Straight Talk about Mesothelioma, a blog series created by Michael T. Milano, M.D., Ph.D., a radiation oncology specialist, as a resource for mesothelioma patients and their loved ones.
Mesothelial Cells in Pleural Fluid
There are certain cells that line the pleura — the thin, double-layered lining which covers the lungs, chest wall, and diaphragm — which are known as mesothelial cells. Other than the pleura, mesothelial cells also form a lining around the heart (pericardium) and the internal surface of the abdomen (peritoneum).
When mesothelial cells are examined under the microscope, they often appear like squamous cells. It is important to note that mesothelial cells have a structure (what doctors call “morphology”) like squamous cells, but in reality, they are a unique type of epithelial cell.
What Role Does Cell Type Play in a Cancer Diagnosis?
There are many different kinds of cells in the human body, and each different kind serves a specific function. Some estimates say that there are up to 200 trillion cells inside of a human body. Almost every single organ inside the body is covered by a lining of cells, and these cells are known by scientists and doctors as epithelial cells.
Whenever a doctor suspects cancer in a patient, he or she will nearly always perform a biopsy to determine the cell type. The tissue is then examined under a microscope. In most cases, the tissues have to be stained so that the internal organs and cell surface can be visualized.
This branch of medicine, known as “histology,” provides the details of the cells, including how developed they are, if they’ve undergone any abnormal changes, and their general growth pattern. When cancerous tissue is examined specifically, this branch of medicine is known as histopathology — and doctors will look exclusively for the presence of abnormal cells.
What Is the Function of Mesothelial Cells?
Mesothelial cells are specialized and have several specific functions:
- They secrete a fluid that lubricates the lungs and allows them to glide over the pleura during breathing. This fluid has a detergent-like effect that creates a “slippery” surface. This enables the lungs to glide in the chest cavity with ease.
- They reabsorb any excess fluid in the chest cavity to prevent fluid accumulation. Normally there is only about half a cup of fluid (about 30-50 cc of fluid) in the pleural lining and this fluid is constantly removed and replaced with fresh fluid. If the mesothelial cells fail to function, the fluid can quickly accumulate, leading to an unhealthy fluid collection in the chest cavity (also known as a “pleural effusion”). As the fluid builds up in the chest cavity, the patient can develop vague chest pain and shortness of breath. These are the two symptoms that are most commonly associated with mesothelioma.
- They are also non-adhesive. To doctors, “non-adhesive” simply means that the cells will not allow the lungs to “stick” to the chest wall or the pleura. This is important because when the lungs inflate and deflate every time a person breathes, it is vitally important that the lungs not get “stuck” to the chest cavity. In such rare cases when the lungs do get “stuck,” breathing becomes labored and serious health issues could result.
- Arguably, one of the mesothelial cells’ largest roles is to protect and prevent organisms like bacteria, viruses, and other foreign particles from entering into the chest cavity. Mesothelial cells completely surround the bacteria and destroy them.
What Role Do Mesothelial Cells Play During Infection or Injury?
The mesothelial fluid plays a role in repairing damage inside pleural space — the fluid helps transport the body’s defense cells (white cells) to and from sites of infection and inflammation and also helps clean up any areas of congestion.
If for any reason, there is trauma or an infection to the mesothelial lining, this triggers the nearby mesothelial cells to multiply and fight off the infection while at the same time repairing any damages or gaps in the pleural lining. When the healing of the pleural lining is impaired, then the lung can become “trapped” or it can get stuck in the chest cavity. This can halt the normal movements of the lung and interfere with a person’s breathing.
In the case of mesothelioma, when the mesothelial cells are exposed to asbestos fibers, the cells ingest these fibers and prevent them from causing harm. However, if the asbestos exposure is continued over time, such heavy volumes of asbestos can overwhelm the mesothelial cells.
Continued exposure to asbestos fibers damages the mesothelial cells and over time leads to the development of cancer, which can take up to 20-50 years to present.