Benign mesothelioma is a rare, non-cancerous form of mesothelioma comprised of four subtypes that affect both men and women.
Unlike other forms of the disease, there is no direct link between benign mesothelioma and asbestos exposure, though other risk factors have emerged. There have been limited documented cases of each subtype, with fewer than 200 cases of benign multicystic peritoneal mesothelioma (BMPM), fewer than 60 diagnosed cases of well-differentiated papillary mesothelioma (WDPM) and fewer than 25 reported cases of benign adenomatoid tumors (AT) and local fibrous tumors (LFT). Growth and prognosis vary based on subtype, but prognosis is generally favorable for benign mesothelioma patients, with curative surgery as the main treatment option.
Benign Cell Structure
The cell structure of benign mesothelioma tumors differs based on type. However, most subtypes are composed of epithelial cells. Epithelioid cells are noted for growing in clusters, and are much slower to metastasize compared to other cell types. Epithelial cells are also the most responsive to treatment and offer a better prognosis.
A defining characteristic between benign mesothelioma and malignant mesothelioma is how the disease progresses. Malignant mesothelial cells invade tissues and can spread to other areas of the body, affecting organs and lymph nodes, and limiting treatment options. Benign mesothelioma cells do not invade or spread, allowing for complete surgical resection.
Rare Benign Cell Types
Benign mesothelioma is rarer than the malignant form, leading to a limited number of cases. Based on the cases that have accumulated, four rare subtypes have been established. While most cases are benign, some of these subtypes can also manifest as malignant cells.
- Benign Multicystic Peritoneal Mesothelioma: Also referred to as benign multicystic mesothelioma, benign cystic mesothelioma, and BMPM, this type of peritoneal mesothelioma is most common in women of reproductive age, with only 20 reported cases in men. Women with a history of endometriosis, pelvic inflammatory disease or surgeries may be more at risk. Studies have found a recurrence rate of about 50% with potential for malignancy.
- Well-Differentiated Papillary Mesothelioma: WDPM is an uncommon, non-cancerous tumor typically found in women. Most cases are asymptomatic, though pain and swelling have been reported. This type of mesothelioma is most common in the peritoneum, with rare instances in the pericardium, pleura and tunica vaginalis. Recurrence rates are low.
- Adenomatoid Tumors: An adenomatoid mesothelioma tumor (AT) is slow-growing and non-cancerous, affecting both men and women. This form of mesothelioma typically develops within testicular linings, the uterus wall, fallopian tubes and other reproductive organs. In most cases, these tumors are asymptomatic and found accidentally during routine examinations.
- Localized Fibrous Tumors: Also referred to as benign fibrous mesothelioma, LFT can develop in men and women. Case reports have found that about half of patients experience symptoms, while half are asymptomatic. These tumors are mostly found in the pleura, but have been seen in the pericardium, tunica vaginalis and peritoneum in rare cases.
Diagnosing Benign Mesothelioma
Every case of benign mesothelioma manifests differently, and a patient’s overall health and age can affect the presence or severity of symptoms. With a limited number of cases, it’s difficult to pinpoint common symptoms of benign mesothelioma, and many patients experience no symptoms. In some instances, they may mimic symptoms of malignant mesothelioma, like chest pain, abdominal pain, weight loss, chronic cough and pleural effusion. Any potential symptoms should be addressed immediately.
If mesothelioma is suspected, a doctor will look at the patient’s history and symptoms, and will also conduct a variety of tests to determine the presence of mesothelioma, if it is malignant or benign, and mesothelioma type.
Diagnostic testing will include imaging tests like CT scans, X-rays and MRI scans, followed by biopsies to definitively classify the disease as benign or malignant. Doctors use a biopsy to analyze tumor cells under a microscope and identify cell size and shape, nucleus size and shape and cell arrangement. These characteristics show whether a cell is benign or cancerous and will also allow the physician to determine cancer type and whether or not the cancer has spread.
|Malignant Mesothelioma||Benign Mesothelioma|
|Common treatment: Multimodal approach of surgery, chemotherapy and/or radiation||Common treatment: Curative surgery|
|Metastasis: Aggressive||Metastasis: None, but potential for local recurrence|
|Organ and tissue damage: Damage to nearby tissues and organs with potential for distant damage||Organ and tissue damage: Typically none|
Determining malignancy will be a driving factor in a patient’s treatment plan and prognosis. Early detection of malignant mesothelioma is important to giving patients the best treatment options possible, and if benign, curative surgery has shown high success rates in treating patients, offering a full recovery without need for additional treatment.
Benign Mesothelioma Prognosis
Life expectancy is generally unaffected by a benign mesothelioma diagnosis, and most patients are able to live a full life after the tumor is removed. However, recurrence is possible, especially for benign multicystic peritoneal mesothelioma. Tumors can return as malignant, which would then present patients with a very poor prognosis depending on the stage of cancer and location. On average, malignant mesothelioma patients survive 12 to 21 months.
Survival rates vary widely depending on the subtype of mesothelioma, and if patients face a malignant recurrence.
- For multicystic peritoneal mesothelioma, studies have found a 5-year survival rate of 90% progression-free and 10-year survival rate of 72% without disease progression.
- Well-differentiated papillary mesothelioma has fewer reported case studies, so data for survival rates and rate of recurrence is limited. However, one study found a 10-year survival rate of 30.8% for patients with WDPM.
- Researchers have found an average prognosis of about 10 years for patients diagnosed with malignant adenomatoid tumors, also with limited case studies.
- With limited data, life expectancy for malignant localized fibrous tumors is unclear. With a high frequency of misdiagnosis, patients often face limited treatment options and a poor life expectancy, with some patients surviving less than one year if tumors are composed of sarcomatoid cells.
To ensure a high quality of life and early detection of recurrent, malignant tumors, patients should have frequent monitoring and follow up appointments after completing benign mesothelioma treatment.
Treatment Options for Benign Mesothelioma
Treatment for benign mesothelioma is typically straightforward, consisting of curative surgery to fully remove the tumor. Surgical treatment for malignant mesothelioma is typically done in combination with chemotherapy and radiation to remove as much of the cancer as possible, but doesn’t cure the disease. It is also used palliatively to improve symptoms and quality of life for patients with more advanced disease. In contrast, the goal of surgical treatment for benign mesothelioma is to cure the disease.
Surgery does pose some risks and requires recovery, all of which should be discussed with a mesothelioma specialist. Studies have also shown that it’s crucial for physicians to avoid overtreatment, imposing unnecessary treatment measures on a benign disease. For example, radiation from repeated image testing or radiation done to shrink a non-cancerous tumor could cause long-term damage to nearby organs and tissues. Patients and their loved ones should discuss treatment options and potential risk factors with their physician to ensure the best treatment plan.
Author: Linda Molinari
Editor in Chief, Mesothelioma Cancer AllianceRead about Linda
Reviewer: Dr. James Stevenson
Medical Reviewer and Thoracic Medical OncologistRead about Dr. Stevenson
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