PREMALIGNANT LESIONS IN ORAL CAVITY
Classification schemes for lesions of the oral cavity typically have used the clinical appearance of lesions to determine which are premalignant. (1) Leukoplakia and erythroplakia are two clinical lesions widely considered to be premalignant. However, using clinical features to classify lesions is difficult because they vary in appearance and are likely to be interpreted subjectively by the clinician. A histopathologic diagnosis is generally more indicative of premalignant change than clinically apparent alterations.
A State of the Science
Clinical Lesions Associated with Premalignancy
The term leukoplakia is sometimes used inappropriately to indicate a premalignant condition. In fact, the term describes a white plaque that does not rub off and cannot be clinically identified as another entity. Most cases of leukoplakia are a hyperkeratotic response to an irritant and are asymptomatic,
but about 20% of leukoplakic lesions show evidence of dysplasia or carcinoma at first clinical recognition.(1) However, some anatomic sites (floor of mouth and ventral tongue) have rates of dysplasia or carcinoma as high as 45%. There is no reliable correlation between clinical appearance and the histopathologic presence of dysplastic changes except that the possibility of epithelial
dysplasia increases in leukoplakic lesions with interspersed red areas. In one large study, (2) lesions with an erythroplakic component had a 23.4% malignant transformation rate, compared with a 6.5% rate for lesions that were homogeneous. The term erythroleukoplakia has been used to describe
leukoplakias with a red component.
An erythroplakia is a red lesion that cannot be classified as another entity. Far less common than leukoplakia, erythroplakia has a much greater probability (91%) of showing signs of dysplasia or malignancy at the time of diagnosis.(3) Such lesions have a flat, macular, velvety appearance and may be speckled with white spots representing foci of keratosis.
The premalignant or malignant potential of lichen planus is in dispute. Some believe that the occasional epithelial dysplasia or carcinoma found in patients with this relatively common lesion may be either coincidental or evidence that the initial diagnosis of lichen planus was erroneous.(4) It is frequently difficult to differentiate lichen planus from epithelial dysplasia; one study found that 24% of oral lichen planus cases had 5 of the 12 World Health Organization (WHO) diagnostic criteria for epithelial dysplasia, and only 6% had no histologic features suggestive of that disorder. (5) However, Oral Cancer Background Papers as many reports on lichen planus patients followed over time indicate a higher than expected rate of malignant transformation,(6) it is prudent practice to biopsy the lesion at the initial visit to confirm the diagnosis and to monitor it thereafter for clinical changes suggesting a premalignant or malignant change.
Premalignant changes arising in other oral lesions are uncommon. White lesions such as linea alba, leukoedema, and frictional keratosis are common in the oral cavity but have no propensity for malignant transformation. The health professional can usually identify them by patient history and clinical examination.
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