Written by Karen Selby, RN | Medically Reviewed By Dr. Andrea Wolf | Edited By Walter Pacheco

What Is Benign Mesothelioma?

Benign mesothelioma is a noncancerous growth in the lung lining or abdominal lining. Benign tumors do not invade other tissues or spread to other areas of the body like malignant tumors. Benign mesothelioma tumors grow at a slower rate. They tend to form a singular mass rather than the many tumor nodules seen in malignant cases.

Researchers have identified 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 tumor, has 180 documented cases.

Benign versus Malignant Mesothelioma Graphic

Doctors aren’t sure what causes benign mesothelioma. The history of asbestos exposure in people with benign mesothelioma is not well-documented. At least 80% to 90% of people with malignant mesothelioma have a history of asbestos exposure.

People with benign and malignant mesothelioma tumors share certain symptoms such as abdominal pain and shortness of breath. Patients with malignant mesothelioma are more likely to experience weight loss, while those with benign tumors tend to experience weight gain. 

Effective treatment and 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 watch for new tumors. Accurate diagnosis and treatment planning are crucial for optimal outcomes in cases of benign mesothelioma.

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 mesotheliomas can occur in the lining of the lung, heart, abdomen and testes. The most common type is benign multicystic mesothelioma.

Benign Mesothelioma Types
  • 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.
  • 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.
  • Localized Fibrous Tumor (LFT): LFT affects the surface of mesothelial cells in the pleura. 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 Tumor (WDPT): WDPT 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. WDPT may also affect the lining of the lungs, heart and testes. Symptoms include pain and fluid accumulation in these linings.

WDPMT 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.

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Benign Mesothelioma Symptoms

In general, symptoms of benign mesothelioma are similar to the symptoms of malignant mesothelioma. Benign tumors can grow large enough to negatively impact nearby tissues and organs. Symptoms vary depending on the affected organ, and may affect tissues in the chest, abdomen or pelvis.

Common Benign Mesothelioma Symptoms
  • Abdominal pain
  • Chest pain
  • Chronic cough
  • Fluid buildup
  • Palpable masses
  • Shortness of breath
  • Weight gain

Benign pleural tumors may also cause low blood sugar and, rarely, seizures or coma. People with malignant pleural mesothelioma experience these same symptoms. They also show additional symptoms such as fever, night sweats and weight loss.

When benign mesothelioma forms in the abdomen, the condition may cause abdominal swelling or distention and tenderness. Palpable masses within the abdomen or pelvis may be present.

Benign mesothelioma symptoms may also be more ambiguous in some cases. A 2021 report documented a 25-year-old woman with unusual symptoms. They included 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 a physical exam, medical history, blood tests, imaging scans and biopsy. The most important tool is a biopsy because it shows whether a tumor’s cells are benign or malignant.

Diagnostic Tools
  • 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.
  • Blood Tests: Blood tests cannot diagnose benign or malignant mesothelioma, but they may help reveal whether cancer is present.
  • Imaging Scans: X-rays, CT scans and MRI scans may identify suspicious tissue. Imaging helps pinpoint the location of potential tumors. It is helpful for biopsy testing and surgical treatment.

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

Prognosis for Benign Mesothelioma

The prognosis for benign mesothelioma is favorable, especially when the tumor is completely surgically removed. Recurrences are common but can be managed with another surgery. In some cases, a more aggressive surgical approach is necessary. Surgery may be combined with heated intraperitoneal chemotherapy for abdominal cases.

Doctors have identified a few risk factors for recurrence. Recurrence has been more common among cases that develop in the abdomen. Incomplete surgical removal can lead to local recurrence.  

Life expectancy for patients is generally unaffected by benign mesothelioma because the disease responds well to surgical management. Most people can live a full, unrestricted life following surgical treatment.

The only words of advice I have to anyone fighting cancer of any kind is to keep hope, stay strong and positive and express your feelings. Do not be afraid to ask questions, and call your doctor’s medical assistant every day if you have to. You have to learn to laugh, and keep your humor.

Unfortunately, a small chance of malignant transformation is possible. People with the condition should be aware of the possibility of recurrence and the rare chance of progression to malignancy. A biopsy can identify if a benign mesothelioma tumor has turned malignant.

Factors that can influence prognosis include the patient’s age, gender, malignant transformation and family history of developing these tumors. Other factors include a history of abdominal surgeries, alcohol use and smoking.

Benign Mesothelioma Treatments

Benign mesothelioma is primarily treated with surgery. Tumors in the abdominal lining may also be treated with heated chemotherapy during surgery. This helps reduce the rate of recurrence. Postoperative systemic chemotherapy is generally not recommended.

80%

The percent of multicystic peritoneal patients remaining disease free 10 years after surgery with heated chemotherapy.

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

It’s important to understand the potential risks associated with surgery. For example, fluid buildup after surgery may require the installation of a chest drain to prevent effusion.

Benign Pleural Mesothelioma Treatment

A surgical procedure called a thoracotomy treats benign pleural mesothelioma. 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

Doctors use the same treatments for both benign and malignant peritoneal mesothelioma. Benign cases treated with this aggressive approach have a high rate of long-term survival.

Surgeons use cytoreductive surgery to remove growths from the abdominal cavity. Heated chemotherapy follows the surgery. This combined procedure has reduced the rate of recurrence to about 20%.

In the past, laparotomy or laparoscopy removed 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. 

Benign Mesothelioma vs. Malignant Mesothelioma

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

Doctors can determine if mesothelioma is benign or malignant by looking at tumor cells under a microscope. A biopsy is the only test that differentiates benign mesothelioma from malignant mesothelioma.

Benign vs malignant mesothelioma tumor characteristics

A solid, single tumor mass in the lining of the lungs (mesothelium) may show benign mesothelioma. Many small tumors on the lung lining are more likely malignant. But benign multicystic peritoneal mesothelioma causes several growths in the peritoneum (abdominal cavity).

Malignant mesotheliomas tend to surface 20 to 60 years after asbestos exposure. Benign mesothelioma can occur at any age.

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