A case of ameloblastoma in domestic shorthair cat

Abstract

Background Solid masses such as ameloblastomas are not common in the sinuses of cats. Ameloblastoma is a slow-growing tumor of odontogenic epithelial origin that does not contain odontogenic ectomesenchyme. The tumor is non-metastatic but locally aggressive with a high risk of recurrence. Materials & Methods A 13 year-old domestic hypersalivating European shorthair cat was brought into the clinic repeatedly due to a swelling under the left eye, located at the cheekbone area, with purulent discharge. A large hard intraosseal/intrasinusal mass with invasion of underlying and surrounding anatomical structures (maxilla and cheekbone) was observed. After 2 months, radiological examination showed significant progression of bone lysis and decreased tissue density in both maxilla and cheekbone. Routine HE staining and immunohistochemical stainings for BRAF V600E and calretinin were performed.\ Results On HE examination there were sheets and cords of anastomosing odontogenic epithelial cells supported by fibrovascular connective tissue stroma. A peripheral palisading arrangement and reverse polarity, basilar epithelial cytoplasmic clearing of epithelial cells were observed. Also, non-basilar (central acanthocytes) epithelial connection by prominent intercellular bridges was noticed. The central cells were polygonal, with large, unevenly sized, round nuclei with a single nucleolus. Anisocytosis and anisokaryosis were mild. Variable keratinization with indistinct keratin pearls were seldom visible. The mitotic count per 10 hpf was 22 mitosis. The IHC results showed strong positivity for BRAF V600E in basilar and central acanthocytes. Calretinin was negative. Conclusion The final diagnosis was ameloblastoma and treatment with Zelboraf was started. Three days later animal died unexpectedly.