Reoccurrence of a paranasal osteoma following surgical removal in a 6-month-old Warmblood filly

A 6-month-old Warmblood filly presented for evaluation of a left sided unilateral mucopurulent discharge of 5 weeks' duration. Upper airway endoscopy revealed a large, smooth mass in the region of the ethmoturbinates. Dorso-ventral and lateral radiographs of the head revealed a large osseous mass in the left paranasal area. A biopsy was performed under general anaesthesia and an osteoma was diagnosed. A computed tomography (CT) examination was performed to guide surgical removal. Surgery was performed under general anaesthesia and a large mass was removed ~15 × 9 cm. A CT examination 3 months following surgery revealed three small areas of mineralisation. It was difficult to differentiate if these were areas of regrowth or portions of the original mass that were not entirely removed. A CT examination 8 months later revealed one of the areas had increased moderately in size. A second surgery was performed standing to remove the growth. A final CT 8 months later revealed no further evidence of a bone growth. This report describes the successful removal of an osteoma regrowth following initial surgical removal and, to the best of the authors’ knowledge, is the first to describe the reoccurrence of an osteoma after surgical intervention. It also describes a successful rhinotomy in the standing equine patient. This case highlights the importance of serial follow-up imaging after surgical removal as osteoma regrowth occurred in this case.