Occasionally, mesothelioma mimics benign tumorMalignant pleural mesothelioma (MPM) is a deadly tumor that begins in the sac surrounding the lung. Does the word "malignant" indicate that there's such thing as benign pleural mesothelioma?
In a way, yes. It's very rare, and with time it usually becomes malignant. It's called a pleural adenoma, and it's so uncommon that experts say most cases are actually just mesothelioma in disguise. Recently, a team of Texan oncologists dedicated a medical review to the subject.
Adenomas are benign
Usually, pleural adenomas are found accidentally, often during routine MRIs or during screening for some other thoracic disease. For example, a paper published in a 1996 issue of the American Journal of Surgical Pathology described the discovery of two pleural adenomas.
In both cases, doctors found the growths while performing surgery for other respiratory diseases (lung cancer and histoplasmosis).
"Adenomatoid tumors are regarded as a benign variant of mesothelioma," the authors explained. "Despite the abundance of mesothelial cells in the pleura, adenomatoid tumors are apparently extremely rare in this location. Separation from malignant lesions such as adenocarcinoma and epithelioid hemangioendothelioma is important."
Why might it be so crucial to distinguish between MPM and pleural adenomas? The answer is self-evident: Mistaking mesothelioma for a benign disease would put patients' lives at risk. Likewise, the reverse would subject people with a benign condition to unnecessarily extensive treatment.
This is precisely why scientists from the MD Anderson Cancer Center in Houston, Texas, recently wrote about adenomatoid malignant mesothelioma (AMM).
Appearances can be deceiving
The team noted that, in all, it had treated 10 cases of AMM - that is, a disease that appears to be a benign pleural adenoma but is revealed to MPM. Researchers emphasized that AMM is deadly. Even though most cases involved major surgery to remove tumor mass, just one patient lived more than a year beyond diagnosis.
The authors emphasized that cellular testing and tissue biopsies are essential in proving that a tumor is AMM. However, they noticed that, in some cases, the cellular tests indicated (falsely, as it turned out) a benign adenoma. In those cases, the team said, the giveaway was the fact that the tumor was invading nearby organs and that biopsied cells were dividing rapidly.
Researchers added that, in three instances, patients had a history of asbestos exposure, which increased the suspicion that the pleural growth was malignant.
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