In 1980, doctors discovered desmoplastic malignant mesothelioma (DMM). DMM is a subtype of sarcomatoid malignant mesothelioma. It is thought to account for 5-10% of pleural mesothelioma patients, but is often challenging for doctors to diagnose.
Diagnosing Desmoplastic Mesothelioma
Under the microscope, DMM consists of dense collagen fibers in a “patternless” pattern, making it difficult to identify. Doctors diagnose DMM using a process called immunohistochemical staining. This broad spectrum staining identifies certain tumor markers, called cytokeratins, and is vital for the correct diagnosis.
Often, DMM is misdiagnosed as a benign tumor or disease. This can be detrimental to a patient because they will receive an innaccurate prognosis. With a benign misdiagnosis, patients may also receive less aggressive treatments than would be used if a malignancy was found. When a misdiagnosed patient is finally diagnosed correctly they may have fewer treatment options because of their disease progression.
- Pleural plaques: benign, patchy, fibrous thickening of the pleura
- Pleurisy: inflammation of the pleura
- Non-specific reactive pleural fibrosis: plaque or thick layer of non-expansible fibrous tissue that surrounds part or all of lung
- Solitary fibrous tumors: rare growths of soft tissue on the pleura that are mostly benign
How DMM Compares to Other Cell Types
DMM presents similarly to other cell types of pleural mesothelioma, with a few differences. In most cases, a patient with DMM will have little or no pleural effusion with cancer spread to distant organs or lymph nodes at time of diagnosis. A typical pleural mesothelioma diagnosis is characterized by large pleural effusions with regional lymph node involvement.
3 common symptoms of all cell types:
- 2Dyspnea (difficulty breathing)
- 3Pleural thickening
If doctors suspect a diagnosis of DMM, a video-assisted thoracoscopic surgery (VATS) should be completed. This minimally invasive procedure gives the surgeon the ability to look inside the chest wall and take biopsies of any abnormal findings. VATS also allows doctors to take a larger tissue specimen than other types of biopsies. A large enough tissue specimen must be collected to develop an accurate diagnosis through staining.
Currently, desmoplastic mesothelioma is treated with first line chemotherapy, a combination of cisplatin and Alimta. Recent studies have shown that adding bevacizumab (avastin) to first line therapy was advantageous for sarcomatoid or mixed histology mesothelioma.
Is Asbestos a Culprit?
Patients often question if desmoplastic mesothelioma, like malignant pleural mesothelioma, is caused by asbestos. The relationship between asbestos and DMM is still controversial. However, most patients have had a history of asbestos exposure and autopsies have revealed asbestos fibers in the thickened pleura.
Recent reports have suggested an increasing trend in malignant pleural mesothelioma cases.
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- Malignant mesothelioma of the pleura with desmoplastic histology: a case series and literature review. The National Center for Biotechnology Information (NCBI). Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5012075/. Accessed: 12/8/16.
- Solitary fibrous tumor. Mayo Clinic. Retrieved from: http://www.mayoclinic.org/diseases-conditions/solitary-fibrous-tumors/home/ovc-20253652. Accessed: 12/8/16.
- Desmoplastic malignant mesothelioma of the pleura: autopsy reveals asbestos exposure. The National Center for Biotechnology Information (NCBI). Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/12787316. Accessed: 12/8/16.
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