Morsicatio mucosae oris--a chronic oral frictional keratosis, not a leukoplakia.

PURPOSE Morsicatio mucosae oris (MMO) presents as white papules and plaques that may resemble leukoplakia, and are often biopsied. The objective of this study is to document the clinical features and histopathology of MMO and to reevaluate the prevalence of dysplasia and/or cancer when this frictional keratosis is removed from the category of leukoplakia. MATERIALS AND METHODS Cases that were submitted to a single laboratory with a provisional diagnosis of "leukoplakia," "hyperkeratosis," or "white lesion" were evaluated. RESULTS Fifty-six lesions of MMO from 56 patients were identified out of 584 white lesions. Most cases occurred in the third to sixth decades of life. Thirty (53.6%) and 18 (32.1%) out of 56 lesions were located on the lateral tongue and buccal mucosa, respectively. The lesions showed hyperparakeratosis with a characteristic frayed, shaggy, peeling surface, and acanthosis with insignificant inflammation. When MMO is removed from the category of leukoplakia, the percentage of true leukoplakia that are dysplastic or malignant increased by 12.9%. CONCLUSIONS MMO is a form of chronic oral frictional keratosis that has no malignant potential, and should be signed out as such and not merely "hyperparakeratosis and acanthosis" so that it can be removed from the category of leukoplakia where it does not belong.