Pathophysiology

•mesothelioma is rare

•mesothelioma is a tumor arising from mesothelial cells of the pleural and peritoneal cavities

•sites: thoracic cavity, pericardium, abdominal cavity, and vaginal tunic of the scrotum

•etiology: congenital form and secondary to asbestos

•asbestos is a complete carcinogen, initiator, tumor promoter, and causes chromosomal damage

•asbestos is composed of chrysotile and amphibole fibres

•amphibole fibres are responsible for the increased risk of mesothelioma

•histologic types of mesothelioma: epithelial (most common), mesenchymal, and mixed

•epithelial mesothelioma resembles carcinoma or ADC

•mixed mesothelioma (= sclerosing mesothelioma): male dogs and GSD are over-represented

•cystic mesothelioma has been reported in 1 dog

Clinical Signs

•pleural and peritoneal effusion are the most common presenting signs

•extensive effusion due to exudation from tumor surface and tumor-obstructed lymphatics

•acute tamponade and right-sided heart failure with pericardial mesothelioma

•sclerosing mesothelioma: restrictive disease resulting in vomiting and urinary disease

Diagnosis

•ultrasonography and survey radiographs are not usually useful as diffuse disease is more common than space-occupying lesions

•mesothelial cells can exfoliate under many circumstances resulting in difficulty differentiating physiologic mesothelial cell proliferation from neoplasia

•pericardial fluid pH may differentiate benign and malignant effusions with pH in dogs mesothelioma and HSA > 7.5 while benign effusions have a pH < 6.5

•fibronectin concentration are increased with neoplasia (sensitive but not specific)

•definitive diagnosis: histopathology ± immunohistochemistry

Treatment

•pericardiectomy provides palliation for animals with cardiac tamponade

•intracavitary cisplatin: well-tolerated with decreased fluid accumulation

•intracavitary cisplatin combined with systemic chemotherapy may be promising

•intracavitary cisplatin results in resolution of effusion after 1-2 doses with DFI ranging from 129 days to 27 months

Prognosis

•MST 13.6 months for pericardial mesothelioma following pericardiectomy, with 1-year survival rate 80% and 2-year survival rate 40%

•recurrent pleural effusion > 30 days after pericardiectomy associated with a worse prognosis and < 120 days more likely to be associated with mesothelioma