there’s hope that the condition will continue to pose minimal threat to patients.

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