Oral cancer pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]
Overview
Genes involved in the pathogenesis of oral cancer include tumor suppressor genes (TSGs), particularly in chromosomes 3, 9, 11, and 17.
Pathophysiology
- The pathophysiology of oral cancer involves inactivated tumor suppressor genes, P16, and TP53 and overexpressed oncogenes, PRAD1.[1]
- In western countries (eg, United Kingdom, United States, Australia) TP53 mutations are the most common molecular change that leads to oral squamous cell carcinoma.
- In eastern countries (eg, India, Southeast Asia), ras oncogenes is a more common cause of oral squamous cell carcinoma.
Pathology of squamous cell carcinoma of oral cavity
- Squamous cell carcinoma (SCC) tumors make up 95% of all oral cavity cancers.
- They are classified based on macroscopic or microscopic features.
- Macroscopic features of squamous cell carcinoma are:[2]
- Infiltrative – Cancer is growing into the deeper layers of the oral cavity.
- Exophytic – Cancer is growing outwards from the surface of the oral cavity.
- Verrucous – Cancer has a wart-like appearance.
- Ulcerated – Cancer appears as an open sore.
- Flat – Cancer appears as an abnormal area in the lining of the oral cavity.
- Microscopic features can be seen only with a microscope:
- Type of cells:
- Differentiation: The cancerous cells may be well differentiated (look like normal cells), moderately differentiated or poorly differentiated (do not look or act like normal cells).
- Keratinization: Keratin is a protein found in the hair, skin and some mucous membranes. It makes tissue tough.
- Type of cells:
- Keratinized SCC has more keratin in the tumor.
- Non-keratinized SCC has very little or no keratin in the tumor.
- Well-differentiated SCC is usually keratinized, while poorly differentiated SCC is non-keratinized.
- Invasion of the cancer into deeper layers and tissues, such as fat and muscle.
- Based on their microscopic features, squamous cell carcinomas are divided into 2 types:
- Classical or conventional SCC
- Variants of SCC
Pathology of classical or conventional SCC
- Most cancers of the oral cavity are classical or conventional squamous cell carcinoma.
- This type of SCC starts in the squamous epithelium that lines the oral cavity and occurs most often on the lower lip, tongue and floor of the mouth.
- The microscopic features of classical SCC include:
- Epithelial pearls
- These are circular layers of squamous cells around a collection of keratin (a tough fibrous protein) in the centre.
- Epithelial pearls
- Spread of cancer into deeper layers of the oral cavity
- The cancer starts in the squamous cells of the epithelium and invades the deeper layers of the oral cavity.
Pathology of variants of SCC
- These squamous cell carcinomas have distinct microscopic features that make them look and behave differently from classical SCC.
- Verrucous carcinoma
- These tumours make up less than 5% of all oral cavity tumours.
- They have a wart-like appearance and develop most often on the gums (gingiva), lining of the cheeks (buccal mucosa) and larynx.
- Verrucous carcinomas are low grade, slow growing and rarely spread.
- They are associated with the chronic use of snuff or chewing tobacco.
- Basaloid SCC
- This is a rare but aggressive subtype of squamous cell carcinoma.
- It is more common in men older than 60 years.
- Papillary SCC
- This is a rare subtype of squamous cell carcinoma that grows outward from the surface of the epithelium (exophytic).
- HPV infection may have a role in the development of this type of cancer.
- Spindle cell carcinoma (SpCC)
- This is an aggressive, rare variant of squamous cell carcinoma.
- These tumors contain a mixture of conventional squamous cell carcinoma and spindle cells that resemble a sarcoma.
It is also known as sarcomatoid carcinoma, pseudosarcoma, carcinosarcoma, pleomorphic carcinoma, metaplastic carcinoma, collision tumor and Lane tumor.
- Acantholytic SCC
- This is a rare variant of SCC in which the connections between the malignant squamous cells break down.
- This results in microscopic spaces in the tumour tissue, which appear like glands or vascular spaces.
- Adenosquamous carcinoma
- This is a very rare, aggressive type of squamous cell carcinoma.
- It looks like classical squamous cell carcinoma, but also has mucus-containing gland cells.
- Lymphoepithelial carcinoma
- This is a rare subtype of squamous cell carcinoma.
- The microscopic appearance is similar to undifferentiated nasopharyngeal carcinoma.
- It is also called undifferentiated carcinoma.
References
- ↑ Bonneville JF, Metzger J, Pertuiset B (1975). "Demonstration of cystic brain tumors by angiotomography". Neuroradiology. 9 (4): 183–6. PMID 1186964.
- ↑ "Canadian Cancer Society Oral cancer".