Mesothelioma: Everything You Need to Know
Mesothelioma is a type of tumor that develops due to the transformation of the mesothelial cells that make up the pleura and peritoneum. Mesothelial cells are composed of two layers: one that surrounds the internal organs and another that lines the lungs and chest cavity. Although less common, the tumor can also develop in the pericardium and tunica vaginalis.
In general, mesothelioma is an aggressive form of cancer with a life expectancy of around 12 months after diagnosis. Currently there are therapies to deal with it, but not all patients respond favorably. We’re going to review everything you need to know about it according to the scientists.
Features of mesothelioma
There are two types of mesothelioma: benign and malignant. Benign mesotheliomas are very rare, and are most common in women between the ages of 20 and 40. The term benign can be misleading, since many of the cases show a high propensity for local recurrence, and, in some contexts, they can evolve into malignant episodes. The most common subtype is benign multicystic mesothelioma of the peritoneum (BMPM).
As the experts indicate, this subtype affects 0.15 people per 100,000 inhabitants per year. Since it was first described in 1979, only around 150 cases have been scientifically analyzed. The subtype can appear in the peritoneum, uterus, rectum, round ligament, small intestine, spleen, liver, kidney, or appendix. It has been linked to episodes of endometriosis and pelvic inflammatory disease.
Benign mesotheliomas are more common than malignant ones, and are mostly related to asbestos exposure (as we’ll see shortly). The first case was reported in 1947 and since then the evidence indicates that up to 70% of the episodes correspond to the malignant pleural mesothelioma subtype. It’s more common in men, with an average age at diagnosis of 72 years.
The malignant tumor usually has a multifocal development and manifests multiple nodules that start in the parietal pleura. From here it spreads to the visceral pleura, chest wall, diaphragm, and mediastinum. The prognosis of life after diagnosis is around 12 months. It’s more common in countries with limited regulations regarding asbestos. An estimated 2,500 cases occur each year in the US.
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Causes and risk factors for the development of mesothelioma
The main cause of the development of mesothelioma is exposure to asbestos. Asbestos refers to a family of six mineral fibers that were used commercially during the second half of the 20th century. Most of them are described only as asbestos, and they were widely used due to their high resistance to fire (especially in the US and Europe).
The association between exposure to asbestos and the development of this type of cancer isn’t recent. As early as 1960, cases were reported with a clear and direct relationship between mineral fiber and disease. As researchers remind us, most of the fibers that make up asbestos are amphibole (that is, sharp) or serpentine. When these are inhaled, they become trapped in the lower third of the lung, at which point they generate an inflammatory response.
The fibers are known to be engulfed in mesothelial cells. In doing so, they trigger a wave of oncogenic events, such as activation of the c-Myc and c-Jun oncogenes, binding to epidermal growth factor receptors (EGFR) and the promotion of antiapoptotic genes such as Bcl-xl. The average exposure to asbestos for the development of this type of cancer ranges from 20 to 50 years.
Although between 70% and 80% of the cases correspond to some degree of exposure to asbestos, not all episodes are explained by this route. For example, benign mesothelioma doesn’t seem to be related to it. Exposure to the Simian 40 virus, genetic predisposition, trauma and mechanical injury, and interaction with other fibers may also be behind it. Regarding the latter, it has been suggested that carbon nanotubes in some household appliances generate similar responses.
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The symptoms of this type of cancer aren’t manifest during the initial phases. Even through specialized tests, such as X-rays, there may be no overt indication of an abnormality. In general, the signs of mesothelioma vary according to the location, type, and stage of the cancer. We review some of the main ones:
- Difficulty breathing
- Pain in the chest, lower back, or abdomen
- Difficulty swallowing
- Chronic cough
- Pleural effusion
- Unexplained weight loss
- Swelling in the extremities or face
- Nausea and vomiting
- Diarrhea and constipation
- Loss of appetite
- Small bowel obstruction
- Low blood pressure
- Heart palpitations
Many of these symptoms can overlap with pulmonary fibrosis, pulmonary embolism, pneumonia, lung infections, and other complications. The tumor is only detected when the symptoms are very evident and the subject seeks medical attention. A chest radiography, CT scan, ultrasound-guided needle aspiration, and biopsy are helpful in the diagnostic process.
Mesothelioma is characterized as an aggressive cancer, with a life expectancy of one year after diagnosis. Available options vary according to the site, extent, age, general health of the patient, and degree of malignancy. Standard therapy revolves around the surgical removal of all or part of the tumor and affected tissues.
Radiation therapy, chemotherapy, immunotherapy, gene therapy, and targeted therapy may also be considered. The roadmap will be chosen by the specialist in an interview with the patient. Palliative care is essential regardless of the prognosis, all this to prevent symptoms from worsening and to counteract their emotional effects. For this reason, doctors choose to approach the treatment in a personalized way.It might interest you...
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