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Microcystic meningioma in a dolphin (Delphinus delphis): immunohistochemical and ultrastructural study
J Miclard1, K Mokhtari, G Jouvion
1Unité d'Anatomie Pathologique, UMR 703 INRA/ENVN, Ecole Nationale Vétérinaire de Nantes, BP 40706 Nantes Cedex 03, France.
Abstract:
A wild common dolphin was found stranded on the French Atlantic coast. At necropsy, an intracranial grey- to tan-coloured mass (7 x 5 x 4 cm) was found at the right cerebellopontine angle, compressing the right cerebellar hemisphere, the brainstem and the occipital lobe of the right cerebral hemisphere. Microscopically, the tumour was composed of small lobules of polygonal to elongated neoplastic cells with multifocal areas of stellate and vacuolated cells. Neoplastic cells strongly expressed vimentin, S-100 protein and neuron-specific enolase. They were rarely positive for cytokeratin. Ultrastructurally, the neoplastic cells displayed all the diagnostic features of meningiomas and in some areas showed long cytoplasmic processes delimiting extracellular spaces. The immunohistochemical and ultrastructural features were consistent with the histopathological diagnosis of a microcystic meningioma. This is the first report of a meningioma in dolphins or in any other cetacean species.
Insights
A rare brain tumor, a microcystic meningioma, was discovered in a stranded common dolphin. This marks the first documented instance of a meningioma in any dolphin or cetacean species.
Area of Science:
- Veterinary Pathology
- Marine Mammal Medicine
- Neoplasia Research
Background:
- Stranding events provide opportunities for wildlife health investigations.
- Intracranial pathologies can significantly impact marine mammal health and survival.
- Cetacean neoplasms are infrequently reported, making each case valuable.
Observation:
- A wild common dolphin stranded on the French Atlantic coast was examined post-mortem.
- A significant intracranial tumor, measuring 7 x 5 x 4 cm, was identified at the right cerebellopontine angle.
- The mass compressed critical brain structures including the cerebellum, brainstem, and occipital lobe.
Findings:
- Histopathological analysis revealed a tumor composed of neoplastic cells with characteristic features of meningioma.
- Immunohistochemistry showed strong expression of vimentin, S-100 protein, and neuron-specific enolase.
- Ultrastructural examination confirmed the diagnosis of a microcystic meningioma, a rare subtype.
Implications:
- This study reports the first-ever meningioma diagnosed in a dolphin and any cetacean species.
- Understanding cetacean neoplasms contributes to the broader knowledge of comparative oncology.
- Further research may elucidate the prevalence and etiology of meningiomas in marine mammals.
