Most depressed lesions are ulcers. An ulcer is a loss in continuity of the oral epithelium . Clinically, the center of the ulcer is often yellow to grey with a red periphery . Occasionally, a red center may be observed. Ulcers often result from the rupture of elevated lesions such as vesicle, bullae, pustules, and papules.
Some depressed lesions are the result of atrophy or scarring and have an intact epithelial surface.
Clinically, it is quite easy to determine if a lesion is depressed by looking at the lesion from different angles and relying on stereoscopic vision. Depressed lesions may be single or multiple. A single depressed lesion is one lesion of a particular morphology. Where more than one lesion of a particular morphology is present, they are multiple . Since descriptors of single and multiple lesions vary slightly, single lesions will be considered first .