Ethmoidal aneurysmal bone secondary to an ossifying fibroma

Case contributed by Dr Ian Bickle

Presentation

This boy presented to ENT with right sided nasal blockage and mild facial pain.

Patient Data

Age: 10 years old
Gender: Male

Large expansile bone based mass centred on the right ethmoidal sinuses, with a thin dense bony rim.

Mass effect on the right medial orbital wall.

The floor of the anterior cranial fossa is deficient.

The MRI showed a largely fluid filled mass, with a solid rim, again confirming mass effect on medial orbit wall, but no cortical breech.

Fluid in the right maxillary and sphenoid sinuses.

Several months later the patient returned to medical attention. A ENT procedure was performed in the interim for a presumed mucocele.

Modality: CT

The mass remains, albeit the more solid component is less evident.

The bony destruction has progressed with a 2cm in the planum sphenoide.

CT following previous ENT surgery.

Modality: MRI

Repeat MRI shows a very much different internal composition to the mass.

It now has multile fluid-fluid levels in, suggestive of haemorrhage of variable ages.

A stereolithographic model was produced for pre-operative planning.

The mass is coloured red. See the destruction of the anterior cranial fossa.

The pencil markings indicate the surgeons craniotomy approach.

Post-Operative CT

Modality: CT

The ethmoidal mass has been resected with reconstruction of the medial orbital wall and planum sphenoide.

The surgical approach planned on the stereolithographic model can be clearly matched with the operative result.

Histopathology

Modality: Pathology

Histopathological Report

Sections show parts of a well demarcated lesion composed of cellular fibrous tissue with a mineralised component. Components consist of small ossicles resembling psammoma bodies.

Other areas show pseudocystic spaces filled with blood and lined by macrophages with focal haemosiderin deposits and scattered multinucleate giant cells.

Comment: The appearances are in keeping with an ethmoidal aneurysmal bone cyst arising in conjunction with a residual juvenile psammomatoid ossifying fibroma.

Case Discussion

Sphenoid and ethmoidal masses are uncommon in children.

Aneurysmal bone cysts (ABC) may be primary or secondary, this this case secondary to a ethmoidal ossifying fibroma.

ABC's are typically located in the long bones, with less than 1% occurring in the skull.  Only a limited number have been described in the ethmoids.

ABC's are multi-cystic masses of non-endothelial line blood filled spaces, which gives rise to the characteristic appearances on imaging, in particular MRI, with a mass separated by thin septae, which contain fluid-fluid levels.  The levels representing blood of variable age, thus given different signal characteristics.

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Case Information

rID: 28717
Case created: 9th Apr 2014
Last edited: 8th Aug 2016
System: Head & Neck
Inclusion in quiz mode: Included

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