Mesothelial hyperplasia and proliferation occur when unusual cell growth occurs in the mesothelium. While it is not malignant, mesothelial hyperplasia may later become cancerous. An accurate diagnosis is important for timely and proper treatment and to avoid a benign proliferation developing into a malignancy.
What Is Mesothelial Hyperplasia?
Mesothelial hyperplasia, also known as mesothelial proliferation, is an increase in the number of cells in the mesothelium. A proliferation of cells in tissues that don’t usually grow and divide rapidly is not necessarily an indication of cancer.
Hyperplasia may become cancer, but there may be other non-malignant causes.[1] Simple tissue irritation can cause cells to proliferate and produce benign tumors, for instance.
It is sometimes called reactive mesothelial hyperplasia because it often occurs in reaction to something: an injury or infection, for instance.
Is Mesothelial Hyperplasia a Cancer?
The overgrowth and proliferation of mesothelial cells is not itself a cancer. It might indicate that a patient has cancer, and it could develop into cancer later. Hyperplasia is more likely to be a sign of cancer if a patient has past asbestos exposure.
Mesothelial Hyperplasia vs. Mesothelioma
Mesothelial hyperplasia and mesothelioma are not the same. Hyperplasia is often benign, while mesothelioma is malignant. Hyperplasia in the mesothelium can be malignant and develop into mesothelioma.
Asbestos and Mesothelial Hyperplasia
Asbestos exposure has been connected to mesothelial hyperplasia and is a known cause.[2] Fibers of asbestos lodged in tissues in the body trigger inflammation and can lead to a proliferation of cells.
This may be benign or ultimately malignant, but asbestos exposure is a strong risk factor for mesothelioma.
What Causes Benign Mesothelial Proliferation?
While reasons for mesothelial hyperplasia are not always clear, there are several potential causes:[3]
- This condition can be caused by an infection or may be a reaction to certain drugs.
- Hyperplasia may be a symptom of a collagen vascular disease or a result of surgery, trauma, or physical injury.
- A collapsed lung can also lead to mesothelial proliferation.
- Hyperplasia may also occur in the cells of the mesothelium in the abdomen, known as the peritoneum. It can result from infection, inflammation, ovarian abscesses, or a buildup of fluid in this area.
Diagnosing Mesothelial Hyperplasia
Physicians can detect hyperplasia by examining biopsy samples under a microscope. A doctor may order a biopsy based on symptoms and imaging scans.
A medical professional will insert a long, thin needle into the chest cavity to remove a piece of pleural tissue or into the abdomen for tissue from the peritoneum to extract an adequate sample. Once the sample has been extracted, a pathologist will examine it to determine if there is a proliferation of the mesothelial cells.
Hyperplasia can be detected when normally elongated mesothelial cells appear more cubical but otherwise look normal.
If those cells look unusual in any way, whether they are abnormally large or are projecting into other areas of tissue, it could be atypical mesothelial hyperplasia.[3]
Atypical proliferation does not necessarily signify malignancy. More tests are necessary to rule out mesothelioma. Ongoing diagnosis may involve blood tests to look for markers indicative of cancer, and ongoing testing of biopsy samples will be needed to look for abnormal or cancerous cells.
Sometimes it is difficult to determine if the proliferation is malignant. In many cases, doctors diagnose atypical mesothelial hyperplasia and then continue testing for signs of malignancy.[4]
Invasion Helps Distinguish Malignancy from Hyperplasia
While it is difficult for pathologists to determine if a proliferation of mesothelial cells is benign or malignant, recent research shows that invasion of the cells is a key factor that may indicate cancer.
When hyperplasia can be seen invading other tissues in biopsy samples, this is a strong indication the growth is malignant.[4]
In the case of the mesothelium, when the cells invade fat tissue near the pleura, it is more likely to be mesothelioma than benign hyperplasia.
The cells may also invade lung tissue, muscle tissue, or other organ tissues to be considered malignant; however, fat is the most common tissue invaded by these cells.
Treating Mesothelial Hyperplasia
If doctors are confident that mesothelial proliferation is benign, a patient may need no treatment. When treatment is necessary, it should address the underlying cause of the proliferation, although this is often difficult to determine.
If an infection or injury is responsible for the growth, treatment for those conditions should reduce proliferation. If doctors cannot determine a cause, treatment only proceeds if the growth is causing discomfort. Surgery is risky and usually only done if the growth can be easily removed, providing relief for the patient.
It is also important to consider the possibility of an incorrect diagnosis. Because it is so difficult to distinguish between benign and malignant growths, mistakes are often made. Patients should not hesitate to request ongoing screenings to check the progress of the hyperplasia. Regular screenings can track growth and catch signs of malignancy as early as possible.
