Mesothelioma is a rare and aggressive cancer that originates from the mesothelial cells that line the serous cavities, such as the pleura, peritoneum, pericardium, and tunica vaginalis.

Mesothelioma is strongly associated with asbestos exposure, which can cause chronic inflammation and DNA damage in the mesothelial cells.

Mesothelioma has a long latency period, ranging from 20 to 50 years, and a poor prognosis, with a median survival of less than one year.

HISTOLOGY OF MESOTHELIOM

Histology is the study of the microscopic structure and function of cells and tissues. Mesothelioma can be classified into three main histological types: epithelioid, sarcomatoid, and biphasic.

1). Epithelioid mesothelioma is the most common and least aggressive type, accounting for 50 - 70% of cases. It is composed of polygonal or cuboidal cells with eosinophilic cytoplasm and round or oval nuclei. The cells can form various patterns, such as tubular, papillary, solid, or microcystic. Epithelioid mesothelioma has the best response to treatment and the longest survival.

2). Sarcomatoid mesothelioma is the least common and most aggressive type, accounting for 10 - 20% of cases. It is composed of spindle-shaped cells with scant cytoplasm and elongated nuclei. The cells can form various patterns, such as fibrous, desmoplastic, or heterologous.

3). Sarcomatoid mesothelioma has the worst response to treatment and the shortest survival.

4). Biphasic mesothelioma is a mixed type, accounting for 20 - 35% of cases. It contains both epithelioid and sarcomatoid components, which can vary in proportion and distribution. Biphasic mesothelioma has an intermediate response to treatment and survival, depending on the ratio of the two components.

PATHOLOGY OF MESOTHELIOMA

Pathology is the study of the causes and effects of diseases. Mesothelioma can affect various organs and systems, causing different symptoms and complications. Some of the common pathological features of mesothelioma are:

1). Pleural effusion, which is the accumulation of fluid in the pleural space, causing shortness of breath, chest pain, and cough.

2). Peritoneal ascites, which is the accumulation of fluid in the peritoneal cavity, causing abdominal distension, pain, and weight loss.

3). Pericardial tamponade, which is the compression of the heart by fluid in the pericardial sac, causing chest pain, palpitations, and low blood pressure.

4). Tumor invasion, which is the spread of the cancer cells to the adjacent or distant organs, such as the lungs, liver, spleen, or lymph nodes, causing organ dysfunction and metastasis.

5). Immunological reactions, which are the responses of the immune system to the cancer cells, such as producing antibodies, cytokines, or autoantigens, causing inflammation, fibrosis, or autoimmune diseases.

SYMPTOMS OF MESOTHELIOMA

Mesothelioma is a rare and aggressive cancer that affects the lining of the internal organs, especially the lungs and the abdomen. It is mainly caused by exposure to asbestos, a mineral that can cause inflammation and DNA damage in the cells. Mesothelioma has a long latency period and a poor prognosis.

Its symptoms include:

i). Chest pain, shortness of breath, cough, and fluid buildup in the chest (pleural mesothelioma).

ii). Abdominal pain, swelling, nausea, weight loss, and fluid buildup in the abdomen (peritoneal mesothelioma).

iii). Heart problems, such as chest pain, irregular heartbeat, and fluid buildup around the heart (pericardial mesothelioma)

These symptoms are not specific to mesothelioma and can be caused by other conditions.

RISK FACTORS for MESOTHELIOMA

1). Asbestos exposure

Between 70% to 80% of people diagnosed with mesothelioma have been exposed to asbestos, usually in the workplace. Asbestos is a group of natural minerals that occur as bundles of tiny fibers. These fibers can be inhaled or swallowed and can damage the cells of the pleura, peritoneum, pericardium, or tunica vaginalis. Asbestos exposure can also increase the risk of lung cancer and other diseases.

2). Smoking

Smoking does not directly cause mesothelioma, but it can increase the risk of lung cancer in people who have been exposed to asbestos. Smoking can also impair the clearance of asbestos fibers from the lungs and worsen the inflammation and scarring caused by asbestos.

