Mesothelioma is a type of cancer which develops from the layers of tissue that covers the outer surface of body organs specially, the lung (the pleura).
The other organs that it can rarely affect includes tummy lining (peritoneal mesothelioma), heart and testicles.
Mesothelioma is invariably associated with exposure to asbestos.
More than 80% of mesothelioma cases are caused by exposure to asbestos.
Asbestosis is a group of minerals made of microscopic fibres that used to be widely used in construction. These asbestosis can easily get into the lung tissue and stuck there damaging the lung and eventually leading to cancer.
Patient usually develops mesothelioma after more than 20 years of exposure.
Other risk factors includes:
infection with the simian virus 40.
The mesothelium consists of a single layer of flattened to cuboidal cells forming the epithelial lining of the serous cavities of the body including the peritoneal, pericardial and pleural cavities.
Deposition of asbestos fibers in the parenchyma of the lung may result in the penetration of the visceral pleura from where the fiber can then be carried to the pleural surface, thus leading to the development of malignant mesothelial plaques. The processes leading to the development of peritoneal mesothelioma remain unresolved, although it has been proposed that asbestos fibers from the lung are transported to the abdomen and associated organs via the lymphatic system. Additionally, asbestos fibers may be deposited in the gut after ingestion of sputum contaminated with asbestos fibers
TYPES OF MESOTHELIOMA
There are three main histological subtypes of malignant mesothelioma:
- Epithelioid: Epithelioid mesothelioma is characterized by high levels of calretinin.
- Sarcomatous: Sarcomatous mesothelioma does not express high levels of calretinin.
Other morphological subtypes have been described:
- Clear cell
- Cartilaginous and osseous metaplasia
Mesothelioma does not have many symptoms initially but as they grow and starts pressing on a nerve or another body organ, then patient starts to develop symptoms.
The symptoms can vary according to the site:
The following are different symptoms if mesothelioma affects pleura:
- chest pain
- tiredness (fatigue)
- raised temperatures
- a persistent cough
- loss of weight
- loss of appetite
- difficulty swallowing
- a hoarse or husky voice
The patient of mesothelioma involving peritoneum may present with the following symptoms:
- pain in the tummy (abdomen)
- swelling in the abdomen
- feeling or being sick
- poor appetite
- losing weight when not dieting
- diarrhoea or constipation
End stage or advanced mesothelioma
As the disease progresses there may be multi system involvement which can present with the followings:
- Blood clots in the veins, which may cause thrombophlebitis
- Disseminated intravascular coagulation, a disorder causing severe bleeding in many body organs
- Jaundice, or yellowing of the eyes and skin
- Low blood sugar level
- Pleural effusion
- Pulmonary emboli, or blood clots in the arteries of the lungs
- Ascites: severe
- changes in the shape of their fingers and nails (called finger clubbing)
The most common sites for metastases includes the liver, adrenal gland, kidney, or other lung.
- Metastatic adenocarcinoma
- Pleural sarcoma
- Synovial sarcoma
- Metastatic clear cell renal cell carcinoma
- Metastatic osteosarcoma
If a person presents with the above symptoms and is particularly have a history of exposure to asbestos
in the past, a clinical suspicion about mesothelioma must be made.
A number of different tests may help to diagnose mesothelioma and show how far it has spread. These tests includes:
- An X-ray of your chest or tummy
- A computerised tomography (CT) scan – a number of X-ray images are taken to create a detailed image of the inside of the body
- Confirmatory tests are either examining fluid produced by the cancer or by a tissue biopsy of the cancer. These includes:
- fluid drainage – if there’s a build-up of fluid around the lungs or in the tummy, a sample may be removed using a needle inserted through the skin so the fluid can be analysed.
- a thoracoscopy or laparoscopy – the inside of your chest or tummy is examined with a long, thin camera that’s inserted through a small cut (incision) under sedation or anaesthetic; a sample of tissue (biopsy) may be removed so it can be analysed
There are different treatment options available but the appropriate treatment is decided based on patient and disease factor. The following are different range of options:
- chemotherapy – main treatment for mesothelioma and involves using medicine to help shrink the cancer
- radiotherapy – this involves using high-energy radiation to kill cancer cells and it may be used to slow the cancer down and keep it under control
- surgery – an operation to remove the cancerous area can be done if mesothelioma is detected at a very early stage, although it’s not clear whether surgery is helpful
- Pleurodesis: It is a procedure which involves using substances such as talc to scar together the pleura, may be used to prevent more fluid from building up around the lungs
Newer options of treatments are:
-intrapleural inoculation of Bacillus Calmette-Guérin (BCG) to boost the immune response
-in vitro lysis by LAK cells following activation by interleukin-2 (IL-2) but has major side effects (trial suspended)
- Heated intraoperative intraperitoneal chemotherapy
This technique is used in conjunction with surgery. The surgeon removes as much of the tumor as possible followed by the direct administration of a chemotherapy agent,
heated to between 40 and 48 °C, in the abdomen. The fluid is perfused for 60 to 120 minutes and then drained. High concentrations of selected drugs are then administered into the abdominal and pelvic surfaces. Heating the chemotherapy treatment increases the penetration of the drugs into tissues. Also, heating itself damages the malignant cells more than the normal cells
Unfortunately, mesothelioma is often diagnosed at an advanced stage, treatment is usually focused on controlling the symptoms and prolonging life for as long as possible. This is known as palliative or supportive care.
The prognosis for mesothelioma tends to be poor. This is because it is usually diagnosed in advanced stages when it becomes symptomatic. It is unfortunate that it can progress quite quickly once it reaches this stage.
Typical survival despite surgery is between 12 and 21 months depending on the stage of disease at diagnosis with about 7.5% of people surviving for 5 years
- around half (50%) of people with mesothelioma will live at least a year after diagnosis
- around one in every 10 people (10%) with mesothelioma will live at least five years after diagnosis