Mesothelioma

Mesothelioma is a type of cancer originating from the thin layer of tissue covering many internal organs, known as the mesothelium. The most commonly affected area is the lining of the lungs and chest wall, but it can also affect the abdomen, heart, and testes. Mesothelioma is heavily associated with asbestos exposure, with symptoms typically manifesting 20 to 50 years post-exposure.

Signs and Symptoms

Lungs

Symptoms of pleural mesothelioma include chest wall pain, pleural effusion (fluid surrounding the lung), shortness of breath, fatigue, wheezing, hoarseness, cough, and hemoptysis (blood in sputum). In severe cases, patients may present with multiple tumour masses and pneumothorax (collapsed lung).

Abdomen

Peritoneal mesothelioma symptoms include abdominal swelling and pain due to ascites (fluid buildup), weight loss, fever, night sweats, poor appetite, vomiting, constipation, and umbilical hernia. Late-stage symptoms may involve difficulty swallowing and swelling of the neck or face.

Heart

Pericardial mesothelioma can present with constrictive pericarditis, heart failure, pulmonary embolism, and cardiac tamponade. Other symptoms include substernal chest pain, orthopnea (difficulty breathing when lying flat), and cough due to the tumour encasing or infiltrating the heart.

End-stage

In severe cases, signs and symptoms may include blood clots in veins (thrombophlebitis), disseminated intravascular coagulation (severe bleeding), jaundice, low blood sugar, pleural effusion, pulmonary embolism, and severe ascites.

Causes

Asbestos

Asbestos exposure is the primary risk factor for mesothelioma, with high incidence in populations near naturally occurring asbestos or in those involved in mining, producing, or working with asbestos products. Other risk factors include genetic predispositions and exposure to erionite, a zeolite mineral. Pericardial mesothelioma may not always be linked to asbestos exposure.

Pathophysiology

Mesothelioma development involves asbestos fibres penetrating lung tissue and reaching the pleural surface. This leads to the formation of malignant mesothelial plaques. The fibres can also be transported to the abdomen via the lymphatic system. Asbestos acts as a complete carcinogen, with direct physical interactions with mesothelial cells and indirect effects through inflammatory responses.

Diagnosis

Imaging

Mesothelioma diagnosis relies on imaging techniques such as chest X-rays, CT scans, and MRIs. These can reveal pleural thickening and fluid buildup, indicative of mesothelioma. Advanced imaging may be required for further evaluation.

Biopsy

A definitive diagnosis is made through a biopsy, where tissue samples are examined under a microscope. Techniques include thoracoscopy, thoracotomy, and laparoscopy, depending on the tumour's location.

Immunochemistry

Immunohistochemical tests help differentiate mesothelioma from other cancers, using markers such as calretinin and WT1.

Treatment

Surgery

Surgery options include pleurectomy/decortication, removing the chest lining, and extrapleural pneumonectomy, removing the lung, chest lining, diaphragm, and pericardium. Complete tumour removal is often not possible.

Radiation

Radiation therapy can be used post-surgery to treat the hemithorax or as palliative care to relieve symptoms. Its efficacy varies and can induce severe side effects.

Chemotherapy

Chemotherapy has shown to improve survival in mesothelioma patients. The combination of cisplatin and pemetrexed is effective, with vitamin supplementation reducing side effects.

Immunotherapy

Recent advancements include the FDA approval of nivolumab and ipilimumab for unresectable malignant pleural mesothelioma, showing improved survival rates.

Prognosis

Mesothelioma generally has a poor prognosis, with typical survival between 12 and 21 months post-diagnosis. Prognosis is better in women, younger individuals, and those with epithelioid histology. Negative prognostic factors include sarcomatoid histology and high platelet counts.

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Self-assessment MCQs (single best answer)

Which area is most commonly affected by mesothelioma?

What is the primary risk factor for developing mesothelioma?

Which of the following is NOT a symptom of pleural mesothelioma?

What imaging technique is commonly used to reveal pleural thickening and fluid buildup indicative of mesothelioma?

What biopsy technique is used to diagnose mesothelioma in the chest area?

Which marker is used in immunohistochemical tests to help differentiate mesothelioma from other cancers?

Which combination of chemotherapy drugs has shown effectiveness in treating mesothelioma?

Which of the following is a recent advancement in mesothelioma treatment that has shown improved survival rates?

Which type of mesothelioma is associated with symptoms like abdominal swelling and pain due to ascites?

Which of the following is NOT considered a negative prognostic factor in mesothelioma?