Fibro-osseous lesions involving the paranasal sinuses, the mid-face and anterior skull base are uncommon. In addition, there appears to be no clear pathological or clinical classification that embraces the variety of lesions that exhibit such diverse pathological and clinical behaviour, yet may still be referred to as a fibro-osseous lesion. The diagnosis of fibrous dysplasia and ossifying fibroma is made on a combination of clinical, radiological and pathological criteria.

This paper emphasizes the clinical and pathological differences between fibrous dysplasia and ossifying fibroma. The more aggressive clinical behaviour of the latter is highlighted and a more radical surgical approach i s recommended. In contradistinction, fibrous dysplasia can exhibit a more benign behaviour and radical surgery s i not always justified.

A clinicopathological distinction between these two conditions is important from a management perspective despite the fact that they both may be encompassed under the ‘umbrella’ term fibro-osseous lesion.

Monostotic fibrous dysplasia of the temporal bone is a rare disease entity that may lead to progressive stenosis of the external auditory canal with resultant trapping of skin and the development of cholesteatoma. The cholesteatoma may extend widely into the temporal bone. Once cholesteatoma occupies the petrous apex, erosion out of the temporal bone can occur superiorly into the middle fossa, posteriorly into the posterior fossa, inferiorly into the neck, and infero-medially into the parapharyngeal space. We present a case in which minimal symptoms were present despite a massive temporal bone fibrous dysplasia and cholesteatoma. Eventually, cholesteatoma eroded into the parapharyngeal space, leading to airway compromise. Late presentation occurred because the otic capsule was spared, there was no external skull deformity and there was slow inferior and medial growth that was well tolerated, until the development of a parapharyngeal space abscess.