Author: Sanketh DS, MDS
“Leuko” stands for white and “plakia” for patch. Leukoplakia, classified as a potentially malignant disorder, is a white patch that cannot be rubbed of and cannot be clinically diagnosed as any other disease. It has had numerous definitions over the years since it was first defined. In 2005, WHO defined leukoplakia as “a white plaque of questionable risk having excluded (other) known diseases or disorders that carry no increased risk for cancer”.
The definition of leukoplakia is unusual in that the diagnosis is one of exclusion of other white lesions rather than depending on a definable appearance of the lesion. To make it easier to understand, lets say you have a patient with a suspicious white patch in the buccal mucosa. Since there are several other white lesions that look like leukoplakia, make sure it is not any other white lesion. Only after this, could you make a diagnosis of leukoplakia. Hence, it is a diagnosis of EXCLUSION!
Leukoplakia or any other white lesion for that matter, appear white because of the thickened surface keratin layer and the hyperplastic epithelium. This thickened abnormal keratin layer evenly reflects the visible light spectrum as opposed to being permeable to visible light and the red spectrum being reflected by the connective tissue. This clinically masks the vascularity (redness) of the underlying connective tissue making it appear white!
Most cases of leukoplakia are related to use of smoked or smokeless forms of tobacco, and may or may not regress on discontinuation of the habits. Other factors like alcohol, trauma and candida albicans have also been reported to cause leukoplakia although these associations are now being disputed. Leukoplakia with no known etiological cause has been termed idiopathic leukoplakia.
This lesion is the most common precancer and usually affects the middle aged and the older population with majority of patients older than 40 years. Worldwide prevalence of leukoplakia is believed to be around 2% and it increases with age. It was known to have a higher male predilection but is now seeing a shift with nearly equal number of women being affected.
Buccal mucosa, mandibular vestibule, gingiva and lateral borders of the tongue are most commonly affected. Other sites though rare include, lip, floor of mouth, retromolar trigone, palate, mandibular and maxillary alveolar ridges. The risk of malignant transformation however is increased in sites like the floor of mouth and the tongue as compared to the buccal mucosa.
Clinical appearance and types
Leukoplakia is classified as being homogenous and non-homogenous. Homogenous refers to the uniformity of the colour and the texture of the leukoplakic lesion while non-homogenous leukoplakia may have a red-white appearance or may have a uniform white appearance with an irregular texture manifesting with nodules/wart like projections and corrugations.
Homogenous leukoplakia in the early stages may be thin, flat or slightly elevated, grey-white in colour with fissures while the leukoplakia that has progressed could be a thicker white plaque with deep fissures. These lesions are well circumscribed with sharply demarcated borders.
If these homogenous lesions develop surface irregularities, they are called granular or nodular leukoplakias. They are called verrucous leukoplakias when they develop deep corrugations and wart like projections.
Leukoplakia may reveal red patches manifesting as a mixed red-white lesion, called erythro-leukoplakia or speckled leukoplakia.
A notable form of leukoplakia, called proliferative verrucous leukoplakia, appears in multiple sites, showing slow, persistent growth eventually becoming verrucous and exophytic with a high rate of recurrence even after treatment.
TREATMENT AND PROGNOSIS
The prognosis of leukoplakia depends on various factors and is generally considered bad if :
a) It manifests in females.
b) The lesion is present for a long duration.
c) The affected is a non-smoker.
d) Leukoplakia is located on the tongue or floor of the mouth.
e) The size is greater than 2 cm.
f) The lesion is non-homogenous.
In the absence of dysplasia, excision is not mandatory although the patient should be under continuous surveillance and evaluation every 6 months. Re-biopsy of suspicious areas should be done. The use of antioxidant nutrients like Vitamin A,C and E, beta carotene and diet high in antioxidants – fruits and vegetables are recommended.
Leukoplakia with mild dysplasia is managed according to its size and response to conservative measures like habit cessation. For moderate to severe dysplasias excision should be done if feasible, although there are several studies which report that surgical excision do not reduce the risk of recurrence or the patient developing carcinoma. Grafting procedures may be necessary after large excisions.
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