What Is Pleural Mesothelioma?

Understanding Pleural Mesothelioma

Pleural mesothelioma is a malignant cancer that develops in the pleura — the thin, two-layered membrane that surrounds the lungs and lines the inside of the chest wall. It is the most common type of mesothelioma, accounting for roughly 75% of all diagnosed cases, according to the American Cancer Society.

The pleura consists of two layers: the visceral pleura, which covers the lungs, and the parietal pleura, which lines the chest cavity. Between these layers is a small amount of fluid that allows the lungs to expand and contract smoothly during breathing. When mesothelioma develops in this tissue, tumor growth disrupts this mechanism and leads to progressive breathing difficulty.

How Asbestos Causes Pleural Mesothelioma

Pleural mesothelioma is caused by inhaling microscopic asbestos fibers. When breathed in, these sharp, durable fibers travel deep into the lungs and can penetrate through to the pleural lining. Once embedded in the pleural tissue, the fibers cause chronic inflammation and cellular damage over many years.

The latency period — the time between initial asbestos exposure and a mesothelioma diagnosis — is typically 20 to 50 years. This long delay is one reason why mesothelioma is most commonly diagnosed in people over 65, even though their asbestos exposure occurred decades earlier during their working years.

Occupational exposure remains the leading cause. Workers in construction, shipbuilding, power plants, oil refineries, and industrial manufacturing faced the highest risk, particularly those who worked with asbestos insulation, pipe-fitting materials, brake pads, and fireproofing products.

Symptoms of Pleural Mesothelioma

Symptoms of pleural mesothelioma develop gradually and often mimic less serious respiratory conditions, which can delay diagnosis. Common symptoms include:

Chest pain. A persistent, dull ache in the chest or lower back is one of the earliest and most common symptoms. The pain may worsen with deep breathing or coughing.

Pleural effusion. A buildup of excess fluid between the pleural layers is present in most patients at diagnosis. This fluid accumulation compresses the lung and causes increasing shortness of breath.

Persistent cough. A dry, nonproductive cough that does not respond to standard treatments may indicate pleural involvement.

Dyspnea (difficulty breathing). Progressive breathlessness during normal activities is a hallmark symptom, caused by both tumor growth and fluid accumulation restricting lung expansion.

Additional symptoms may include unexplained weight loss, fatigue, night sweats, and difficulty swallowing. If you have a history of asbestos exposure and experience any of these symptoms of mesothelioma, seek medical evaluation promptly.

Diagnosis and Staging

Diagnosing pleural mesothelioma typically involves imaging studies followed by tissue biopsy. According to the National Cancer Institute, the diagnostic process usually includes chest X-rays and CT scans to identify pleural thickening or fluid, PET scans to assess the extent of disease, and ultimately a biopsy to confirm the diagnosis.

The most definitive diagnostic method is a thoracoscopy, in which a surgeon inserts a small camera into the chest cavity to directly visualize the pleura and obtain tissue samples. Immunohistochemistry testing on the biopsy tissue distinguishes mesothelioma from other cancers, including lung cancer.

Pleural mesothelioma is staged from I to IV using the TNM (Tumor, Node, Metastasis) system. Stage I indicates cancer confined to the pleura on one side of the chest, offering the most treatment options. Stage II involves spread to the lung or diaphragm on the same side. Stage III indicates involvement of nearby lymph nodes or chest wall structures. Stage IV means the cancer has spread to distant organs.

Treatment Options

Treatment for pleural mesothelioma depends on the stage at diagnosis, the cell type, and the patient's overall health. The most effective approach is typically multimodal therapy, which combines two or more treatments.

Surgery. Two primary surgical options exist. Extrapleural pneumonectomy (EPP) removes the affected lung, the surrounding pleura, portions of the diaphragm, and the pericardium. Pleurectomy/decortication (P/D) removes the diseased pleural lining while preserving the lung. P/D has become more widely favored due to lower complication rates and comparable survival outcomes in many cases.

Chemotherapy. The standard first-line chemotherapy regimen is pemetrexed (Alimta) combined with cisplatin or carboplatin. This combination has been shown to improve survival and quality of life compared to single-agent treatment. Chemotherapy may be given before surgery (neoadjuvant) to shrink tumors, or after surgery (adjuvant) to kill remaining cancer cells.

Radiation therapy. Intensity-modulated radiation therapy (IMRT) can target tumors precisely while minimizing damage to surrounding healthy tissue. Radiation is most commonly used after surgery to reduce the risk of recurrence, or as a palliative measure to relieve chest pain and breathing difficulty.

Immunotherapy. In 2020, the FDA approved the combination of nivolumab (Opdivo) and ipilimumab (Yervoy) for unresectable pleural mesothelioma. This immunotherapy treatment has shown meaningful survival benefits for patients who are not surgical candidates.

Prognosis by Stage

Prognosis for pleural mesothelioma varies significantly based on the stage at diagnosis, cell type, and treatment approach. Patients diagnosed at earlier stages who are eligible for multimodal treatment generally have better outcomes.

Epithelioid cell type, which accounts for about 60–70% of pleural mesothelioma cases, carries a more favorable prognosis than sarcomatoid or biphasic types. Patients with Stage I or II epithelioid mesothelioma who undergo aggressive multimodal treatment may achieve median survival times of 2 to 4 years or longer.

Ongoing clinical trials continue to explore new treatment combinations that may extend survival further. Advances in immunotherapy, targeted therapy, and gene therapy represent promising avenues for improving outcomes for pleural mesothelioma patients.