Title
Clinical, Gross, and Histopathologic Findings in a Cluster of Six Cases of Malignant Peripheral Nerve Sheath Tumor in Senegal Bichirs (Polypterus senegalensis)
Author(s)
Newton, A.L.;Gustavsen, K.A.;Paré. J.A.;McAloose, D.
Published
2015
Abstract
Bichirs (Polypterus spp.) are evolutionarily ancient freshwater fish native to central Africa. They
are popular exhibit fish due to their strikingly primitive appearance and retained physiologic
characteristics, including obligate air-breathing with true lungs.2 From 2011 through 2014, six of
19 adult Senegal bichirs (Polypterus senegalensis) in the Wildlife Conservation Society collection
developed large, disfiguring tumors resulting in death or euthanasia. Tumors were located in the
musculature of the dorsal or lateral body wall. The most advanced cases ruptured through the skin,
exposing an exophytic, broad-based mass that was not amenable to resection. Observed clinical
signs were limited to mildly decreased activity, though at necropsy some fish were in thin condition
and most had empty digestive tracts. Necropsy findings included a second, earlier stage tumor in
two cases, coelomic invasion in one case, and metastatic disease in one case. Histologically, these
neoplasms were infiltrative into the epaxial muscles, and in one case invaded and effaced
vertebrae. One fish had evidence of secondary bacterial sepsis. The histologic diagnosis in each
case was malignant peripheral nerve sheath tumor or neurofibrosarcoma; tumor locations
suggested an origin from the spinal nerves. Similar tumors occur spontaneously in a number of
fish species, and an infectious etiology has been demonstrated in epizootic peripheral nerve sheath
tumors of bicolor damselfish (Stegastes partitus).1,3 The high prevalence of the same neoplasm in
this bichir colony is suggestive of an infectious etiology, though an agent has not yet been
identified.
Keywords
Malignant peripheral nerve sheath tumor;neoplasia;neurofibrosarcoma;Polypterus senegalensis;Senegal bichir
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PUB15638