Teaching Case

A 10-year-old patient with a personal history of strabismus surgery at the age of 2 years, presented with progressive limitation of upward eye movements and proptosis of the right eye. She does not report diplopia, blurred vision or pain.

CT shows a voluminous lesion of the frontoethmoidal recess, involving the superomedial rim of the right orbit, highly hyperdense with a ground glass pattern suggesting fibrous component and patchy focus of ossification (Figures 1a and 1b).

MR images evidence a dense lesion, highly hypointense on T1-weighted and on gradient echo-sequences, and iso-intense on T2-weighted images, compatible with a fibrous-calcified lesion.

The lesion presents well-defined borders, extending caudally to the right nostril. It causes insufflation of the medial wall of the right orbit with a small mass effect on the extrinsic eye muscles. It extends superiorly, imprinting the right frontal lobe, displacing the midline, and showing linear frontal dural enhancement, without vasogenic oedema and absence of restriction on diffusion-weighted images.

Dynamic study shows early enhancement with late washout (type III curve (Figures 2a, 2b, 2c, 2d, 2e and 2f).

Three months after resection of the lesion, the image-MR control performed reveals a regrowth of the small residual lesion, with characteristic multiple haemosiderin fluid-fluid levels (Figures 3a and 3b).

Background

Juvenile ossifying fibroma is a rare, non-cancerous tumour composed of fibrous and bony tissue, typically occurring in the craniofacial bones of young patients. It tends to behave aggressively locally and has a tendency to recur [1].

Based on the 2017 WHO classification, ossifying fibromas are categorised into three types: cemento-ossifying fibroma, juvenile trabecular ossifying fibroma, and juvenile psammomatoid ossifying fibroma [2].

Clinical Perspective

This tumour can grow quickly, leading to local damage and facial asymmetry. If the paranasal sinuses or orbital bones are affected, it can result in epistaxis, bulging of the eye, proptosis, and changes in vision [3].

Cases associated with aneurysmal bone cysts, another benign but progressively destructive lesion with fluid levels, have been described [4].

Imaging Perspective

Imaging techniques are essential to assess the tumour’s extent and its involvement with the bone.

The radiological appearance of the lesion in CT varies with its maturity, but most show well-defined areas of density mixed with some radiolucent zones (ground glass areas). They also exhibit clear radiographic borders, with marginal sclerosis and a thin cortex [5].

Typical findings on MRI include a low signal on T1-weighted and gradient-echo images, and isointensity on T2-weighted images. Fluid-fluid levels may be present, sometimes reflecting an aneurysmal bone cyst association. Typical homogeneous enhancement on T1 images with contrast is usually seen [6].

CT and MRI show similar fluid levels and lesion extent. However, CT better defines the borders and internal calcification, allowing for the distinction between the different subtypes, which MRI does not [7].

Microscopic examination shows a fibroblastic stroma with loose or dense cellularity and minimal collagen, containing spherical calcium clusters. These bony structures resemble psammomas but are often irregularly shaped and less organised [8].

Outcome

Treatment is recommended as for a locally aggressive neoplasm, due to its aggressive nature and the high recurrence rates. Surgical resection is the preferred treatment, followed by close radiological monitoring.

Radiotherapy is contraindicated because it can increase cancer risk and cause potentially long-term damage in children.

The long-term prognosis is favourable, as there have been no instances of malignant transformation or metastases reported [9].

Take Home Message

Although juvenile ossifying fibroma is not a malignant tumour, its aggressive nature and high recurrence rate necessitate accurate diagnosis, radical surgical treatment, and close radiological monitoring.

The association of aneurysmal bone cysts can be suspected in the presence of fluid-fluid levels.

All patient data have been completely anonymised throughout the entire manuscript and related files.