Desmoplastic Mesothelioma

What is Desmoplastic Mesothelioma?

Desmoplastic mesothelioma is a rare cell variant of malignant mesothelioma that occurs in patients with sarcomatoid cancer cells. About 5 to 10 percent of mesothelioma patients develop the desmoplastic variant.

Mesothelioma is one of the deadliest forms of cancer that affects the lungs, abdomen, and the heart. Cell types and cell variants of mesothelioma differ among patients based on a variety of factors. In general, all patients start their early mesothelioma journey experiencing similar symptoms. To distinguish which cell type or cell variant a patient has, doctors must recognize different characteristics.

Sarcomatoid mesothelioma cells appear long and spindle-shaped. A change in sarcomatoid cell DNA creates this fatal desmoplastic cell variant. Doctors characterize desmoplastic malignant mesothelioma (DMM) cells as having reduced cellular features when present in dense fibrous tissue. Using a microscope, desmoplasic cells appear to lack defining patterns.

Diagnosing DMM can be tough due to how the cells affect connective tissue. Tumors and cancer cells are hard to find in dense connective tissues, making diagnosis more challenging. Recent advances in pathology help doctors recognize the variant using the GATA-3 protein.

What is Desmoplasia?

Desmoplasia is a reaction that occurs in the form of fibrous tissue growth around a disease. Benign, non-malignant conditions can cause desmoplasia in rare cases.  Desmoplastic mesothelioma can be characterized by a high concentration of fibrous connective tissue. To understand desmoplasia, you need to understand the typical structure of normal tissue. In a healthy lung, epithelial cells are organized in sheets that are less than 1/10 of a millimeter thick.

Beneath the epithelial layer is loose connective tissue and muscle. Mesothelial cells line the outside of the lung to protect it from injury and infection. However, when tumors form they produce signals that tell nearby cells to grow and divide abnormally, damaging surrounding tissues in the process.

Diagnosing DMM

Doctors diagnose desmoplastic mesothelioma by collecting a biopsy sample of tumor tissue. Pathologists review the tissue sample in the lab to determine if it contains the desmoplastic cell mutation.

Diagnosing desmoplastic mesothelioma can be tricky because of the fibrous tissue that develops near the tumor. Doctors sometimes misdiagnose the cell mutation as pleural fibrosis or other diseases.

To help prevent a mesothelioma misdiagnosis, doctors use specific diagnostic criteria. Desmoplastic mesothelioma diagnostic criteria include:

• The tumor contains the p53 suppressor gene.
• At least half of the tumor contains dense fibrous tissue.
• Sarcomatoid characteristics are present in areas of increased cellularity.
• Mutated cells spread to the lung or chest lining via neoplastic spindles.
• Metastasis to nearby skeletal muscle, tissue, or a lung occurs.

Imaging scans, including CT and MRI, also help identify the dense tissues of DMM.

Is Desmoplastic Mesothelioma Curable?

Desmoplastic mesothelioma is not curable. Because patients are often diagnosed with DMM in the advanced stages of mesothelioma, the prognosis is not typically favorable. The life expectancy of patients with the DMM subtype is less than one year on average.

Treatment for the rare variation typically includes immunotherapy, chemotherapy, and radiation therapy meant to kill cancer cells and shrink tumors. However, treatment options depend on the characteristics of the patient, including age and overall health. Surgery is rarely used to treat DMM because patients are typically not in good health to undergo an invasive treatment option.

Desmoplastic Malignant Pleural Mesothelioma Symptoms

Most symptoms of DMM result from the high concentration of dense connective tissue. The fibrous areas of dense tissues produce symptoms similar to other pulmonary diseases, such as chest pain and fluid buildup in the lungs.

Common symptoms of pleural mesothelioma include chest pain, coughing up blood, difficulty breathing, loss of appetite, and shortness of breath. Not every patient experiences the same reactions to mesothelioma and its cell variants. Generally, patients may find themselves eligible for better treatment options the earlier they receive a diagnosis.

One Woman’s Symptoms

In one case study, a 72-year-old woman experienced a lack of appetite, chest pain, and fatigue for around 6 months before seeing a doctor. A physical examination, a pulmonary function test, and an x-ray revealed thickening around the left lining of the lung. The unusual imaging scans later determined the cause of symptoms to be DMM.

The woman’s exposure to asbestos occurred during her history of whitewashing interior walls in her house with asbestos several years prior. The use of asbestos on inner walls, pottery, and powder was common in places where the woman lived in Turkey.