Mucocoeles of the frontal and ethmoid sinuses

A MUCOCOELE of a paranasal sinus is an accumulation of mucoid secretion and desquamated epithelium within the sinus, with distension of its walls. The aetiology of this condition remains uncertain. Brown and Goodhill (i) distinguish between primary and secondary types. In the primary mucocoele a cyst forms from a goblet cell gland and may grow to such an extent as to expand the sinus. We have found multilocular mucocoeles on four occasions (one was infected, a pyocoele). Small cysts containing thin whitish fluid or thick mucus are occasionally seen within the inflamed hypertrophic mucosa removed during sinus operations. Skillern (2) has described these as mucoid or retention cysts. According to Schuknecht and Lindsay (3) the lining is a single layer of cuboidal epithelium. This histological appearance corresponds with that of mucocoeles, which are lined by low columnar epithelium or cuboidal epithelium with goblet cells resting on a connective tissue layer infiltrated with round cells. The secondary type of mucocoele is thought to result from obstruction of the sinus ostium by a fracture, a tumour (e.g. osteoma of the frontal sinus), or an inflammatory sinusitis with subsequent resolution of the infection and sterilization of the exudate. Tamari and O'Neil (4) postulate that a submucosal injury, either haemorrhagic or infectious, produces progressive elevation of the sinus mucosa by the accumulation of exudate beneath it, resulting in a mucocoele. On the basis of this theory it is difficult to understand why mucocoeles have a consistent epithelial lining.