Trichoepithelioma of the skin in dogs

Abstract

The results of a histological study of skin trichothelioma in dogs are discussed; they allow studying the cellular origin of the tumor for subsequent interpretation of the results in the differential diagnosis of trichotheliomas with other epithelial neoplasms in animals. The neoplasm obtained as part of research was subjected to histological interpretation after preliminary formalinization, paraffinization, and hematoxylin and eosin staining. Trichothelioma is an organ-specific benign tumor of the skin appendages with pronounced differentiation towards hair follicles. In a survey study, the histological structure of the entire section was heterogeneous consisting of randomly arranged fibroepithelial complexes separated by slit-like lumens. The epithelial cysts were of various sizes and were filled with a dark brown, dense mass. The cysts are epithelial complexes without a stroma in the form of a concentric layer of squamous epithelium cells with keratinization in the center. The shape and size of the cysts depend on the degree of maturity of the tumor. One of the characteristic features of trichothelioma in dogs is the presence of structures similar to hair follicles. The follicles may contain hair stems or not. Around the hair follicles, there are clusters of large polygonal cells with light-colored cytoplasm resembling the cells of the outer root sheath of the hair follicle. Closer to the surface of the neoplasm, there are nodules of basaloid cells in the fibrous stroma with visible papillae, as well as small corneal cysts which indicates the dynamics of oncogenesis and tumor growth. Thus, the characteristic pattern of trichoepithelioma is the signs of cell differentiation towards hair follicles and the formation of hair structure. The formed structural fibroepithelial complexes are the main subunit which is oriented towards the presence of cellular formations resembling an incomplete hair follicle in the form of follicular buds.