A Guide to Clinical Differential Diagnosis of Oral Mucosal Lesions
Part II: Surface Lesions of Oral Mucosa

Remember that surface lesions of oral mucosa consist of lesions that involve the epithelium and/or superficial connective tissue. They do not exceed 2-3 mm in thickness. Clinically, surface lesions are flat or slightly thickened rather than being swellings or enlargements.

We initially divide surface lesions into three categories based on their clinical appearance: white, pigmented, and vesicular-ulcerated-erythematous.

White Surface Lesions of Oral Mucosa

Surface lesions of oral mucosa that appear white, tan, or light yellow are divided into three groups based on their clinical features:

1. White lesions due to epithelial thickening
2. White lesions due to accumulation of necrotic debris on the mucosal surface
3. White lesions due to subepithelial changes in the connective tissue.

Epithelial thickening white lesions appear white because the pink to red color of the blood vessels in the underlying connective tissue is masked by the increased thickness of the epithelium. These lesions are asymptomatic, rough to palpation, and cannot be rubbed off with a gauze. They appear flat white when dried.

Three of the epithelial thickening white lesions occur on the tongue: hairy tongue, hairy leukoplakia, and geographic tongue (erythema migrans).

Hairy leukoplakia is caused by Epstein-Barr virus and presents as unilateral or bilateral, asymptomatic, white, rough patches, usually on the lateral surfaces of the tongue. It most commonly occurs in HIV positive patients but can also be found in any immunocompromised patient. Hairy leukoplakia does not require treatment, but it should alert the clinician that the patient is immunocompromised.