Peritoneal
- Mesotheliomas
- Malignant - implantation rather than metastasis
- Mainly cattle and dogs, occasionally in other species
- Can be congenital in calves
- Arise from serosa of pericardial, pleural and peritoneal cavities
- Multiple small nodules, may be pedunculated, few milimeters to few centemeters, may present as villous projections
- May be associated with milky or bloody effusions
- Histologically usually appear similar to adenocarcinoma (papillary) or fibrosarcoma (spindle cells)
Image of glandular type mesothelioma in a cat from Cornell Veterinary Medicine
Pleural
- Has been found in cat, dog, cow, goat and horse
- Arise from pericardial, pleural and peritoneal surfaces
- May be related to inhalation of asbestos
- Grossly:
- Multiple discrete nodules
- Microscopically:
- Can appear as a carcinoma or fibrosarcoma depending on which tissue, covering or supporting, is predominant in the neoplasm
- Rarely metastasise but are considered malignant