Page 400 - Concise Pathology for Exam Preparation ( PDFDrive )

14 The Oral Cavity and Gastrointestinal Tract 385

Precancerous Lesions

The most relevant precancerous lesions are
Leukoplakia
The term leukoplakia is defined by the World Health Organization (WHO) as, ‘a white patch/
plaque that cannot be scraped off and cannot be characterized clinically or pathologically’.
Approximately, 5–25% of these lesions are premalignant. Thus, until proved otherwise by
histological evaluation, all leukoplakic patches must be considered precancerous.
Differential diagnosis of white lesions in the oral cavity:
• Reactive epithelial hyperplasias (hyperorthokeratosis, parakeratosis and acanthosis)
• Leukoplakia of infective origin (candida, syphilis and hairy leukoplakia associated with
Epstein–Barr virus)
• Lichen planus
• Oral submucous fibrosis
• Lupus erythematosus
• Congenital lesions (eg, white sponge nevus, dyskeratosis congenita and pachyonychia
congenita)
• Invasive carcinoma
Morphology
• Leukoplakic patches are mostly seen on the cheek (buccal) mucosa, angles and floor of
the mouth, tongue, palate and gingiva.
• They may be solitary or multiple, and are of variable size and shape.
• Microscopic examination shows varied histopathology ranging from hyperkeratosis and/
or acanthosis without atypia to lesions with marked dysplasia, sometimes merging into
carcinoma in situ or invasive carcinoma.

Erythroplakia
• Erythroplakia indicates a red patch that is difficult to categorize clinically as any estab-
lished disease entity. It usually presents as, a well-defined, velvety, granular or nodular
lesion in the soft palate, floor of mouth, ventral surface of the tongue and retromolar area.
• Erythroplakia almost always presents with superficial erosions; epidermal thickening is
unusual.
• Histologically, these lesions are more aggressive compared with leukoplakic lesions and
show changes varying from dysplasia, carcinoma in situ, to frankly invasive carcinoma.
The red colour of the lesion is due to marked subepithelial inflammation and dilatation
of submucosal vessels.

Squamous Cell Carcinoma

Squamous cell carcinomas (SCCs) comprise almost 95% of cancers of the head and neck
(HNSCCs) and are most commonly located in the oral cavity.
Pathogenesis
• The pathogenesis of SCC is multifactorial; smoking and alcohol in excess, inherited
genomic instability, persistent irritation and human papilloma virus (HPV types 16,
18 and 33) infection are all implicated.
• Actinic radiation (sunlight), pipe smoking, chewing of betel and arecanuts are the
known predisposing factors.
• SCC evolves through a multistep process in which activation of oncogenes and inactivation
of tumour suppressor genes are simultaneously ongoing.
Morphology
• Oral SCC may present as an ulcertive, verrucous or nodular plaque-like lesion, often
seen developing in a pre-existing leukoplakic or erythroplakic lesion.
• It usually begins as a dysplastic lesion, which progresses to carcinoma in situ and then
invasive carcinoma.

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