Painless swelling of the lower lip.

A characteristic example of a mucocele has been presented. Clinicians should be aware that even though these lesions have a distinctive clinical appearance and react biologically in a fairly characteristic manner, they must be differentiated from benign and malignant neoplasms that appear and react clinically similar to mucous retention phenomenons. Microscopic examination of tissue from the lesion is the only definitive method to make this differentiation.