Ossifying fibroma of the tibia in a dog: A rare case of appendicular fibro‐osseous lesion

This report describes a 21‐month‐old male Cocker Spaniel crossbreed that presented for evaluation of chronic left pelvic limb lameness with an associated mass on the left tibia. Orthopaedic examination identified discomfort on palpation of the mass. Initial investigations, including radiographs and tru‐cut biopsies, were compatible with a non‐neoplastic bone proliferation. Following 6 weeks of conservative management, repeat radiographs and computed tomography imaging were compatible with progression of the lesion. The dog subsequently underwent an excisional biopsy, and histopathological examination confirmed a fibro‐osseous proliferation most consistent with ossifying fibroma. Five months postoperatively, a fissure fracture developed, and by 8.5 months, the lesion had progressed, prompting amputation of the affected limb. Histopathology of the amputated limb confirmed ossifying fibroma. The dog recovered fully and adapted well to three‐legged ambulation, with no signs of recurrence 16 months post‐surgery. To the authors’ knowledge, this represents the first reported case of tibial ossifying fibroma in a dog.