Journey of Leukoplakia So Far – An Insight on Shortcomings of Definitions and Classifications

Leukoplakia is one of the most frequently encountered white lesions by the clinicians. The definitions and terminologies associated with leukoplakia have been proposed by various authors. Also, various attempts have been made to clinically and histopathologically grade leukoplakia by evaluating different criteria. Although there are numerous reviews that have discussed the definitions and classifications of leukoplakia, none has attempted to provide a clear visualization of the shortcomings associated with each definition and classification. Hence, this review article is an attempt to highlight the main points as well as shortcomings in terminology, definitions, clinical classifications and histopathologic gradings which have been associated with leukoplakia till date.


Clinical classifications
Leukoplakia is one of the most commonly encountered white lesions by the clinicians and still holds an enigma around itself.Proper identification of the type of leukoplakia holds the key to successful treatment of the lesion.Hence, it is important for the clinician to recognize the type of leukoplakia as it can help in planning the treatment and also in predicting the malignant potential of the lesion [11].
Till date, numerous classifications for leukoplakia have been introduced based on criteria such as etiology, appearance, size and presence or absence of dysplastic features.Some authors have even commented, the clinical appearance of leukoplakia can be used to suspect the possibility of dysplasia being present in a lesion.Pindborg, et al. [12] confirmed that speckled leukoplakia was often associated with epithelial dysplasia or carcinoma as compared to homogenous leukoplakia.Sugar and Banoczy [13] in their three tiered clinical classification of 1969, reported that leukoplakia erosiva and leukoplakia verrucosa were more often associated with epithelial dysplasia than leukoplakia simplex.However, the clinical appearance cannot be confirmatively associated with presence or absence of dysplastic features.Various clinical classifications used for leukoplakia and their basis have been consolidated in Table 2 [14][15][16][17].

Introduction
The term "leuko" refers to white and "plakia" signifies a plaque/patch.Hence, the literal meaning of the term leukoplakia is a "white plaque".More than any other oral disease, leukoplakia has suffered from an excess of diagnostic terms and definitions; at least 75 have been used thus far.This has led to such mystification that many clinicians refuse to use any term beyond "white patch" [1].The first recorded white oral plaque/patch was an "ichthyosis" reported in 1818 by Alibert of Paris [2].
Although innumerous definitions and classifications have been devised, still there is a lack of consensus.The aim of this paper is to enlighten the highlights and shortcomings of these definitions and classifications.The knowledge and understanding of all the terminologies and classifications along with their shortcomings will provide a better insight for evaluating their appropriateness and comprehensiveness.

Terminologies and definitions
The first definitive terminology associated with leukoplakia was given by Schwimmer in 1877 [3].Since then, numerous changes have been introduced by authors pertaining to size, Schwimmer [3] (1877) First used the term "Leukoplakia" to describe a white lesion Clinical appearance *Homogeneous -A raised plaque of variable size which is predominantly white but can be grayish or yellow *Ulcerated -Red/yellowish area surrounded by white patches which appears like an ulcer *Nodular -A white patch on an erythematous base

*
Ebbing tide -Appears like indulations left on sand by an ebbing tide.Especially occurs on floor of the mouth *Others-All other types of appearances were grouped together *Inconclusive *Not commonly used Amagasa et al. [15] (1977) Clinical appearance *Type 1-Flat white patch/plaque without red components *Type 2-Flat white patch/plaque with erosion or red components *Type 3-Slightly raised or elevated white patch/plaque *Type 4-Markedly raised or elevated white patch/plaque Introduced the criteria of being flat or raised

Table 1 :
Terminologies and definitions associated with leukoplakia.
Bouquot JE [8] (1994)A chronic white mucosal macule which cannot be scraped off, cannot be given another specific diagnostic name and does not typically disappear with removal of known etiologic factors*Diagnostic definition *First definition in which leukoplakiawas mentioned as a precursor of malignancy Known etiologic factors not mentioned

Table 3 :
Histopathologic grading systems associated with leukoplakia.