Desmoplastic mesothelioma (DMM) is a rare form of malignant mesothelioma in which 50% or more of the tumour is fibrous and has a low cell content. It produces thick nective tissue in the lungs as well as other areas of the body. This type of tumour lies in between biphasic and sarcomatous subtypes of mesothelioma, as its own group of tumours known as desmoplastic mesothelioma. These tumours consist of dense, hypocellular collagenous tissue throughout 50% or more of the tumour.
“Although rare, malignant mesotheliomas have assumed great importance during the past two decades because of their increased incidence, especially among persons with previous exposure to asbestos. Up to 90% of mesotheliomas are associated with asbestos within occupationally exposed groups” and because of the long latency period of between 25 and 45 years for the effects of exposure to asbestos to develop into mesothelioma, it is expected that the number of cases will continue to increase until 2000 and beyond.” (G. E. Wilson et.al., “Desmoplastic malignant mesothelioma: a review of 17“)
Desmosplastic mesothelioma can be extremely difficult to interpret and the correct diagnosis of malignancy may not be suspected. This form of mesothelioma is difficult to distinguish from reactive pleural fibrosis because of associated extensive collagen fibrosis, making it additionally difficult for oncologists to properly diagnose. Even when a needle biopsy is performed, the fibrous tissue may come back benign and allow the disease remain untreated for many years, where it may spread througout other parts of the body, as the disease progresses.
Though rare, it is important for the medical professional to distinguish it from a pleural plaque, nonspecific reactive pleural fibrosis, pleurisy, rheumatoid disease, or, rarely, spindle cell sarcomas, so that the proper treatment plan is followed. In addition to the difficulties medical professionals have in diagnosing this particular type of cancer, the tumors may hide within the abdominal area, because the abdominal area is primarily made up off internal organs and fatty tissue which may make the fibrous tumors hard to identify and diagnose. Desmoplastic mesothelioma has a specific storiform collagen pattern, collagen necrosis, bland acellular collagen and focal cytological signals of malignancy which can futher identified through further testing.
Desmoplastic mesothelioma is characterized by areas within the tumor consisting of dense bundles of hyalinised collagen arranged in interweaving bundles, whorls, or a storiform pattern. The irregular arrangement of the collagenous component is of diagnostic importance. Invasion of lung parenchyma, adipose tissue, or chest wall confirms the diagnosis. Apart from malignant mesothelioma, other epithelial and mesenchymal tumours may contain desmoplastic areas.
Desmoplastic Mesothelioma can cause extreme chest pain in patients and/ or cause a build up of fluid in the lungs. The pain associated with this particular subgroup of mesothelioma can be very severe and may cause the hospitalization of the patient.
Treatment plans for desmoplastic mesothelioma revolve around providing the patient with pallative care, and prolonging the patient’s life through the use of chemotherapy, radiation and nutritional therapy, multimodality treatment, and/or drug therapy.