What Is Cystic Mesothelioma?

Cystic mesothelioma is a benign form of mesothelioma. It develops in the peritoneum, the layer of tissue that lines the abdominal organs. It is also known as benign multicystic peritoneal mesothelioma.

This disease is not considered cancer. But it can progress into an aggressive malignancy in some patients. The benign variant is more common and an intermediate form of mesothelioma.

Medical experts classify cystic mesothelioma as less dangerous than the diffuse epithelial variant. But it is more severe than localized benign adenomatoid mesothelioma.

Distribution of cystic mesothelioma diagnoses
Distribution of cystic mesothelioma diagnoses.

Most cases develop in the pelvic peritoneum (the lining of the lower abdominal cavity) of women under 40. Most other subtypes of mesothelioma develop in men. These lesions can also develop in pelvic structures such as the omentum, uterus, bladder and rectum. In unusual cases, it can also grow in the liver.

A case study from January 2022 reported on a 32-year-old woman who presented with abdominal pain. CT scans showed a lesion with surrounding inflammation near her colon. She underwent surgery to remove the lesion. The biopsy revealed multicystic peritoneal mesothelioma.

Unlike malignant mesothelioma, the link between asbestos exposure and cystic mesothelioma is unclear. Some studies suggest cystic mesothelioma develops in response to foreign fibers and dust. Another possible cause is chronic irritation, such as prior surgery or endometriosis. Other studies suggest that female sex hormones can trigger its development.

Symptoms of Cystic Mesothelioma

Most symptoms involve abdominal or pelvic pain, bloating or cramps. Other symptoms can include changes in urinary or bowel habits.

Common symptoms of benign multicystic peritoneal mesothelioma include:
  • Abdominal pain
  • Abdominal fullness
  • Change in bowel habits
  • Feeling full after eating a small amount of food
  • Intestinal obstruction
  • Pelvic pain
  • Weight gain

Most patients do not experience symptoms until the tumor is large enough to impact other organs. A 2018 case report published in Case Reports in Surgery confirmed this factor.

Cystic Cells and Growth Patterns

Smooth, thin-walled cysts characterize benign multicystic peritoneal mesothelioma. Fragile fibrovascular tissue holds the cysts together. The individual cells are flat or cube-shaped. 

The cysts can fill with mucinous or gelatinous fluid and may grow as large as 20 cm in diameter. On imaging scans, doctors may be able to see separate “chambers” in the cystic tumor. When removed from the body, the tumors may appear pale yellow.

Unlike many types of cancer, cystic peritoneal mesothelioma does not spread or metastasize to other body systems. It is a localized tumor.

Diagnosing Cystic Mesothelioma

The best way to diagnose cystic mesothelioma is by performing a biopsy with a laparoscopy technique. This minor surgical procedure uses a thin tube fitted with a light and camera. A CT scan, ultrasound or MRI can visualize tumors, but these tests can’t confirm a diagnosis.

Patients often report pelvic or lower abdominal pain and weight loss as the first signs of the disease. Doctors perform a standard physical exam. They also order imaging scans to learn about the underlying cause of these symptoms.

Other names for a cystic mesothelioma diagnosis include:
  • Benign multicystic peritoneal mesothelioma
  • Benign papillary peritoneal cystosis
  • Postoperative peritoneal cysts
  • Multilocular peritoneal inclusion cysts

Doctors can spot abnormal growths and collect tissue samples through a small incision in the abdomen. The tissue is then sent to the lab for testing, where a pathologist, a doctor specializing in cellular changes, can confirm a diagnosis.

It is difficult for doctors to diagnose the disease because of its rarity. The diagnosis often develops from a doctor’s visit for a different medical issue.

Misdiagnosis of Benign Multicystic Peritoneal Mesothelioma

Doctors who are not mesothelioma specialists may misdiagnose it. Cystic mesothelioma looks like malignant mesothelioma and other types of benign growths. There are a few ways to distinguish between cysts that look similar.

Malignant mesothelioma typically forms calcified plaques or nodules. Cystic mesothelioma forms liquid-filled cysts. The cells in malignant mesothelioma tumors also display increased activity. Doctors detect this with immunohistochemical staining.

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Treatments for Cystic Mesothelioma

Surgery is the only effective treatment for cystic mesothelioma. Complete surgical removal of benign cystic mesothelioma is the first step of the treatment plan. A 2021 article in the International Journal of Surgery Case Reports confirmed this.

A 2022 case study described a woman treated with cytoreductive surgery followed by HIPEC. The treatment could treat peritoneal benign cystic mesothelioma and prevent its malignant transformation.

Because this type of cancer grows slow and does not spread, its prognosis is much better than other forms of the disease. As of 2009, only one patient had died from the benign variation of the condition, and this patient had elected not to undergo surgical resection. 

About half of all patients will experience a recurrence. After diagnosis, patients must undergo routine follow-up imaging to monitor cancer progression.