History: Horse, warmblood, 20 years, male
Diagnosis: Right nasal cavity and paranasal sinuses: Multiple sinus cysts with abundant granulation tissue, suppurative rhinitis / sinusitis and moderate left-sided deviation of the nasal septum
Description: The right nasal cavity and sinuses were filled and obstructed by a multilobulated, partially solid and partially cystic mass of white to reddish color and firm texture with multiple foci of yellowish, smooth secretion.
Comments: The horse presented with a 10 years history of therapeutic formalin injections in a clinically diagnosed ethmoid hematoma. Necropsy was performed because the animal died unexpectedly due to other reasons and revealed a large cystic mass in the right nasal cavity and paranasal sinuses with deviation of the nasal septum. Histologically, cysts were lined by a cuboidal to columnar ciliated epithelium and surrounded by large proliferations of granulation tissue interspersed with multiple foci of suppurative inflammation. However, findings characteristic of an ethmoid hematomaincluding hemorrhage, hemosiderosis or the presence of multinucleated giant cells were missing. Following ethmoid hematomas, sinus cysts are the second most common differential diagnosis in horses for a mass in the caudal portion of the nasal cavity.
Picture and authored by: Anja Meyer, Department of Veterinary Pathology, Freie Universität Berlin, Germany