Choroidal melanoma in a cat: first case report

CONGRES ESVO / ECVO / AFOV / AFVAC-GEMO / SFEROV
Versailles 2008

Autors :
V. Mahé*, E. Guery**, A. Deviers**, M. Delverdier**, C. Vallin***, I. Raymond-Letron**.
*:Veterinary clinic, 344 bd de la paix, 64000 PAU, France
**:Department of Clinical Sciences, National Veterinary School, 23 chemin des Capelles, B.P. 87614, Toulouse Cedex 3, France.
***:Veterinary ultrasonography, 40390 St Martin de Seignanx, France

Purpose :
This study aims to report a case of choroidal melanoma in the feline species.

Method :
Complete ophthalmic examination, ultrasonography, and histopathology were
performed.

Results :
An 11 year-old European male spayed cat was presented for anisocoria. On physical examination, the animal was healthy and alert, and abnormalities were limited to the right eye. On that side, the direct pupillary light reflexe was sluggish and the menace response was equivocal. Ophthalmic examination revealed a retrolental pigmented mass located in the in the inferonasal part of the vitreous cavity. In addition, a retinal detachment was visible next to the mass on ophthalmoscopic examination. Ultrasonography performed with a 6.6 MHz, demonstrated the presence of a hyperechoic conical shaped mass protruding from the choroid into the vitreous cavity. The total retinal detachment was also confirmed. Retromandibular lymph node cytology and thoracic radiography did not show evidence of metastasis. As a neoplastic process was suspected enucleation was performed. Microscopic examination of the excised globe revealed a large heavily pigmented intraocular neoplastic mass arising from the choroid, behind the ora ciliaris, bulging into the vitreous, producing a dome shaped mass. Overlying the mass, the retina was detached and atrophied. The tumour did not invade the neurosendory retina and sclera. The tumour was composed primarily of large round plump cells. Nuclear atypia and mitotic figures were not seen. Examination of serial sections of the iris and ciliary body did not reveal neoplastic cells in the anterior uvea. The histological diagnosis was benign choroidal melanoma (melanocytoma). Conclusion: To the author’s knowledge, this is the first report of a choroidal melanoma in the feline species. In this case, the clinical management and biological behaviour resemble those of the great majority of canine choroidal melanomas. The clinical and histopathological characteristics seem to correspond to a “benign” tumour behaviour (choroidal melanocytoma). Choroidal melanoma should be included in the differential diagnosis of posterior segment tumours in the cat.