A Case of Malignant Trichoepithelioma (matrical Carcinoma) in a Cat: Pathomorphological and Immunohistochemical Findings

Malignant trichoepithelioma (MTE) or matrical carcinoma is a neoplastic change of matrical and inner root sheet cells. It is generally described in dogs, with no sex predisposition. In this case, a glassy skin mass was taken from a 8-year-old, female mixed breed cat. Histopathologically, it was presented with the typical matrical cells islands, central keratinisation and necrosis, hyalinated collagens, ghost cells and trichohyaline granules. Masson’s trichrome stain differentiated epithelial cells from connective tissue in the subcutis. Immunohistochemistry (ABC immunperoxidase method) revealed the malignancy of matrical cells. The Ki67 marker was especially helpful to show the malignancy potential of cells. The Her2neu marker, one of epidermal growth factors, reacted to invasive cells located at the periphery of islands. Connexin 43 was usefull to show loss of connection in malignant cells. Due to the less frequent occurrence and unusual localisation of MTE, the described case aimed at revealing microscopical and immunohistochemical findings by using potential markers of MTE tumours in the skin of cats.