**2. Pathogenesis of head and neck cancer**

There is a prolonged preclinical phase for head and neck cancer, and also it constitutes welldocumented precancerous lesions. The precancerous lesions comprise leukoplakia, erythroplakia, oral submucous fibrosis (OSMF), lichen planus, and chronic traumatic ulcers. The frequency at annual rate was estimated to be in the range from 0.13 to 2.2% during the transformation of oral precancerous lesions to cancer [7, 8].

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

reverse smoking, will be acquired with palatal lesions resulting in white or mixed reddish-

Introductory Chapter: Head and Neck Cancer http://dx.doi.org/10.5772/intechopen.86272 3

A higher risk of malignant alteration may be related with the factors like female gender, lesions of long period, large precancerous lesions, precancerous lesions in nonusers of tobacco, tongue, and floor of mouth lesions, nonhomogeneous lesions, and lesions showing epithelial dysplasia and aneuploidy [11]. However, during the follow-up in patients, it is impossible to predict with certainty where the precancerous lesion will become malignant. The malignant alteration of precancerous lesions can be prevented by interventions, such as avoiding the use

WHO conveyed that head and neck cancer occurrence and death are high in India, Papua New Guinea, and Taiwan, China, where the habit of chewing betel quid's with tobacco or without tobacco or areca nut chewing is common, as well as in France, Eastern Europe, and parts of South America such as Brazil and Uruguay, where tobacco smoking and alcohol ingestion are high. The age-standardized incidence rates for men are, on average, twice as high as those for women. WHO reported that in selected countries where some reliable cancer registries exist, India is highest and Belarus is lowest, with incidence rates changing by more than five times in men and women. The estimated age-standardized incidence rates of head

In South and Southeast Asia, buccal (cheek) mucosa is the most common site for head and neck cancer; the tongue is the most prominent site in all other regions [12]. Regional differences in frequency and the site of occurrence are related to the major causes, which are betel quid and tobacco chewing in South and Southeast Asia and alcohol and smoking in Western countries [13]. The mortality rates of head and neck cancer range between 1 and 15 per 100,000 persons in different regions; mortality rates exceed 10 per 100,000 in Eastern European countries, such as the Czech Republic, Hungary, and the Slovak Republic. Head and neck cancer mortality rates are influenced by head and neck cancer incidence, access to treatment, and deviations in site distribution.

The trends in incidence and mortality among men and women are closely correlated with the patterns and trends in tobacco and alcohol use. Increase in tobacco and areca nut chewing and alcohol consumption causes an elevated incidence rate which has been reported in Karachi [14] and in Taiwan [15]. Head and neck cancer incidence and mortality rates have been gradually falling over the past 2 decades because of declining smoking prevalence and alcohol ingestion in the US [16]. However, because of human papillomavirus (HPV), there is an increase in cancers at the base of the tongue, which has been observed in white men in the United States [17]. It was reported that over the past 2 decades, incidence and mortality rates for head and neck cancer have been declining steadily in most European countries. The increasing rates had been observed in some Central European countries, such as Hungary and the Slovak Republic, reflecting changes in alcohol and tobacco consumption [18]. There was a steady

of tobacco and consuming alcohol and by excision of the lesions in selected cases.

and neck cancer also fluctuate among countries in different regions [6].

white lesions of the palate [10].

**3. Incidence and mortality**

**Figure 1.** Head and Neck Cancer Regions.

The clinical conditions such as nodular lesions, painless small ulcers, or growths present in very early preclinical invasive early stage cancers culminate the disease. Changes can be easily seen and are clinically detectable through careful visual inspection, and palpation of the oral mucosa was the hallmark of processes. Highlighting the disease prognosis that localized early head and neck cancers ˂4 cm that has not spread to the regional lymph nodes can be successfully treated with either radiotherapy or surgery resulting in 80% of 5-year survival rates [9].

Leukoplakia may be clinically categorized as homogeneous or nonhomogeneous condition, in which a white snowy plaque or patch will form on the tongue. If the lesions have a thin, flat, uniform, smooth, and white appearance, it is categorized as homogeneous, and nonhomogeneous lesions may have a white and red appearance or tiny, white, pinhead-size raised nodules on a reddish background or a proliferative, warty presence. Erythroplakia exists as a red patch with a smooth or granular surface that cannot be categorized clinically or pathologically as any other definable disease [10]. Erythroplakia has a higher chance than leukoplakia to anchorage occult invasive cancer and to undergo malignant transformation.

Interweaving white lines (known as *Wickham's striae*) with a reddish border or as a mix of reddish and ulcerated areas will appear on oral lichen planus. OSMF, mostly restricted to the people of Indian subcontinent origin and in certain Pacific islands such as the Mariana Islands, presents with a blanching of the oral mucosa, burning sensation, and intolerance to spicy food. As the disease progresses, hardening and weaken of the oral and pharyngeal mucosa occur, leading to reduced mouth opening and difficulty in swallowing and speaking. Smokers who smoke with the lighted end of the tobacco product inside the mouth, known as reverse smoking, will be acquired with palatal lesions resulting in white or mixed reddishwhite lesions of the palate [10].

A higher risk of malignant alteration may be related with the factors like female gender, lesions of long period, large precancerous lesions, precancerous lesions in nonusers of tobacco, tongue, and floor of mouth lesions, nonhomogeneous lesions, and lesions showing epithelial dysplasia and aneuploidy [11]. However, during the follow-up in patients, it is impossible to predict with certainty where the precancerous lesion will become malignant. The malignant alteration of precancerous lesions can be prevented by interventions, such as avoiding the use of tobacco and consuming alcohol and by excision of the lesions in selected cases.
