Introduction:
The cells and tissues in the human body are prone to unwanted growth. As a result, a mass of tissue or cells can occur in the form of tumors. These tumors can be benign (non-cancerous) or malignant (cancerous). Benign growths in the body include cysts, abscesses, tumors, etc., each with its pathology. Diagnosing benign growths can be tricky as multiple lesions in the body can resemble and present similar symptoms. Cysts are usually abnormal sacs or pocket-like tissues that contain air or fluid. Abscesses are identical to cysts, but the former contains pus or infected fluid. Read this article to know more about a rare cyst called the mesothelial cyst.
What Is Mesothelial or Mesothelium?
Tissue or cells derived from the mesoderm, a tissue that lines the body’s cavities of the embryo and later gives rise to muscles and other structures.
What Is a Mesothelial Cyst?
A mesothelial cyst is an extremely rare cyst lined by mesothelial cells. They are also called the primary retroperitoneal (behind the tissue that lines the abdominal wall) cyst of mesothelial origin. The cyst is so rare that only a few confirmed cases have been reported in the medical literature. The mesothelial cyst is usually found to be attached to the surface of visceral organs. It commonly occurs in women (84% of the cases) who belong to the reproductive age. In addition, some cases have been reported in patients with a history of abdominal surgery, pelvic inflammation, and appendicitis.
Why Does a Mesothelial Cyst Develop?
Three theories have been proposed to explain the origin of mesothelial cysts.
1. Developmental Disorder - During the 7th week of fetal development, there might be some flaws in the canal of the Nuck (abnormal patent pouch of parietal peritoneum extending from the uterus).
2. Inclusion of Embryonic Mesenchyme - The second theory states that the mesothelial remnants contribute to cyst formation during development.
3. De Novo Development of the Cyst - Attributes that the cyst develops from the beginning as an independent lesion.
What Are the Symptoms of a Mesothelial Cyst?
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The cyst can occur in adults or children and be asymptomatic in the initial stages.
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Long-standing lesions might cause chronic abdominal pain.
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Sometimes patients might experience acute pain secondary to torsion of the cyst.
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If the cyst ruptures, bleeding might occur.
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Secondary infection might occur.
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Large lesions might obstruct the gastrointestinal system.
How Is a Mesothelial Cyst Diagnosed?
Diagnosing mesothelial cysts only based on clinical findings is quite challenging. They usually do not show any signs or symptoms. Even if symptoms are present, they are milder compared to other lesions. Patients might experience discomfort or the presence of a mass in the abdomen. Clinicians should rule out other conditions like hernias to establish the diagnosis. Although the cyst affects mostly women of reproductive age, it does not seem to depend on sex hormones and stains negative for estrogen and progesterone.
Hernias Versus Mesothelial Cyst:
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Doctors perform a Valsalva maneuver (forcefully breathing by closing the mouth and pinching the nose while expelling the air out); if an inguinal mass or hernia is present, it disappears when the patient lies down on the back.
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As the enlarged uterus pushes the intestines during pregnancy, the hernia is not visible.
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Additionally, the veins tend to have varicosities during pregnancy due to increased intraabdominal pressure. This should be ruled out during the diagnosis.
Imaging Modalities:
1. Ultrasound (USG) - It is a safer choice compared to other imaging techniques, such as CT (computed tomography) and magnetic resonance imaging (MRI). In young women and children, using ultrasound prevents the danger of radiation. In addition, ultrasound shows real-time images, and changes in the intestines, blood vessels, and cysts can be visualized when subjected to pressure changes (coughing or Valsalva maneuver).
Various ultrasound appearances of the cyst include:
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Comaform.
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Fusiform.
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Oval cystic.
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Oval cystic with septa.
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Multilobular.
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Pedunculate (stalk-like structure connected to the peritoneal cavity).
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Solid cysts.
2. Computed Tomography (CT) - CT scan reveals a mass with an irregular thick wall of solid parts. The chances of misdiagnosing the cyst as cancer are high if the patient has a history of malignancy.
3. Magnetic Resonance Imaging (MRI) - This scan provides more details of the lesion and surrounding structures. The findings reveal a dark hyperintense border with cystic septations.
4. Biopsy - A biopsy can provide definitive confirmation of the cyst. A piece of the cystic tissue is removed and studied under a microscope. The cyst consists of a single layer of cuboid-shaped cells.
What Is the Treatment of a Mesothelial Cyst?
Very few case reports talk about the recommended treatment of the mesothelial cyst. However, as it is a non-cancerous mass, asymptomatic cases can be observed with regular ultrasound scans. Surgical excision can be considered if the cyst becomes symptomatic or grows in size eventually. Contents of the cyst can be aspirated under ultrasound guidance for temporary relief, although the fluid reaccumulates. After the surgery, the prognosis is excellent, without any incidence of recurrence.
Conclusion:
A mesothelial cyst is an extremely rare cyst that is lined by mesothelial cells. They are also called the primary retroperitoneal cyst of mesothelial origin. The cyst can occur in adults or children and be asymptomatic in the initial stages. Long-standing lesions might cause chronic abdominal pain. Diagnosing mesothelial cysts only based on clinical findings is quite challenging. They usually do not show any signs or symptoms. The diagnosis is confirmed after the ultrasound, CT, and MRI scans. Asymptomatic cases can be observed with regular ultrasound scans. Surgical excision can be considered if the cyst becomes symptomatic or grows in size eventually. The prognosis after the treatment is excellent, and the cyst does not show recurrence.
