Abstract
Introduction: :
Background: Benign and malignant tumors of melanocytic origin are the most common primary canine intraocular neoplasms, representing an important disease in the veterinary community. They have distinct distribution, clinical features and prognosis when compared to human melanocytic neoplasms. In this report, we aimed to study a series of pigmented tumors of dogs and classify them based on histopathological criteria.
Methods: :
A series of canine intraocular pigmented tumors was reviewed. Formalin-fixed, paraffin-embedded specimens were cut and stained with H&E. Bleached sections were also prepared in order to evaluate cytological features. Histopathological parameters that were studied included tumor location, degree of pigmentation (negative, + or ++), extent of tumoral necrosis (negative, + or ++) and final diagnosis.
Results: :
The data consisted of 22 eyes of 22 dogs. Sixteen tumors were anterior (iris and ciliary body), while the other 6 involved the entire eye. The majority of specimens were heavily pigmented (n=16) while the remaining specimens (n=6) were mildly pigmented. There were no amelanotic cases. Fifteen cases showed extensive necrosis, 6 cases had limited necrosis, and one case had no necrosis. Half of the samples (n=11) were considered benign and all of those were melanocytomas. The malignant group was composed of 10 melanomas (2 spindle, 3 mixed, 5 epithelioid) and 1 adenocarcinoma of the ciliary epithelium. Of the 10 melanoma cases, five had areas that were histopathologically identified as melanocytomas.
Conclusions: :
We presented a large series of canine intraocular pigmented tumors. There was a striking predilection for the anterior part of the eye. Most tumors were heavily pigmented and the majority showed extensive areas of necrosis. The proportion of melanocytomas is much greater than what is reported in humans. Half of the melanomas seemed to have arisen from melanocytomas, suggesting that these benign tumors can undergo malignant transformation.
Keywords: melanoma • tumors