Teaching Case

A 16-year-old female presented to the maxillofacial department with a two-month history of increasing swelling to the left midface with associated left nasal obstruction and left epiphora. On examination, the swelling corresponded to a retained deciduous molar (ULE). ULE was promptly extracted, and the extensive underlying fibrous lesion was biopsied.

Orthopantomograph (OPT) imaging of the dentition showed an ectopic upper left second premolar (UL5) tooth surrounded by radiolucency with a subtle radio-dense border and displacement of surrounding teeth. Subsequent CT imaging of the facial bones showed a marked expansion of the left maxilla by a large, multiloculated lesion approximately 50mm in diameter. The lesion elevated the antral floor to the point of contact with the orbital floor, medially it abutted the nasal septum and laterally it displaced the buccal soft tissue. The lesion extended posteriorly to the infratemporal surface of the maxilla, which it potentially breached. The lesion also breached both buccal and palatal cortices of the left maxillary alveolar ridge and extended from the central incisor to third molar. The lesion surrounded the ectopic UL5, which was significantly medially displaced. The lesion also displaced the surrounding premolar and molar teeth with evidence of root resorption.

Background

Odontogenic Myxomas (OMs) are locally aggressive, benign neoplasms of the jaws accounting for 3%–8% of all odontogenic tumours [1,2]. They are commonly associated with unerupted teeth and, although no definitive evidence exists, likely arise from the mesenchymal portion of the dental papilla [3]. A 2018 study identified a 1:1.8 male-to-female ratio, averaging 34 years old at presentation [2].

Clinical Perspective

75% of OMs arise in the mandible. The rarer maxillary OMs usually present as a slow, painless swelling of the midface, frequently displacing or mobilising adjacent teeth. They can quickly invade the maxillary sinus and reach considerable size before they are detected [4,5]. Detailed 3D imaging is essential to determine the extension of the lesion and the structures it involves, to plan reconstructive surgery. Maxillary OMs are often locally aggressive, and able to invade small marrow spaces that may be clinically indistinguishable from normal bone [6].

Imaging Perspective

Maxillary OMs usually form in the premolar region, developing from unilocular to multilocular lesions as they grow [6]. Their internal structure is often described as a "tennis racket appearance" with thin, straight septae and poorly defined margins, and this can aid in narrowing the differential diagnosis. On MRI, the internal contents of OMs demonstrate characteristically high signal on T2 weighted sequences [5]. MRI was not utilised in this case as it was unlikely to change surgical planning.

Outcome

The mainstay treatment for OM is resection with a wide surgical margin; however, smaller OMs have been successfully treated with enucleation and curettage [7]. This more conservative approach carries a higher risk of recurrence of up to 30%, due to the invasive stroma of the tumour remaining undetected [8]. In the posterior maxilla, marginal clearance is challenging due to anatomical restrictions such as the orbit, and recurrence can result in scenarios where lesions become unresectable. This patient underwent resection and reconstruction with deep circumflex iliac artery (DCIA) flap, dental implants and polyetheretherketone (PEEK) orbital implant.

Take Home Message / Teaching Points

Maxillary OMs are locally aggressive lesions that can invade structures of the midface such as the maxillary sinus, orbit and nose. The tumour contents can permeate adjacent marrow spaces, resulting in high rates of recurrence. Clinicians must be aware of this and plan treatment margins accordingly. The radiology team must consider OM as a differential in cases of multiloculated lesions of the jaws, especially when straight "tennis racket" septations are present, and be aware of the best choice of imaging and relevant follow-up.

Written informed patient consent for publication has been obtained.