Malignant mesothelioma is an aggressive cancer that develops in the mesothelium, a thin layer of tissue covering most internal organs. While it can affect the lining of the abdomen or heart, the most common form impacts the pleura, the tissue surrounding the lungs. This disease is distinct from lung cancer, as it originates in the lining tissue rather than the lung itself. The primary cause of malignant mesothelioma is exposure to asbestos.
The Role of Asbestos Exposure
Asbestos is a group of six naturally occurring fibrous minerals valued for their heat resistance and insulating properties. Exposure happens when microscopic asbestos fibers are inhaled or swallowed, often in occupational settings. These fibers can become permanently lodged in the mesothelium, the protective lining of organs like the lungs and abdomen.
This persistent inflammatory response can cause genetic damage to the mesothelial cells. The asbestos fibers can interfere with normal cell division and generate reactive oxygen species, which are unstable molecules that damage DNA. This process can eventually trigger the malignant transformation of healthy cells into cancerous ones. A distinct characteristic of mesothelioma is its long latency period, as the time between initial asbestos exposure and symptoms can range from 20 to 60 years.
Types and Symptoms of Mesothelioma
Mesothelioma is classified by the location in the body where the cancer originates, with each type presenting unique symptoms. The two most prevalent forms are pleural and peritoneal mesothelioma. Rarer forms can also develop in the linings of the heart and testes.
Pleural Mesothelioma
Pleural mesothelioma, which accounts for approximately 70% to 79% of all cases, develops in the pleura, the tissue lining the lungs and chest wall. As tumors grow, they can exert pressure on the lungs, leading to respiratory symptoms like shortness of breath, a persistent dry cough, and chest pain. Unexplained weight loss and fatigue are also common signs.
Peritoneal Mesothelioma
Peritoneal mesothelioma forms in the peritoneum, the lining of the abdominal cavity, and accounts for about 10% to 30% of diagnoses. Symptoms are related to tumor growth within the abdomen and can include abdominal pain, swelling, and changes in bowel habits like constipation or diarrhea. Individuals may also experience nausea and the formation of lumps in the abdominal area.
Rarer Forms
Less common types include pericardial and testicular mesothelioma. Pericardial mesothelioma develops in the pericardium, the lining surrounding the heart, and can cause chest pains and difficulty breathing. Testicular mesothelioma affects the lining around the testicles and may present as swelling or a mass in a testicle.
The Diagnostic Process
Diagnosing mesothelioma begins with a physical examination and a review of the patient’s medical history. A doctor will inquire about symptoms and any past exposure to asbestos, given its direct causal link to the disease.
Following the initial assessment, imaging tests are ordered to visualize the chest or abdomen. Chest X-rays, CT scans, and PET scans are used to look for signs of mesothelioma. These scans can reveal abnormalities such as fluid buildup, thickening of the mesothelial lining, or the presence of tumors.
While imaging tests can suggest mesothelioma, a biopsy is the only method to confirm the diagnosis. This procedure involves removing a small tissue or fluid sample from the affected area for microscopic examination. A pathologist analyzes the sample to identify malignant mesothelial cells and determine the specific cell type—most commonly epithelioid, sarcomatoid, or biphasic—which helps guide treatment decisions.
Medical Treatment Approaches
Treatment for malignant mesothelioma often involves a combination of therapies, known as multimodal therapy. This approach is tailored to the individual based on the cancer’s stage, location, and overall health. The goal of treatment may be to remove the cancer, control its growth, or relieve symptoms and improve quality of life.
Standard treatment options include surgery, chemotherapy, and radiation therapy. Surgical procedures, such as a pleurectomy/decortication (P/D), aim to remove as much of the visible tumor as possible. Chemotherapy uses drugs to kill cancer cells, while radiation therapy uses high-energy rays to destroy them in a specific area.
In addition to established methods, newer treatments are becoming more common. These can include:
- Immunotherapy, which helps the body’s immune system recognize and fight cancer cells.
- Targeted therapy, which uses drugs that focus on specific abnormalities within cancer cells.
- Palliative care, which focuses on managing symptoms like pain and shortness of breath to enhance comfort.
- Clinical trials, which may provide access to innovative and experimental therapies.