3). Radiation exposure

Radiation exposure can increase the risk of mesothelioma, especially in people who have received radiation therapy for lymphoma or other cancers. Radiation can also damage the DNA of the cells and cause mutations that lead to cancer.

4). Genetics

Some people may have a genetic predisposition to develop mesothelioma, such as having a mutation in the BAP1 gene. This gene normally helps protect the cells from DNA damage and tumor formation. People with a family history of mesothelioma may also have a higher risk of developing the disease.

DIAGNOSIS OF MESOTHELIOMA

To diagnose mesothelioma, doctors may use various tests, such as:

i). Physical exam, to check for any lumps or other signs of the disease.

ii). Imaging tests, such as X-rays, CT scan, MRI, or PET scan, to look for abnormalities in the chest or abdomen.

iii). Biopsy, to remove a small sample of tissue or fluid for laboratory examination. This is the only way to confirm the presence of mesothelioma and its type (epithelioid, sarcomatoid, or biphasic).

iv). Staging tests, to determine how far the cancer has spread to other parts of the body. The stages of pleural mesothelioma range from I to IV, with lower stages indicating a more localized disease and higher stages indicating a more advanced disease.

TREATMENT OF MESOTHELIOMA

To treat mesothelioma, doctors may use various options, such as:

i). Surgery, to remove as much of the tumor as possible. This may involve removing part or all of the affected organ, such as the lung, the lining of the chest or abdomen, or the diaphragm.

ii). Radiation therapy, to use high-energy beams to kill cancer cells or shrink tumors. This may be given before or after surgery, or as a palliative treatment to relieve symptoms.

iii). Chemotherapy, to use drugs to kill cancer cells or stop them from growing. This may be given by mouth, injection, or directly into the chest or abdomen. Chemotherapy may be combined with surgery or radiation therapy, or used alone as a palliative treatment.

iv). Immunotherapy, to use drugs that stimulate the immune system to fight cancer cells. This is a newer type of treatment that may be given to people who have advanced or recurrent mesothelioma that does not respond to other treatments.

PROGNOSIS OF MESOTHELIOMA

The prognosis of mesothelioma depends on many factors, such as the type, stage, and location of the cancer, the patient's age, health, and response to treatment, and the availability of clinical trials. Unfortunately, mesothelioma often has a poor prognosis, with a median survival of less than one year. However, some people may live longer than the average, especially if they receive early diagnosis and treatment, or participate in experimental therapies.

STAGES OF MESOTHELIOMA

The stages of mesothelioma indicate how far the cancer has spread in the body. Doctors use different staging systems for different types of mesothelioma. The most common type is pleural mesothelioma, which starts in the lining of the lungs. The staging system for pleural mesothelioma is based on three factors: the size and location of the tumor (T), the involvement of nearby lymph nodes (N), and the presence of distant metastasis (M).

The four stages of pleural mesothelioma are:

• Stage 1: The tumor is confined to the lining of one lung and has not spread to nearby lymph nodes or other organs. This is the earliest and most treatable stage.

• Stage 2: The tumor has grown into the lung tissue or the diaphragm and may have spread to nearby lymph nodes. This stage is still considered localized and may be treated with surgery and other therapies.

• Stage 3: The tumor has invaded the chest wall, the mediastinum (the space between the lungs), or the pericardium (the sac around the heart) and has spread to more distant lymph nodes. This stage is considered advanced and may require more aggressive treatments.

• Stage 4: The tumor has spread to distant organs, such as the liver, the bones, or the brain. This is the most advanced and least treatable stage.

Other types of mesothelioma, such as peritoneal mesothelioma (which starts in the lining of the abdomen) or pericardial mesothelioma (which starts in the lining of the heart), do not have specific staging systems. Doctors may use general terms, such as localized, advanced, or metastatic, to describe the extent of the disease.

The stage of mesothelioma is one of the most important factors that affect the prognosis and treatment options for patients. Generally, the earlier the stage, the better the outcome and the more choices available. However, other factors, such as the type, histology, and location of the cancer, the patient's age, health, and preferences, and the availability of clinical trials, also play a role in determining the best course of action.