Superficial mucoceles: pitfall in clinical and microscopic diagnosis.

Extravasation mucoceles can be so superficial that they are seen as subepithelial blisters. These may rupture and cause superficial painful ulcers, which usually heal quickly. Occasionally such lesions may be seen in association with other mucosal disorders, particularly lichen planus, and a biopsy is undertaken to establish the diagnosis. In addition, the reporting pathologist may make an erroneous diagnosis of a subepithelial vesiculating disorder such as mucous membrane pemphigoid, especially when the clinical history is vague. Eight cases are described that illustrate some of the pitfalls in clinical and microscopical diagnosis of superficial mucoceles.