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What is Benign Mesothelioma?

Unlike asbestos-related cancers, including malignant mesothelioma, the benign form is not cancerous and not the result of asbestos exposure. Whereas the malignant type tends to surface 20-50 years after asbestos exposure, benign mesothelioma can occur at any age.

There are several types of benign mesothelioma, and each is rarer than malignant mesothelioma. Benign multicystic peritoneal mesothelioma, for example, has only 153 cases reported in medical literature. Well-differentiated papillary mesothelioma, another benign type, has fewer than 60 documented cases.

In contrast to malignant mesothelioma, which has an extremely high mortality rate, effective treatment and full recovery are possible for most people who are diagnosed with benign mesothelioma. However, there have been instances of tumor recurrence, and sometimes the relapse is malignant. For this reason, doctors usually continue to monitor patients for new tumors.

Benign vs. Malignant

Tumors form when previously healthy cells begin rapid division and form a solid lump of cells. It is important to note that benign tumors are not cancerous. The term “cancer” only refers to malignant tumors.

The key differences between benign and malignant tumors are that benign tumors do not invade nearby tissues and they do not spread to other parts of the body. For this reason, benign mesothelioma is much less serious than malignant mesothelioma, though complications and discomfort can still arise from benign tumors.

These tumors can grow large enough to have a negative impact on the tissues and organs around them. For example, benign pleural fibrous tumors in the lining of the lung can cause fluid buildup and may cause more serious side effects such as low blood sugar, which can rarely result in seizures, or coma.

Benign mesothelioma symptoms may also be more ambiguous, such as in the case of a 25-year-old woman who presented with constipation, urinary urgency, and irregular menstruation. The 2021 case study highlighted the difficult diagnosis of intraperitoneal cystic masses and was published in the Annals of Medicine and Surgery.

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

Benign vs malignant mesothelioma tumor characteristics

The diagnostic process for benign mesothelioma is similar to that for the malignant version. Patients must provide complete medical histories and undergo physical examinations. If a problem is suspected, the doctor will recommend one or more imaging tests.

Imaging tests, which are used to locate the tumors, include the following:
  • Chest X-rays
  • CT scans
  • MRI scans

The doctor may also recommend biopsy procedures. A tissue biopsy involves removing a sample of suspected tumor cells from the affected area, whereas a fluid biopsy (also called needle aspiration) involves the insertion of a long needle into the suspected tumor to remove fluid.

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Types of Benign Mesothelioma

There are several types of benign mesothelioma, differentiated by cell characteristics. Unlike the malignant version, these benign tumors are fairly simple to treat and prognosis is usually good.

Benign Multicystic Peritoneal Mesothelioma (BMPM)
  • Occurs in the peritoneal cavity (most often in the pelvis).
  • Typically occurs in young and middle-aged women, though it can also develop in men and children.
  • Symptoms include abdominal pain and swelling.
Well-Differentiated Papillary Mesothelioma (WDPM)
  • Usually benign, but there have been some recorded instances of malignant cells mixed in with the benign ones.
  • The majority of cases occur in the peritoneum (abdominal cavity) of women 30 to 40 years of age.
  • May also occur in the pericardium (heart sac), pleura and tunica vaginalis (testicular lining).
  • Symptoms include pain and effusions (fluid accumulation).
Adenomatoid Tumor (AT)
  • Most commonly affects the tunica vaginalis and the uterus wall.
Localized Fibrous Tumor (LFT)
  • Affects the surface of mesothelial cells in the pleura, though can also occur in the pericardium, tunica vaginalis and peritoneum.
  • About 50 percent of patients experience no symptoms, but when symptoms occur, they include cough, pain and breathlessness.

Of these benign tumor types, WDPM has the greatest chance for becoming malignant.

Quick Fact:
BMPM sometimes occurs in women who have had previous abdominal surgery.

Benign Mesothelioma Treatments

In most cases of benign mesothelioma, the only treatment needed is a surgical procedure to remove the tumor. In contrast to malignant mesothelioma, there is no need for follow-up treatment such as chemotherapy since the tumor is not cancerous and has not spread. In some cases, the patient may need to be monitored for re-occurrence.

75% of people with benign mesothelioma develop tumors.
A total of 75 percent of individuals with benign mesothelioma develop tumors in the lung

Because approximately 75 percent of individuals with benign mesothelioma develop tumors in the lung, a surgical procedure called a thoracotomy is commonly performed. The exact nature of the procedure depends on the size and location of the tumor. Thoracotomy may involve removal of a segment of the lung, a lobe or even the entire lung. However, removal of the entire lung is very rare in benign cases.

Although benign mesothelioma itself is a relatively harmless disease, 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.

Following surgical treatment, most people experience complete recovery.

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