Melanoma of the Iris, Ciliary Body and Choroid in a Dog’s Poodle

Abstract

 Background: Melanoma is a primary ocular neoplasm that may affect the iris, ciliary body, the choroid coat and others components of the eye. The ocular melanomas have a low metastatic level in dogs when compared to cats. Old animals are more affected than the young ones and there is no breed predilection. A complete eye examination and ocular ultrasound will lead to the diagnosis that will be further confirmed through histopathology. Current treatment of choice is based on the size and the structures involved by the tumor that can range from local resection to orbital exenteration. The objective of this study is to report a case of iris melanoma involving the ciliary body and the choroid coat of a Poodle, emphasizing its clinical manifestation, diagnosis and treatment.

Case: This study reports a case of an intact male canine Poodle, 15 years old, weighing 5 kg that was referred for care to the Veterinary Teaching Hospital of the Federal University of Santa Maria, Brazil. The owner initially presented a history of a progressive increase dark-colored intraocular volume in the right eye iris of the dog. On the clinical examination, no abnormality was found. On the ophthalmic examination, the right eye possessed misshapen pupil, hyperemia ocular conjunctiva (+) and diffuse corneal opacity (+) with paracentral pigmentation between 7-10 hour. On biomicroscopic ex­amination, using a slit lamp, it was observed an iris distension that was protruding directly into the anterior chamber and a diffuse opacity of the lens. Intraocular pressure was eight mmHg. B-mode ultrasonography revealed a mass involving the iris, ciliary body and the choroid coat with perilesional retinal detachment, suggesting iris ciliary body and choroid mela­noma. Due to the bad prognosis of the affected eye, the patient underwent to orbital exenteration procedure. The extracted eyeball was placed in 10% formalin and sent for histopathological examination, which was later reported as showing an iris melanoma involving the ciliary body and the choroid coat. The patient was re-examined six months postoperatively and no neoplasm recurrence signs were observed.

Discussion: The animal stated in this report showed an increased volume of the right eye and dark pigmentation involving the iris. As highlighted by the actual literature, the size of this kind of neoplasm can vary from small to larger nodules and it can causes relevant anatomical changes. The pigmentation in these cases may vary from dark colors (black or brown) to white, for example, the amelanotic melanomas. In this report it was observed a nodular staining quite blackened pig­mentation. This kind of cancer involves mainly not neutered male dogs, with breed predilection as the German shepherd dogs, Golden Retrievers, Labrador Retrievers and also Poodles, as reported in this case. The treatment suggested by the literature, can range from diode laser therapy to microsurgical resection with enucleation or exenteration, depending on the size of the affected region and structures involved. The treatment of choice in this patient was the orbital exenteration because of the capacity of this tumor to spread throughout the uvea and it was not sure whether scleral infiltration could already exist, although the enucleation could also be indicated. However, through the histopathological examination, it could be confirmed that the neoplasm was located only at iris, involving also the ciliary body and choroid coat without sclera leakage, so there would be no need for exenteration. The average age of the patients is around nine years old ac­cording to published reports, namely older animals as the patient here described. The orbital exenteration technique, with good safety margin resection, proved to be efficient for the surgical treatment of iris melanoma involving the ciliary body and the choroid coat.

Keywords: ophthalmology, neoplasm, uvea.