Primitive neuroectodermal tumour in a striped dolphin (Stenella coeruleoalba) with features of ependymoma and neural tube differentiation (Medulloepithelioma).

Primary brain tumours in cetaceans are rare with only four reported cases of intracranial tumours in the scientific 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. Microscopically, this comprised moderately pleomorphic neoplastic cells arranged variably in dense monotonous sheets, irregular streams, ependymal rosettes, 'ependymoblastomatous rosettes' and multilayered to pseudostratified 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.

The first report of disease in a basking shark (Cetorhinus maximus).

Few diseases have been reported in any species of shark and none in the basking shark (Cetorhinus maximus) despite the latter being the subject of targeted hunting for over two centuries. This is the first report to describe the clinical signs and gross and microscopical pathology in a diseased basking shark that was live-stranded on the east coast of Scotland. Pyogranulomatous meningoencephalitis was present together with multifocal, predominantly non-suppurative, myocarditis with myocyte necrosis, oedema and haemorrhage. Additionally, there was full thickness ulcerative and fibrinonecrotizing dermatitis with underlying granulomatous inflammation. The aetiology could not be determined, but the lesions were suggestive of an infectious process, possibly bacterial.