Canine Skin Tumours with Adnexal Differentiation: Histopathology and Immunohistochemistry

Thirty nine canine adnexal tumours were histologically and immunohistochemically analysed. They were classified as trichoblastomas, trichoepitheliomas, sebaceous adenomas and epitheliomas, hepatoid gland adenomas and epitheliomas, and aporcine adenocarcinomas. Moreover, hepatoid gland angioadenoma and angioepithelioma were recognised. Studies of follicular tumours revealed coexpression of cytokeratin MNF116 and LP34, but sebaceous and hepatoid gland tumours as well as apocrine adenocarcinomas showed differences in the expression of both cytokeratins. All the tumours were negative for vimentin except two hepatoid gland adenomas in which coexpression of vimentin and cytokeratin was observed. Positive reaction for neuron-specific enolase (NSE) was observed in follicular tumours, whereas expression of α-smooth muscle actin (α-SMA) was found only in apocrine adenocarcinomas. Moreover, the presence of NSE observed in hepatoid gland adenomas was considered as non-specific just as both glial fibrillary acidic protein in sebaceous gland tumours and hepatoid gland adenomas, and also S100 protein in sebaceous adenomas. All the examined tumours showed lack of expression of both desmin and factor FVIII. Thus, among the used antibodies, cytokeratins, vimentin, NSE, and α-SMA play a main role in the evaluation of canine adnexal histogenesis.