Equine Case Study: Head Mass in a Juvenile Filly

Welcome to our equine case study: head mass in a juvenile filly. Continue reading to see the presentation, images, radiographic findings, differentials and conclusions. 

Presentation

A 5-month-old filly presented for investigation of a firm swelling over the right maxillary sinus in practice. She was otherwise well in herself. Radiographs were performed
to help diagnose the cause of the mass and sent to our team of equine radiologists for interpretation. This case report shows our findings and conclusions.

Radiographic findings

Radiographs revealed a large, markedly heterogenous expansile bone opacity mass over the right lateral and dorsolateral maxilla, and the caudal margin of the right incisive bone extending from the level of the interdental space between incisor and premolar teeth caudally to the level of the first molar tooth. The structure measured 14cm x 10cm x 8cm. The external surface of the structure was smooth in outline, with a thin cortex and without periosteal reaction. Internally, the structure had a mix of segmented rosette appearance and that of a ‘soap bubble’ texture. There is loss of normal definition to the nasal conchae and sinus margins, suggesting destruction of these structures due to mass expansion.

Conclusions

Figure 1:

Figure 1. Annotated oblique skull radiograph. A single large and expansile bone mass lesion within the right maxilla and incisive bones (red arrows). This structure has caused destruction of the roots of the 506, 507 and partially of the 508 (blue arrows).

Figure 2: Annotated dorsoventral skull radiograph. There is loss of normal structure to the right nasal passages, nasal conchae and the rostral portion of the paranasal sinus cavities (green arrows).

Differentials are:

• Juvenile ossifying fibroma (benign)
• Osteosarcoma
• Multiple ossifying fibromas
• Ameloblastoma
• Chondrosarcoma
• Fibrous dysplasia

Next steps

The diagnosis in this case was juvenile ossifying fibroma (benign). Our team of specialist equine radiologists recommended that a biopsy be taken to characterise the underlying aetiology. Computed tomography would be very useful to determine the extent of the mass should resection be considered, whilst endoscopic examination of the nasal and oral cavities is useful to assess integrity of the hard palate and soft tissues of the pharynx and larynx.