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The mesothelium is a membrane of specialized cells that forms the lining of several body cavities, including the chest, abdomen, and pelvis. When these specialized cells propagate and grow in irregular ways, it can be difficult to determine if the growth is benign or malignant. It has always been challenging for doctors to distinguish between mesothelioma and other types of cancer. However, the difficulty of distinguishing between malignant mesothelioma and a benign proliferation of cells is often overlooked.
Reactive mesothelial hyperplasia or proliferation is characterized by unusual cell growth in the mesothelium. While it is not malignant, mesothelial hyperplasia may later become cancerous, leading to uncomfortable and often life-threatening symptoms. An accurate diagnosis is important for timely and proper treatment and to avoid a benign proliferation developing into a malignancy.
What is Mesothelial Hyperplasia?
Hyperplasia, also known as mesothelial proliferation, is any increase in the number of cells in the mesothelium. A proliferation of cells in tissues that don’t normally grow and divide rapidly is not necessarily indication of cancer. Simple irritation of the tissue can cause cells to proliferate and produce benign tumors. However, sometimes there is no clear cause of hyperlasia.
What Causes Benign Mesothelial Proliferation?
While reasons for mesothelial hyperplasia is not always clear, there are several potential triggers. 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. In this area, it can be triggered by infection, inflammation, ovarian abscesses, or a buildup of fluid in the peritoneum.
Diagnosing Mesothelial Hyperplasia
Hyperplasia can be detected by examining biopsy samples under a microscope. A doctor may order a biopsy based on symptoms and imaging scans. To extract an effective sample, a medical professional will insert a long, thin needle into the chest cavity to remove a sample of pleural tissue or into the abdomen for tissue from the peritoneum. Once the sample has been extracted, a pathologist will examine the sample to determine if there is proliferation of the mesothelial cells.
Hyperplasia can be detected when normally elongated mesothelial cells appear more cubical in shape, 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.
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. Also, 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 give a diagnosis of atypical mesothelial hyperplasia and then continuing testing for signs of malignancy.
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 to examine. When the hyperplasia can be seen invading other tiussues in biopsy samples, this is a strong indication the growth is malignant.
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 the 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 a mesothelial proliferation is benign, there may be no treatment needed. 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 no cause can be determined, 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 progress of the hyperplasia. Regular screenings can track growth and catch signs of malignancy as early as possible.
Page Medically Reviewed and Edited by Anne Courtney, AOCNP, DNP
Anne Courtney has a Doctor of Nursing Practice degree and is an Advanced Oncology Certified Nurse Practitioner. She has years of oncology experience working with patients with malignant mesothelioma, as well as other types of cancer. Dr. Courtney currently works at University of Texas LIVESTRONG Cancer Institutes.