Ossifying lipoma.

Lipomata are the most common benign tumour of the head and neck. They may undergo a variety of changes, one of which is ossification which, although rarely seen, has a characteristic radiographic appearance. We present a case of a retropharyngeal lipoma which demonstrates ossification and discuss the features which differentiate this from an osseous lipoma. Current theories on the aetiology of lipomata and their ossification are reviewed.