Precursor Lesions of the Oral Cavity Cancer

There is a sequence of disease progression from:
- Atypia / dysplasia, to in situ carcinoma, to invasive cancer
Leukoplakia and erythroplakia:
- Are terms given to clinically identifiable lesions:
  - That may harbor invasive cancer or undergo malignant transformation
Precursor lesions may present as:
- Small patches or as a large verrucous plaques
- The surface can be:
  - Brown to red (erythroplakia) or may have circumscribed whitish plaques (leukoplakia)
  - White spots may ulcerate
Leukoplakia:
- Develops as a result of chronic irritation of the mucous membranes by carcinogens
  - This irritation stimulates proliferation of epithelial and connective tissue
- Histopathologic examination reveals:
  - Underlying hyperkeratosis associated with epithelial hyperplasia
- In the absence of underlying dysplasia:
  - Leukoplakia rarely (less than 5 %) is associated with progression to malignancy (Ridge, 2013; Massano et al., 2006; Thompson, 2003)
Erythroplakia:
- Red spots, friable adjacent normal mucosa:
  - Characterize erythroplakia
- It is associated with underlying epithelial dysplasia and has a much greater potential for malignancy than leukoplakia:
  - Carcinoma is found in nearly 40 % of the cases of erythroplakia (Ridge, 2013)
The classification of the world health organization (WHO) of precursor lesions is as follows (Barnes, 2005):
- Squamous cell hyperplasia:
  - Hyperplasia describes an increase in the number of cells:
    - This can be in the spinous layer (acanthosis), and / or in the layers of basal / parabasal cells (progenitor compartment) called basal cell hyperplasia
- Dysplasia:
  - Is characterized by cellular atypia, loss of normal cellular maturation, and loss of epithelial stratification:
    - Mild dysplasia:
      - Squamous intraepithelial neoplasia 1
    - Moderate dysplasia:
      - Squamous intraepithelial neoplasia 2
    - Severe dysplasia or carcinoma in situ:
      - Squamous intraepithelial neoplasia 3
  - The probability of developing a carcinoma depends on the degree of dysplasia:
    - In the case of severe dysplasia:
      - In the case of severe dysplasia:
        Up to 24% of patients may have an occult invasive squamous cell cancer (Ridge, 2013)