**2. Clinical forms**

Tumors may appear in various forms of ulcers, prominent fungal masses, papillary, wart-like, white and red plaques, or a combination of both. Many primary

#### **Figure 1.**

*Verrucous leukoplakia in the right buccal surface of a 72-year-old woman.*

*Oral Cancer: Epidemiology, Prevention, Early Detection, and Treatment DOI: http://dx.doi.org/10.5772/intechopen.99236*

#### **Figure 3.**

*White reticular striae on the right cheek mucosa of a 52-year-old man with oral lichen planus.*

#### **Figure 4.**

*Multiple areas of erythroplakia with ulceration in the left buccal mucosa because of chronic traumatic ulcer from self-biting in a 53-year-old woman.*

cancers of the mouth are asymptomatic, while advanced lesions are often ulcerative and have prominent, hard margins. Pain is often absent in the later stages of the disease [8]. Potentially malignant oral epithelial lesions (PMOEL) are a group of oral diseases that may exist before the onset of oral squamous cell carcinoma (OSCC) and include a group of clinically oral mucosal lesions such as leukoplakia, erythroplakia, submucosal fibrosis, and lichen planus. However, most PMOELs do not progress to cancer (**Figures 1**–**5**) [10].
