DISEASE IN WILDLIFE OR EXOTIC SPECIES Primitive Neuroectodermal Tumour in a Striped Dolphin (Stenella coeruleoalba) with Features of Ependymoma and Neural Tube Differentiation (Medulloepithelioma) J. L. Baily * , L. R. Morrison † , I. A. Patterson ‡ , C. Underwood * and M. P. Dagleish * *Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Near Edinburgh EH26 0PZ, † Veterinary Pathology Unit, Royal (Dick) School of Veterinary Studies and Roslin Institute, Easter Bush Campus, University of Edinburgh, Midlothian EH25 9RG and ‡ Agri-Food and Biosciences Institute, Veterinary Sciences Division, Stoney Road, Stormont, Belfast BT4 3SD, UK Summary Primary brain tumours in cetaceans are rare with only four reported cases of intracranial tumours in the sci- entific literature. A juvenile female, striped dolphin live-stranded at Whitepark Bay, Co Antrim, Northern Ireland, UK, and died after an unsuccessful attempt at refloatation. Necropsy examination revealed a large, soft, non-encapsulated friable mass, which expanded and replaced the frontal lobes, corpus callosum and caudate nucleus of the brain and extended into the lateral ventricles, displacing the thalamus caudally. Micro- scopically, this comprised moderately pleomorphic neoplastic cells arranged variably in dense monotonous sheets, irregular streams, ependymal rosettes, ‘ependymoblastomatous rosettes’ and multilayered to pseudos- tratified tubules. Liquefactive necrosis, palisading glial cells, haemorrhage and mineralization were also observed. Immunohistochemically, the neoplastic cells expressed vimentin but not S100, glial fibrillary acidic protein, cytokeratin, neuron-specific enolase or synaptophysin. Based on these findings a diagnosis of primitive neuroectodermal tumour was made. Monitoring and recording such cases is crucial as neoplasia may be related to viral, carcinogenic or immunosuppressive chemical exposure and can ultimately contribute to assessing the ocean health. Ó 2013 Elsevier Ltd. All rights reserved. Keywords: central nervous system; neoplasia; primitive neuroectodermal tumour; Stenella coeruleoalba Primary brain tumours in cetaceans are rare with only four reported cases: a cerebral lipoma in a hump- back whale (Megaptera novaeangliae)(Pilleri, 1966); a cerebral neurofibroma in a fin whale (Balaenoptera physalus)(Pilleri, 1968); a poorly differentiated carci- noma in the brainstem of a Beluga whale (Delphinap- terus leucas)(Ridgway et al., 2002); and a microcystic meningioma in a short-beaked common dolphin (Delphinus delphis)(Miclard et al., 2006). Additionally, Siebert et al. (2010) described intracranial metastases of a gastric squamous cell carcinoma in a harbour porpoise (Phocoena phocoena). The scarcity of reports may represent a genuine low incidence, lack of access to cases due to death at sea, advanced autolysis or technical difficulties in examining the brain. Marine mammals are long-lived top level predators recog- nized as sentinels for ocean health (Bossart, 2011) and since neoplasia may be related to viral, carcino- genic or immunosuppressive chemical exposure, it is important to record and monitor these cases (Newman and Smith, 2006). Striped dolphins (Stenella coeruleoalba) are social an- imals found throughout temperate and tropical wa- ters in dense schools of, on average, 100 animals. Correspondence to: J. L. Baily (e-mail: johanna.baily@moredun.ac.uk). 0021-9975/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jcpa.2013.06.003 J. Comp. Path. 2013, Vol. 149, 514e519 Available online at www.sciencedirect.com www.elsevier.com/locate/jcpa