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What Is Cystic Mesothelioma?

Cystic mesothelioma is a benign form of mesothelioma that develops in the peritoneum, the layer of tissue that lines and protects the abdomen and abdominal organs. This disease, also known as benign multicystic peritoneal mesothelioma, does not usually cause cancer but can progress into an aggressive malignancy in some patients. The benign variant is more common and is considered an intermediate form of mesothelioma. Medical experts classify cystic mesothelioma as less dangerous than the diffuse epithelial variant but 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, unlike other subtypes of mesothelioma. 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, which revealed multicystic peritoneal mesothelioma during the biopsy.

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

Because cystic mesothelioma develops in the peritoneum of the abdomen and pelvis, most symptoms involve abdominal or pelvic pain, bloating or cramps. Other symptoms can include changes in urinary or bowel habits.

A case study of one patient in January 2022 reported on a 32-year-old woman who presented with abdominal pain. CT scans showed an inflamed lesion near her colon. She underwent surgery to remove the lesion, which revealed multicystic peritoneal mesothelioma during the biopsy.

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

According to a 2018 case report published in Case Reports in Surgery, most patients do not experience symptoms until the tumor is large enough to impact other organs

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Cystic Cells and Growth Patterns

Benign multicystic peritoneal mesothelioma is characterized by smooth, thin-walled cysts held together by fragile fibrovascular tissue. 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 considered a localized tumor.

Diagnosing Cystic Mesothelioma

It is difficult for doctors to diagnose cystic mesothelioma because of its rarity. Most people are diagnosed incidentally during a doctor’s visit for a different medical issue.

Patients often report pelvic or lower abdominal pain and weight loss as the first signs of the disease. After performing standard physical exams, doctors typically order an imaging scan to find out more 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

A CT scan, ultrasound or MRI can be used to visualize tumors, but these tests can’t confirm a diagnosis. 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.

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.

Misdiagnosis of Benign Multicystic Peritoneal Mesothelioma

When trying to pin down the correct diagnosis, it can be difficult for doctors who are not mesothelioma specialists to tell cystic mesothelioma apart from 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 instead of the liquid-filled cysts that develop from cystic mesothelioma. The cells in malignant mesothelioma tumors also display increased activity, which doctors can detect with immunohistochemical staining.

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Treatments for Cystic Mesothelioma

Surgery is the only highly effective treatment for cystic mesothelioma. A 2021 research article in the International Journal of Surgery Case Reports concluded that complete surgical excision of benign cystic mesothelioma must always be the first step of the treatment plan for this condition.

A 2022 case study in the International Journal of Surgery Case Reports described a 60-year-old woman treated with cytoreductive surgery followed by HIPEC. The authors suggested the treatment could be considered to treat peritoneal benign cystic mesothelioma and prevent its malignant transformation.

Because this type of cancer grows slowly 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. 

Despite the positive response to resection, about half of all patients will experience a recurrence. After diagnosis, patients must undergo routine follow-up imaging to monitor cancer progression.

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