Mucocelr is commonly seen in sinus:

A mucocele is an epithelial lined,mucus containing sac completely filling the sinus and capable of expansion: Mucocele are most commonly formed in frontal sinus followed by Ethmoid,sphenoid and maxillary sinuses. Mucocele of frontal sinus presents as a swelking in the floor of frontal sinus above the inner canthus.Itbdisplaces the eyeball forward,downward and laterally. Ref Dhingra 6/e,p 198;Tuli 1/e,p 196.