Epithelioid Mesothelioma

Epithelioid mesothelioma, a cancer linked to asbestos exposure, constitutes the majority of mesothelioma cases, ranging from 50% to 70%.

Epithelioid mesothelioma is characterized by the presence of epithelial cells, one of the four primary tissue types in the human body. These cells are naturally found on the skin’s surface, lining hollow organs, blood vessels, and internal cavities. When exposed to asbestos fibers, these epithelial cells can undergo mutations, leading to cancer. Epithelioid mesothelioma is the most prevalent subtype, affecting 50% to 70% of all mesothelioma cases.

Epithelioid cells can exhibit various shapes, including cubed, columnar, and squamous (flat), with squamous cells commonly found in the lining of the lungs (pleura). Notably, epithelioid mesothelioma cells tend to adhere to each other, forming small clusters that may be round or oval, and are characterized by visible nuclei.

Symptoms and Presentation

The presentation of symptoms in malignant epithelioid mesothelioma can be influenced by factors such as the cancer’s location, the patient’s general health, age, and the stage of the disease. Severe symptoms may not manifest until the disease has advanced. Typical signs encompass chest discomfort, coughing, hoarseness, breathing difficulties (dyspnea), elevated body temperature, and the accumulation of fluid in the lung cavity (pleural effusion). In cases of peritoneal mesothelioma, patients may experience symptoms like abdominal pain, enlargement, constipation, fever, the buildup of fluid in the abdominal cavity (peritoneal effusion), and loss of body weight.

Diagnosis and Confirmatory Tests

The diagnostic process for epithelioid mesothelioma typically begins with a series of imaging tests, including X-rays, CT scans, PET scans, or MRIs. In cases where a tumor or abnormality is detected, a blood test may be ordered to identify specific biomarkers associated with mesothelioma. Confirmatory diagnosis is achieved through a biopsy, which can be either non-surgical or surgical, involving the removal of a tissue sample for analysis. Immunohistochemistry (IHC) is a recommended method for confirming the diagnosis, as it can differentiate mesothelioma from other cancers such as adenocarcinoma.

Rare Epithelial Cell Types

In addition to the common epithelioid subtype, several rare variants have been identified:

• Adenomatoid Mesothelioma: Forms in glandular structures and may be benign or malignant.
• Adenoid Cystic Mesothelioma: A rare subtype found in the peritoneal or pleural cavities, more commonly diagnosed in young women.
• Deciduoid Mesothelioma: Typically develops in the abdomen or lung lining and is most often diagnosed in women.
• Small Cell Mesothelioma: Sometimes confused with small cell lung cancer, it forms in the peritoneum and pleura.
• Well-Differentiated Papillary Mesothelioma (WDPM): Typically seen in the pleura, peritoneum, and genitals, characterized by slow metastasis.

Prognosis for Epithelioid Mesothelioma

Prognosis for epithelioid mesothelioma varies based on multiple factors, including cell type, cancer stage, patient age, overall health, and pre-existing conditions. Patients with epithelioid mesothelioma generally have a more favorable prognosis, with survival spanning from 1.5 to 6.5 years. A study comparing survival rates in pleural mesothelioma patients treated with multimodal therapy highlights the following median survivals:

• Epithelial mesothelioma: ~23 months
• Biphasic mesothelioma: ~14 months
• Sarcomatoid mesothelioma: ~11 months

The prognosis is also influenced by the cancer’s location and staging, as well as the patient’s age and overall health.

Treatment Options for Epithelioid Mesothelioma

Treatment strategies for epithelioid mesothelioma encompass surgery, chemotherapy, radiation therapy, immunotherapy, and various combinations of these approaches. Surgery options may include pleurectomy/decortication (P/D) or extrapleural pneumonectomy (EPP), with studies indicating longer survival for epithelial tumors. Immunotherapy, particularly immune checkpoint inhibitors, has become a standard treatment. Chemotherapy, whether systemic or local, is commonly administered, and the addition of Avastin® (bevacizumab) has shown promising results.

Radiation therapy is considered in conjunction with other treatments for pleural mesothelioma. Emerging treatments, such as pressurized chemotherapy (PIPAC), gene therapy, and photodynamic therapy, offer potential avenues for exploration.