An unusual mucinous osteoma with features of an ossifying fibroma in the nasal cavity of a horse.

This study revolves around a 4-month-old horse which showed facial distortion and abnormal respiratory noise. Post-examination, it was found that the horse had a rare type of bone tumour, termed as mucinous osteoma with ossifying fibroma-like properties, in its nasal cavity.

Case Presentation

• The case involves a 4-month-old Warm-blooded colt which was showing signs of facial distortion and an unusual respiratory noise that had persisted over two weeks. These symptoms prompted a clinical examination.

Clinical Examination

• Upon endoscopic examination and CT scan, a proliferative mass was found in the nasal cavity of the horse. The possible causes deduced from this clinical evidence were cyst formation of the concha, malformation, or neoplasia.

Post-Mortem Examination

• Euthanasia was performed, followed by a post-mortem examination of the horse. The examination revealed a well-delineated, semi-solid, jelly-like mass measuring 14.5 x 9.0 x 12.0 cm, in the horse’s left posterior nasal cavity, an anomaly that extended into the left frontal and maxillary sinus.

Microscopic Examination

• On examining the mass under a microscope, it was found that the mass was made up of interweaved bone trabeculae, regional lamellar bone, and fibroblast proliferation in a moderate fibro-vascular stroma. It was also noted that there was an abundant production of mucus in areas where there were signs of fibroblast differentiation.
• Some sections of the mass also contained irregularly shaped spicules of osteoid, encased by osteoblasts and scattered within a moderately vascularized, fibro-osseous stroma.

Diagnosis

• Based on the nature and features of the mass observed clinically and histopathologically, it was inferred that the horse was affected by a nasal mucinous osteoma, with features indicative of ossifying fibroma-like structures.