+ 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