Oral Frictional Hyperkeratosis Workup

Updated: Feb 19, 2021
  • Author: Jose Luis Tapia, DDS; Chief Editor: Jeff Burgess, DDS, MSD  more...
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Other Tests

In some cases, the clinical presentation of oral frictional keratosis mimics potentially malignant oral lesions and oral cancer. New optical visualization devices have been developed as an adjunctive aid to a conventional clinical examination for differentiating between benign and malignant mucosal disorders. [25] These optical devices include the use of autofluorescence, multispectral fluorescence and reflectance, diffused white light with acetic acid rinse, and chemiluminescence with acetic acid rinse. [26] At the present time, well-designed clinical trials are not available to confirm the value of these devices for improved specificity and sensitivity in a general patient population. [26]



The diagnosis of frictional hyperkeratinization is typically made based on a detailed clinical examination and the finding of an oral habit or some other agent that has produced the chronic, low-grade irritation of the mucosa. In patients in whom the clinical evidence for frictional keratosis is equivocal or the appearance of the lesion is atypical, a biopsy of the tissue is indicated.

Premalignant and malignant conditions of the oral cavity most often appear benign, and using the clinical history and examination findings alone does not ensure the precise histologic nature of any oral lesion. In most cases, removal of the chronic irritation reverses frictional keratosis in 1-3 weeks.

If any doubt exists concerning a particular lesion or if residual keratotic foci persist despite the removal of the causative factor, then a biopsy is indicated. Most often, this should be a conventional scalpel biopsy.

The use of exfoliative cytology for the collection of cells is not usually appropriate because the frictional keratosis lesion, by definition, shows increased keratin on the surface, which makes the harvesting of the intermediate layer and basal cells much more difficult.

A oral brush biopsy may be used; however, because the thick surface layer of keratin is a barrier, moderate pressure must be applied in order to ensure that an adequate sampling of basal cells is obtained

Important to note is that a definitive diagnosis cannot be obtained from an oral brush biopsy specimen. Only a scalpel biopsy can provide an accurate diagnosis of the white lesion in question.


Histologic Findings

The oral mucosa is lined by stratified squamous epithelium that exhibits topographical differences correlated with specific physical demands or a higher degree of specialization. For example, the epithelium lining the floor of the mouth, the ventral side of the tongue, the buccal mucosa, and the soft palate is usually nonkeratinized; however, the gingiva and hard palate are keratinized.

Frictional keratosis shows hyperkeratinization (either hyperorthokeratinization or hyperparakeratinization) and acanthosis as the main microscopic features of the surface epithelium (see images below).

Low-power view of stratified squamous epithelium w Low-power view of stratified squamous epithelium with marked hyperkeratinization, acanthosis, and a prominent granular cell layer. Courtesy of Catherine M. Flaitz, DDS and Alfredo Aguirre, DDS.
High-power view of the surface keratin layer and a High-power view of the surface keratin layer and a prominent granular cell layer. Courtesy of Catherine M. Flaitz, DDS and Alfredo Aguirre, DDS.

The epithelial surface may be smooth, corrugated, or ragged, with multiple keratin projections. Bacterial colonies are frequently found attached to the surface when it is irregular or shaggy. Often, a prominent granular cell layer is present. Occasionally, vacuolated cells can be seen in the upper spinous cell layer, especially in patients with cheek-biting keratosis. The underlying dense, fibrous connective tissue may demonstrate a patchy chronic inflammatory infiltrate. The terms focal keratosis or focal hyperkeratosis are frequently used for the histopathologic diagnosis. Frictional keratosis is a clinical term that conveys the cause and effect of the condition.