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What Is Desmoplastic Mesothelioma?

Desmoplastic mesothelioma is a subtype of the sarcomatoid form of mesothelioma. Sarcomatoid refers to long and spindle-shaped cells. It is a rarer and more deadly form of mesothelioma cancer.

Desmoplastic mesothelioma cells graphic

Dense fibrous tissue and reduced cellular features characterize the desmoplasia variant. This subtype has a poor prognosis and can occur in all types of sarcomatoid mesothelioma.

Desmoplastic cells are not well-differentiated and lack defining qualities or patterns. These types of mesothelioma cells form dense nodules of connective tissue within tumors. This makes diagnosis more challenging.

This rare variation is present in 5% to 10% of all malignant mesothelioma cases. Asbestos exposure is the disease’s primary cause. It can develop in the different types of mesothelioma cancer.

Diagnosing Desmoplastic Mesothelioma

A biopsy of tumor tissue diagnoses desmoplastic mesothelioma. Doctors take a large tissue sample so they can review enough cells to make a diagnosis. When diagnosing mesothelioma, a sample of tumor tissue is essential. It determines the cell type and treatment options.

Fibrous regions of this tumor can hide cell variations that lead to an accurate diagnosis. Physicians sometimes misdiagnose desmoplastic malignant pleural mesothelioma as fibrous pleurisy. Other misdiagnoses include pleural fibrosis, rheumatoid disease or spindle cell sarcoma.

Desmoplastic Mesothelioma Diagnostic Criteria

Doctors look for the following characteristics to diagnose desmoplastic mesothelioma:

  • At least 50% of the tumor forms nodules of dense fibrous tissue.
  • Areas of increased cellularity are present with sarcomatoid characteristics.
  • Neoplastic spindle cells have spread to the lung or chest wall.
  • Metastasis has occurred in nearby fat tissue, skeletal muscle or the lung.
  • The p53 tumor suppressor gene protein is present.

When desmoplastic mesothelioma spreads to other areas, it can look bland. This causes doctors to mistake the cells as benign fibrous tissue. Imaging scans such as a CT or MRI may help pathologists identify metastasis and diagnose DMM in challenging cases.

In 2017, pathology researchers discovered a protein called GATA-3. It differentiates desmoplastic mesothelioma from sarcomatoid lung cancer. It is present in many mesothelioma cases and often absent in lung carcinoma cases. This factor aids physicians when staging pleural mesothelioma.

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Symptoms of Desmoplastic Mesothelioma

Dense and fibrous areas may produce symptoms like pulmonary fibrosis, such as chest pain and a buildup of fluid in the lungs. But, these symptoms develop in every case of mesothelioma.

The tumor’s cell type doesn’t affect symptoms of mesothelioma. Pleural mesothelioma patients experience shortness of breath. Peritoneal patients often present with abdominal pain.

Desmoplastic Mesothelioma Treatment

The treatment options for desmoplastic mesothelioma include immunotherapy, chemotherapy and radiation therapy. These can kill cancerous cells to shrink tumors and limit spreading. Treatment depends on the patient’s age and health.

Immunotherapy with nivolumab (Opdivo) and ipilimumab (Yervoy) is the first-line treatment. Chemotherapy with cisplatin and pemetrexed (Alimta) follows. Radiation can shrink painful chest wall tumors.

This type of mesothelioma is not treated with surgery. It has a high risk of returning within several months. It is rare for a surgeon to recommend it to desmoplastic patients. A few case reports show some patients lived several months longer following surgery. They were desmoplastic patients with early-stage or localized tumors.

Treatments aim to reduce symptoms, prolong survival and improve quality of life. Doctors recommend pleurodesis or paracentesis to remove fluid from the lungs or abdomen.  

Prognosis of Desmoplastic Mesothelioma

The prognosis of mesothelioma with desmoplasia is not favorable. It resembles other types of sarcomatoid cancer. The disease subtype is tricky to diagnose. Patients often have advanced disease at diagnosis. The life expectancy of patients with this subtype is less than one year.

A seven-year study evaluated 255 patients with mesothelioma between 1982 and 1989. Researchers identified 17 cases of the desmoplastic subtype. Of those, 11 were sarcomatoid and six were biphasic, comprising both sarcomatoid and epithelial cell types.

The mean survival from the onset of symptoms to death was 5.8 months for the sarcomatoid variant and 6.8 months for the biphasic variant. Other studies show an average life expectancy of 3.8 months.