Trichoepithelioma in a Chick African Grey-Parrot (Psittacus Erithacus): Surgical Approach and Histomorphological Evaluation

Despite that feather folliculoma, a benign tumor of the feather follicle, is common in canary and budgerigar, trichoepithelioma, a similar benign follicle tumor, has never been reported in birds. A 3-month-old African grey parrot (Psittacus erithacus) was presented for evaluation of a cutaneous mass on the head. After a full clinical examination, a Computed Tomography showed a soft tissue, rounded mildly isodense mass at the level of the frontal bones, without bone involvement. The neoformation was excised using a CO2 laser and sent to the Laboratory for a comprehensive histological examination. Immunohistochemistry was also performed to well characterize the neoplasm, using PCK, CD10 and Vimentin. Vimentin was used to evaluated the positivity of tumoral stroma / dermal fibroblasts and to evaluate the co-expression in CD10 positive parabasal stromal cells. PCK were used to demonstrate the expression in epithelial cells of proliferating phollicular epithelium, but not in stromal CD10 and vimentin positive cells. Positive immunohistochemistry for CD10 is helpful in differentiating trichoepitheliomas from basal cell carcinomas. In trichoepitheliomas CD10 stains the stromal cells but not the epithelial cells. Trichoepithelioma is a superficial dermal lesion. Horn cysts are the most characteristic histologic feature. Tumor consist of a fully keratinized center surrounded by basophilic cells that have the same appearance as the cells in the basal cell carcinoma, except that they tend to lack high-grade atypia and mitoses. A 2-year follow-up after surgery, there is no recurrence of the tumor. This is the first report of trichoepithelioma in a young psittacine bird.