Air cyst of the maxillary sinus (pneumosinus dilatans, pneumocoele).

A cystic dilatation of a paranasal sinus by an entrapped air mass has been termed pneumosinus dilatans or a pneumocoele. The occurrence of this condition in the maxillary sinus is quite rare. In the present case, a mid-face mass mimicking an osteoma was the presenting sign of the disease. The pathogenesis, clinical features and radiological aspects of this entity are reviewed. In order to avoid confusion with other conditions of different aetiopathogenesis, we propose to label the lesion as 'air cyst' of the paranasal sinus, a term that best describes the nature of the lesion.