A 1-year-old Thoroughbred filly with left bony facial distortion was diagnosed with a multilobar expansile mass within the caudal maxillary and frontal sinuses on computed tomography (CT). Typical findings associated with a sinus cyst, including expression of amber fluid from the mass and a thick lining that could be peeled from the sinus walls, were found on surgical exploration of the sinus under general anaesthesia. Histological examination of firm structures within the fluid-filled cyst contained all components of embryologically normal dental tissue. The filly recovered well and entered training to race as a 2-year-old, as remodelling of the bony distortion and narrowing of the nasal passage was sufficient for airflow. Previous reports of paranasal cystic lesions in horses suggest developmental abnormalities as a causative factor, especially in young horses. Furthermore, heterotopic polydontia is reported as the underlying aetiology in some human paranasal sinus cysts. While polydontia has been reported in the paranasal sinuses and nasal passages of horses, this is the first case report that finds them associated with a cystic lesion within the paranasal sinus.

中文翻译：

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异位多牙症是纯种母马鼻窦囊性病变的原因

计算机断层扫描 (CT) 诊断出一头 1 岁纯种雌马左侧骨性面部畸形，在上颌尾部和额窦内发现多叶膨胀性肿块。在全身麻醉下对鼻窦进行手术探查时发现了与鼻窦囊肿相关的典型表现，包括从肿块中表达出琥珀色液体和可以从鼻窦壁上剥离的厚衬里。充满液体的囊肿内坚固结构的组织学检查包含胚胎正常牙齿组织的所有成分。小母马恢复良好，并在 2 岁的时候参加了比赛，因为骨骼变形和鼻道变窄的重塑足以让气流流动。先前关于马鼻旁囊性病变的报告表明发育异常是一个致病因素，尤其是年轻的马。此外，异位多牙症被报告为一些人类鼻窦囊肿的潜在病因。虽然在马的鼻窦和鼻道中已经报道了多牙菌，但这是第一个发现它们与鼻旁窦内的囊性病变相关的病例报告。