**1. Introduction**

The location of larynx is quiet unique that is it lies at the crossroads of air and food passages often referred to as part of the upper aerodigestive tract. It is also known as the organ of phonation, owing to its anatomical evolution & ability to produce voice. Indeed, from a physiologic point of view, it is essentially a valve or sphincter with a triple function: that of an open valve in respiration; that of a partially closed valve whose orifice can be modulated in phonation; that of a closed valve, protecting the trachea and bronchial tree during deglutition [1].

The larynx commences at the laryngeal inlet, (consisting of epiglottis anteriorly, aryepiglottic folds on either sides and interarytenoid fold posteriorly) and extends to the inferior border of cricoid cartilage, lying opposite the 3rd to 6th cervical vertebrae in adults and is somewhat higher in children. Structurally, it can be divided into three subsites, namely, the supraglottis, glottis and the subglottis by true and false vocal folds.

There are certain areas of larynx which are difficult to visualize through routine outpatient procedures like indirect laryngoscopy and these areas are of great clinical importance since many a times tumors tend to involve these subsites and are missed due to their anatomical location. Hence these areas require a special mention when discussing the anatomy.

Anterior commissure (anterior convergence of vocal folds and its insertion into the laminae of thyroid cartilage) is difficult to visualize through indirect laryngoscopy, it is located at the anterior junction of the two vocal folds, many a times a residual tumor is left behind during the surgical management; and if not managed properly, causes notable post-op morbidity. Between the two arytenoid

#### *Pharynx - Diagnosis and Treatment*

cartilages is present the posterior commissure. The vocal folds extend anteriorly to form a concentration of collagen fibres, known as anterior commissure tendon or Broyle's ligament which is attached to the deep layer of lamina propria and the inner perichondrium of the thyroid cartilage. Broyle's ligament, being devoid of glands, is resistant to the spread of tumors and hence acts as an effective safety barrier for further spread of malignancy. On the other hand, the mucosa of the glottis, lying superior and inferior to this ligament, is thrown back on the bare areas of thyroid cartilage, which can gave way to malignancies to invade the thyroid cartilage.

Histologically, two types of mucosal linings can be seen in larynx. Most of it is lined by pseudostratified ciliated columnar (respiratory) epithelium, except the vocal folds, the posterior glottis, a part of aryepiglottic folds and half of posterior surface of epiglottis, which are lined by non-keratinizing stratified squamous epithelium. The transition between the two epithelia, marked by the inferior arcuate line (present on the upper surface of vocal folds), is a common site for squamous cell carcinoma in larynx. The mucous glands, though freely dispersed throughout the mucosa of the larynx, are exceptionally numerous on the posterior surface of epiglottis and in the saccule. The mucus from the glands in the saccule are responsible for the lubrication of the vocal folds [2].

The malignancy was recognized long back in ancient times but the concept of premalignancy was not introduced till the end of 19th century. The term premalignant/precancer was introduced by Dubreuilh in 1896 for skin lesion and during the same era Durant described the first documented cases of laryngeal leukoplakia as "white cicatrices" adjacent to a malignant laryngeal lesion [3]. Later after almost 4 decades Jackson in 1923 conceptulized premalignancy of larynx as similar to a "large no. of citizens leaving their regular daily routine & mobilizing preparatory to invasion" [4].

Laryngeal cancer is the most common cause of head neck cancer in United States of America & is responsible for thousands of death each year [5]. The best chance of curing any cancer is via its early detection and eradication as morbidity and mortality are proportionately related to stage. Thus, appropriate management of precancerous laryngeal lesions in those patients fortunate enough to present at this stage is obviously vital.

The premalignant lesions of larynx are the identifiable local features that with time has a tendency to transform into invasive carcinoma. This change in the local sign occurs basically due to changes in the laryngeal cell that may lead to dysplastic or hyperplastic epithelial changes. WHO (World Health Organization) has defined premalignant lesions of larynx as morphological alterations of the mucosa caused by chronic local irritative factors as referable to local expression of generalized illness, presenting a higher probability of degeneration into the carcinoma with respect to surrounding mucosa. Moreover, WHO has classified these lesions on the basis of hyperplasia & various degree of dysplastic changes into simple squamous cell hyperplasia, mild dysplasia, moderate dysplasia, severe dysplasia & carcinoma in situ [6].

The epidemiology of premalignant lesions, reveals a scarce data. However, it is known that these lesions are more prevalent in males and are frequently seen in patients above 50 years of age.

A wide array of conditions have been implicated in the development & rapid transformation of premalignant lesions into an invasive cancer, including long-term tobacco exposure and alcohol abuse, various occupational professions related to the textile industry, chemical industries dealing with wood processing. A small proportion of carcinomas appears to be related to transcriptionally active human papillomavirus infection. So these factors basically changes the morphology of the glottis epithelial cells into hyperplastic & dysplastic changes. To understand this we must know the normal epithelial spread of larynx (**Table 1**) (**Figures 1** and **2**).

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


**Table 1.** *Normal histology of larynx.*

#### **Figure 1.**

*Histological view of larynx (Nonkeratinized stratified squamous epithelium).*

#### **Figure 2.**

*Histological view of larynx (Pseudostratified ciliated columnar epithelium).*

Although we are concerned about premalignant lesion only but this is important to understand the possible histological variety of malignant neoplasms that may arise in the larynx (**Table 2**) reflecting the different tissues from which they


#### **Table 2.**

*Histological Subtypes of Laryngeal Malignancies and their variants.*

originate. The vast majority, however, are squamous carcinomas (up to 95%) and predominantly arise on the true vocal folds. All other histological subtypes will necessarily develop via a premalignant phase, but due to the paucity of such cases in the literature they have not been studied and characterized to the same extent as premalignant squamous carcinomatous lesions [7].

So it is the normal histological pattern which undergoes these various changes at the cellular & genetic level under the influence of various factors as already mentioned above, thus changes into a dysplastic or hyperplastic variation may occur, making it vulnerable to transform into a cancerous lesion.

The macroscopic changes of the lesions have no appearance & hence in clinical practice are commonly referred as: leukoplakia, erythroplakia, erythroleukoplakia, keratosis and chronic laryngitis although there is no consensus on this issue. The current laryngeal investigation systems for obtaining the high quality & resolution images so as to reveal the detailed morphology of glottis structures is one of the main task in laryngeal imaging & helps in diagnosis. These includes:


So the appearance of lesion with these mentioned investigation system is no doubt of great help in diagnosis & prognosis of lesion but histopathological appearance is always diagnostic.
