Evaluation of Malignancy Criterias in Dogs Melanocytic Neoplasms

Abstract

Melanoma is a type of skin cancer which is very aggressive in humans and dogs. Melanocytic tumors are common in the dogs, acconting for 3% of all neoplasms and up to 7% of all malignant tumors. The aim of this research was to evaluation of morfological aspects and malignancy criterias of the spontaneous melanocytic neoplasms in dogs. 18 tumors samples from skin and ocular areas of dogs were used. Evaluation of malignancy criterias of the melanocytic tumors was made by histopathology exams. Tumor location, histological cells type, stromal invasion, level of invasion according by Clark classification mitotic figures, presence of necrosis, lymphocyte infiltration, junctional activity, the presence of the tumors cell in the superficial layer, were recorded for each case. The head (33 %), the limbs (22 %) and the thoracic area (22 %) were the most common sites. Most melanocytic neoplasm were malignants (16 of 18 cases), composed of spindle cells (28 %), epithelioid cells (28%) and a mixture of epitheliod and spindle cells (17%) were common. We found only 2 cases of benign tumors. The mitotic index, cytological atypia, the high invasion level of the tumor and necrosis confirmed the malignancy in all cases of melanoma. In conclusion, the results of our study show that majority of all melanocytic tumors from dogs were represented by melanomas. The histological features used for the histological diagnosis of melanoma are not present in benign melanocytic tumors.