Epithelioid malignant mesothelioma is a rare and aggressive cancer that develops in the thin lining of various internal organs. This article aims to provide a clear overview of epithelioid malignant mesothelioma, covering its definition, causes, symptoms, diagnostic procedures, and current treatment approaches.
What Epithelioid Malignant Mesothelioma Is
Epithelioid malignant mesothelioma is the most frequently observed histological subtype of malignant mesothelioma, making up approximately 50-70% of all cases. This cancer originates from mesothelial cells, which form the mesothelium, the protective lining around organs such as the lungs (pleura), abdomen (peritoneum), heart (pericardium), and testes (tunica vaginalis). The name “epithelioid” refers to the cancerous cells’ resemblance to normal epithelial cells under a microscope. These cells are typically cuboidal, columnar, or flattened, often forming gland-like structures or solid clusters.
Epithelioid cells tend to clump together; while they may divide at a faster rate, their tendency to adhere to one another can reduce the speed at which they metastasize. This characteristic often contributes to a more favorable prognosis for individuals with the epithelioid subtype compared to other mesothelioma cell types.
Understanding Causes and Risk Factors
The primary cause of epithelioid malignant mesothelioma is exposure to asbestos fibers. When these microscopic fibers are inhaled or ingested, they can become lodged in the mesothelium, leading to chronic irritation and cellular damage over time. This irritation can cause healthy mesothelial cells to mutate and become cancerous.
The disease has a long latency period, the time between initial asbestos exposure and symptom appearance or diagnosis. This period commonly ranges from 20 to 60 years, though it can occasionally be shorter, even under 10 years, or extend beyond 70 years. The duration and intensity of asbestos exposure can influence this latency period, with heavier or longer exposures potentially leading to an earlier onset of the disease. While asbestos is the dominant cause, other less common factors like ionizing radiation and mutations in the BRCA1 Associated Protein (BAP1) have also been linked to mesothelioma development.
Recognizing Symptoms and Diagnostic Steps
Symptoms often appear decades after asbestos exposure and can be non-specific, making early detection challenging. The specific symptoms depend on the tumor’s location. For pleural mesothelioma, affecting the lung lining, common symptoms include shortness of breath, chest pain, persistent cough, fluid buildup around the lungs (pleural effusion), difficulty swallowing, arm or face swelling, fatigue, and unexplained weight loss.
If the cancer develops in the abdominal lining (peritoneal mesothelioma), symptoms often include abdominal pain or swelling, fluid buildup in the abdomen (ascites), changes in bowel habits like constipation or diarrhea, nausea, vomiting, and loss of appetite. Fever and night sweats can also occur with both forms. Due to the vague nature of these symptoms, diagnosis can be delayed, with patients often presenting when the disease has already spread within the affected cavity.
The diagnostic process begins with a thorough medical history, including questions about past asbestos exposure, and a physical examination. Imaging tests are then performed to identify abnormalities or tumors, including X-rays, computed tomography (CT) scans, magnetic resonance imaging (MRI), and positron emission tomography (PET) scans. While imaging can suggest mesothelioma, a definitive diagnosis relies on a biopsy. This sample is then examined by a pathologist to confirm cancer cells and determine the specific cell type, often using immunohistochemistry to differentiate it from other cancers like adenocarcinoma.
Current Treatment Options and Prognosis
Treatment for epithelioid malignant mesothelioma often involves a multimodal approach, combining two or more therapeutic methods tailored to the individual patient. Surgical options for pleural mesothelioma include pleurectomy/decortication (P/D), which removes cancerous tissue from the lung lining while preserving the lung, and extrapleural pneumonectomy (EPP), a more extensive procedure involving the removal of the affected lung, pleura, diaphragm, and pericardium. For peritoneal mesothelioma, cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (HIPEC) is a common approach, where tumors are surgically removed, followed by the direct application of heated chemotherapy drugs to the abdominal cavity. Surgery is generally considered for patients with early-stage disease, particularly when the cancer is limited to the lining and has not spread to lymph nodes.
Chemotherapy is a systemic treatment that uses drugs to kill cancer cells or inhibit their growth throughout the body. It is often administered intravenously and can be used before surgery to shrink tumors or after surgery to eliminate remaining microscopic cancer cells.
Radiation therapy uses high-energy beams to target and destroy cancer cells in specific areas. This is typically used after surgery to address any cancer cells that may not have been visibly removed.
Newer targeted therapies and immunotherapies are also emerging. These work by either targeting specific molecules involved in cancer growth or by enhancing the body’s own immune response against cancer cells. For instance, combinations of immunotherapy drugs like nivolumab and ipilimumab, or pembrolizumab with platinum-based chemotherapy, have shown promising results, particularly for patients who are not candidates for surgery.
The prognosis for epithelioid malignant mesothelioma varies considerably, influenced by factors such as the cancer’s stage, its location, the patient’s overall health, and their response to treatment. Generally, patients with the epithelioid subtype tend to have a more favorable outlook compared to those with sarcomatoid or biphasic cell types, as epithelioid cells often respond better to treatment and spread more slowly. While survival statistics vary, studies indicate that patients undergoing multimodal treatments, especially those involving surgery combined with heated chemotherapy, may experience extended survival times. Ongoing research continues to explore new therapies and improve existing ones, contributing to advancements in the management and outlook for individuals with this disease.