Ossifying Fibroma in the Nasal Cavity of a 2-Year-Old Horse

SIMPLE SUMMARY: This article reports on the clinical features, diagnosis, and management of ossifying fibroma in the nasal cavity of a 2-year-old horse. Ossifying fibromas (OFs) are rare, benign, fibro-osseous neoplasms that occur more frequently in the rostral mandible of young horses (termed equine juvenile mandibular ossifying fibromas) but rarely in older horses. The occurrence of OF in young animals suggests developmental disorders or trauma as etiological factors. The local recurrence of OFs is common if they are not completely surgically excised, but metastatic spread is unusual. The presented case remained clinically asymptomatic until the mass obliterated the whole nasal cavity, causing severe breathing difficulties. The exact mass location was revealed using diagnostic images—namely, radiographs and computed tomography (CT) images. A concurrent problem of an underdeveloped and hypoplastic last premolar tooth of the maxilla was diagnosed. Because the mass was well-demarcated, the horse underwent standing surgery to remove the mass and the tooth. Histopathological diagnosis of ossifying fibroma was confirmed. The patient recovered uneventfully and remained free of disease at the 2-year postoperative follow-up. ABSTRACT: A 2-year-old mare of an unknown breed was referred to the clinic due to undetermined breathing difficulties. Physical examination revealed painless swelling rostral to the nasoincisive notch and a large, firm mass protruding from the left nostril. Radiographic examination of the head revealed a mass occupying the left nasal cavity and a displaced and hypoplastic last premolar of the left maxilla. The CT scan showed a well-demarcated heterogeneous mass measuring 22 × 9 × 5 cm (length × height × width) in the left nasal cavity attached to the roots of the displaced tooth and conchae. The surgery was performed on the standing horse. Firstly, due to the oblique position of the displaced tooth, the extraction was performed extra-orally through the trephination and repulsion of the maxillary bone. In the next step, a direct surgical approach was chosen for the caudal part of the mass via the osteotomy of the left nasal bone. The mass was bluntly separated from the conchae and removed through the nostril using Fergusson forceps. The histopathological characteristics of the mass led to the diagnosis of ossifying fibroma. The horse recovered completely in seven months, without recurrence after two years.