Rare calvarial ossifying fibroma controlled with surgery and VMAT

A new case report in Veterinary Radiology & Ultrasound details the successful management of a rare calvarial ossifying fibroma in a 6-year-old Boxer using partial surgical excision followed by definitive-intent volumetric modulated arc radiotherapy. The dog presented with periocular swelling, nasal discharge, and exophthalmos, and the authors report durable local control with no recurrence after more than one year. For a lesion type that is both uncommon and diagnostically tricky, the combination of unusual imaging findings and multimodal treatment is the real news hook. (onlinelibrary.wiley.com)

That matters because ossifying fibroma sits in a difficult diagnostic neighborhood. Veterinary literature has shown that benign proliferative fibro-osseous lesions, including ossifying fibroma and fibrous dysplasia, can overlap substantially on histopathology, while some lesions initially called ossifying fibroma are later reclassified as fibrous dysplasia or low-grade osteosarcoma once imaging is reviewed. In one often-cited series of canine oral fibro-osseous and osseous lesions, final diagnosis depended on combining imaging, pathology, and clinical context, with well-circumscribed margins favoring ossifying fibroma and ill-defined margins raising concern for fibrous dysplasia or malignancy. (journals.sagepub.com)

The skull location adds another layer. A 2023 report in the same journal described frontal sinus ossifying fibroma in a dog as the first published report at that site and only the second description of CT features of cranial ossifying fibroma in a dog, underscoring how sparse the literature remains for cranial presentations. More recently, a 2024 case report described surgical management of a zygomatic ossifying fibroma in a dog, again pointing to the rarity of these craniofacial lesions and the need for individualized planning. (onlinelibrary.wiley.com)

In the new Boxer case, the source abstract says partial excision was followed by definitive-intent VMAT, a highly conformal external-beam technique that can shape dose distributions tightly around complex targets while sparing nearby normal tissue. That’s especially relevant in skull cases, where the eyes, nasal passages, brain, and other critical structures can limit what surgeons and radiation oncologists can safely do. Veterinary radiation references describe definitive-intent treatment as the curative or longest-control approach, typically delivered in a planned course of fractionated therapy under specialty supervision. (onlinelibrary.wiley.com)

There doesn’t appear to be a separate press release or broad industry reaction attached to this case report, but the broader specialty context supports why the authors’ approach will draw interest. ACVR materials emphasize that radiation oncology training depends on advanced imaging, treatment planning, and longitudinal case management, and recent reviews in veterinary radiation oncology describe a broader shift from primarily palliative use toward more precise, curative-intent protocols, including IMRT and VMAT. Inference: this case fits that larger movement toward using advanced radiation planning for anatomically complex disease, even when the lesion is benign rather than overtly malignant. (acvr.org)

Why it matters: For general practitioners, surgeons, radiologists, and oncologists, the practical lesson is that “benign” doesn’t mean simple. A calvarial fibro-osseous lesion can produce significant clinical signs, may not be fully resectable without morbidity, and may be misclassified if imaging and pathology are interpreted in isolation. This report strengthens the case for multidisciplinary workup, including advanced imaging and specialist review, when a dog presents with expansile craniofacial bone disease. It also suggests that definitive radiotherapy may deserve more consideration after cytoreductive surgery in selected skull cases where local control, rather than metastatic risk, is the main challenge. (journals.sagepub.com)

There’s also a referral and communication angle. Pet parents facing a skull mass often hear a differential list that spans benign lesions, dysplastic processes, and malignant bone tumors. Cases like this one can help clinicians explain why diagnosis may evolve after imaging review and why referral to radiology, surgery, and radiation oncology may change the treatment plan meaningfully. Comparable skull tumor reports in dogs, including calvarial multilobular tumor of bone and other craniomaxillofacial neoplasms, show how local anatomy often drives outcomes and treatment selection. (pubmed.ncbi.nlm.nih.gov)

What to watch: The next question is whether this remains an instructive one-off or becomes part of a small but growing pattern, with future reports clarifying imaging hallmarks, margin expectations, radiation protocols, late effects, and the durability of local control beyond the one-year mark. (onlinelibrary.wiley.com)