Multiple intra-abdominal serosal myxosarcomas in two koalas (Phascolarctos cinereus)
Gonzalez Astudillo, V, Schaffer-White, A, Allavena, R & Palmieri, C 2015, Journal of Comparative Pathology, vol. 152, pp. 183-286.
Post-mortem examinations performed on two koalas revealed a thick accumulation of fluid in the abdomens. Many hard lumps filled with fluid were also found spread across the abdominal cavities. When examined under the microscope the lumps were found to contain cancer cells.
One female and one male koala were examined; the two were abnormally thin and their fur discoloured. In the abdomen of each animal, up to 200 mL of fluid was found. Multiple hard lumps 1-3mm in diameter were scattered across the abdominal cavity. The cavity was also full of sticky fibres joining the organs to the intestines. A few parasitic worms (Bertiella obesa) were present in the koalas’ intestines. The affected tissues were stained and examined under the microscope. The abdominal tissues had neoplastic cells protruding from the surface. Red blood cells were of unequal size and the cancer cells had unevenly sized nuclei. Many blood vessels were identified supplying the cancer growth, and similar cells were found on the liver and on the walls of the abdominal cavity. A diagnosis of a malignant connective tissue tumour, or serosal myxosarcoma, was made.
Myxosarcoma is a rare diagnosis and has been mainly described in dogs. Although there have been previous reports of myxosarcoma in koalas, this study describes the first serosal myxosarcoma originating in the abdominal cavity of the koala. These kinds of tumours secrete a sticky type of protein called mucin which explains why the fluid in the abdominal area was thick. Special staining allowed distinction from a different type of connective tissue cancer.
Disease associated with neoplasia is a common cause of sickness and death in koalas. This is the first report of a serosal myxosarcoma in koala. As the cancer is rare and hard to detect, it is unclear what factors may have caused it. More research is needed to investigate the cause of this disease and how it affects koala populations.
Summarised by Alexandra Selivanova
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