IN SHORT
Mesothelioma is a tumor that originates from a line of cells known as the mesothelial cells. The tumor arises primarily in the pleura but can also arise from the pericardium, peritoneum and scrotal sac. The most common risk factor is asbestos exposure. It can occur in any age group.
What is Mesothelium?
There are different types of cellular arrangement in the body. Mesothelium is the simplest one- realistically called simple squamous cells. (Think of a single layer of flat cells.) This line of cells provides protection in areas where there is continual expansive effort like respiration, heart contraction and dilation.
Where in the body is the mesothelium?
Lungs – Take this scenario where you don’t have the mesothelium to cover your lungs. Now take a deep breath. (Ok I forgot you won’t be able to take a deep breath.) It’s the difference between the atmospheric pressure and pressure within the mesothelium that enables us to inspire and expire properly. Even so, if you were able to inspire somehow, it means that your lungs will be traumatized by the constant friction with the inner surface of the chest wall. So in the case of lungs, the mesothelium forms a sac or cavity (known as the pleural cavity) with a film of liquid to act as a lubricant.
Abdomen – the abdomen also participates in the act of respiration. And so, the abdominal version of the mesothelial sac (known as peritoneal cavity) provides similar function as inthe lungs. Additionally it effectively partitions critical organs from other organs that are commonly diseased. (An example is kidney and appendix.) Ever asked yourself why the abdominal organs don’t fall as we stand? The abdominal mesothelium, through its extension (mesentery), attaches the stomach, intestines and the other organs to the posterior wall of the abdomen.
Scrotal sac – this is extension of the peritoneum during descent of testis, thus similar to abdominal mesothelium.
Heart – similar mechanism provides lubrication during the heart’s contraction and dilation.
But with all its blessings the mesothelium can be a disaster gateway. Since it’s in direct contact with organs, any infiltrative condition in this cell line can happily disperse to all the vital organs. (This is exactly what mesothelioma is.)
Pathology of mesothelioma
Mesothelioma = mesothelium + oma (oma or tumor of the mesothelium)
The genesis of the tumor requires carcinogenic agent(s) with/out genetic susceptibility. (Genetic susceptibility will only exacerbate the condition but won’t be able to cause the disease alone.) For a detailed discussion of these risk factors, check out causes of mesothelioma.
The interaction between the carcinogenic agents and the host mesothelial cells may follow one or more of the following:
- Alter secretory properties of macrophages
- Mediate entry of foreign DNA into the target cells
- Inhibit tumor suppressor genes
- Activate oncogenes
- Activate telomerase
- Prevent apoptosis
Dissemination to other areas may involve the lymphatic channels.
How big is the disease?
Quick Facts -
Mesothelioma occurs more often in men than women (3:1 ratio)
Risk increases with age; malignant mesothelioma occurs in children
Approximately 75 percent of all mesothelioma is pleural
More than 2000 new cases are diagnosed each year
An average death rate of 14.1 per 1,000,000 was reported in the US from 1999 to 2005
What's Next?
Causes of Mesothelioma
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