Sebaceous gland epithelioma with potential malignancy in a dog

Sebaceous gland tumors consist of neoplastic proliferations of sebaceous gland cells located around hair follicles in the dermis. These tumors are subclassified as sebaceous epithelioma, sebaceous adenoma, sebaceous adenocarcinoma and nodular hyperplasia. In this case report, a nodular growth in the sacral region of an eight-year-old male Belgian Malinois dog was presented. Macroscopically, the nodular mass had a slightly soft consistency, grayish-white, and dark red-black appearance. The mass was measured in the dimension of 2x1x1 cm. Histopathologically, the tumor was observed to have a multilobular structure shaped by neoplastic cell islands. The tumor consisted mainly of eosinophilic cells with small cytoplasm resembling epithelial basaloid cells and to a lesser extent differentiated sebocytes. The parenchyma of the tumor consisted of irregular islets containing a small number of mature sebocytes. Their nuclei are oval with one to three small nucleoli. Immunohistochemically, tumor cells for Ki67 antibody showed strongly positive immunoreactivity. Based on the histopathological and immunohistochemical features, the tumor was diagnosed as sebaceous epithelioma having, a potential malignancy. Since no case of sebaceous epithelioma with malignant potential has been reported in our country, we aimed to present the case with histopathological and immunohistochemical features.