**4. Classification**

Various classification of premalignant laryngeal lesions have been given by various authors, still it continues to be a controversial topic of laryngeal pathology for decades now, considering the classification, histological diagnosis and the treatment aspect as well. For clinical management of these lesions system based on the evaluation of the grade of hyperplasia and/or dysplasia of epithelium have been established (**Table 2**).

According to Hellquist et al [21] a distinction can be made between various lesions:

• Grade I lesions, presenting hyperplasia and/or keratosis with or without mild dysplasia where stratification is preserved and superficial cellular layers show cytoplasmic differentiation.

The cellular and architectural atypia occur in the lower third part with nuclear crowding, cellular and nuclear pleomorphism with increased nuclear/cytoplasmic ratio.


This grading is based on the classification proposed by the Kleinsasser in 19631 and later, by Delemarre, distinguishing a first class characterized by simple squamous cell hyperplasia, a second class represented by squamous cell hyperplasia with atypia and third class represented by carcinoma in situ.

The modified Ljubljana [22, 23] classification, the modification done by a working group of European society of pathology in November 1997 in London, United Kingdom (UK) devised the classification to cater to specific clinical and histological laryngeal problems, as it does not follow the three grade criteria, so was divided it into four grades as follows:


#### *Premalignant Conditions of Larynx DOI: http://dx.doi.org/10.5772/intechopen.97870*

The term dysplasia was accepted in laryngeal pathology first after the Toronto Centennial Conference on Laryngeal Cancer in 1974, almost after 11 years of proposed Kleinsasser classification. Several terms such as squamous intraepithelial neoplasia (SIN) and laryngeal intraepithelial neoplasia (LIN) were introduced. The term squamous intraepithelial neoplasia (SIN) was used for laryngeal precursor lesions by Friedmann and Osborn in 1976, and 10 years later Crissman and Fu opted for intraepithelial neoplasia of the larynx [24]. In addition, Friedmann and Ferlito used laryngeal intraepithelial neoplasia (LIN) [25]. An attempt to reconcile different schemes showed:

1.LIN I is regarded the equivalent of mild dysplasia

2.LIN II of moderate dysplasia and

3.LIN III of severe dysplasia and carcinoma in situ.

After that many editions of the World Health Organization (WHO) classification have been proposed & all such terms like as squamous intraepithelial neoplasia (SIN) and laryngeal intraepithelial neoplasia (LIN) were used but are now being abandoned and replaced by squamous intraepithelial lesions (SIL) [26, 27]. The essential update in the four editions of WHO was the attempt to induce a simplification from a four- to a two-tier system. The current WHO classification (2017) thus recommends the use of a two-tier system with reasonably clear histopathological criteria for the two groups:

1.Low-grade and

2.High-grade dysplasia.

Although the disadvantages like inter observer variability apart, subjectivities and uncertainties still remains but to a lesser degree.

Hence, it is very difficult to predict accurately which lesions will progress into invasive malignancy based only on clinical appearance. The diagnosis, treatment and prognosis of these lesions depend almost entirely on their histological abnormalities. In **Table 3** we have compared the different classifications given by different authors.
