MJDF Oral & Dental Pathology 2 — Questions and Answers
Question 1: What are the histological features of oral squamous cell carcinoma (OSCC)?
- Invasive islands of malignant squamous cells with nuclear pleomorphism, abnormal mitoses, and keratin pearl formation (Correct answer)
- Only surface epithelial changes without invasion
- Uniform cells without any atypia
- Dense inflammatory infiltrate without epithelial involvement
Correct answer: Invasive islands of malignant squamous cells with nuclear pleomorphism, abnormal mitoses, and keratin pearl formation
OSCC shows invasive nests of squamous epithelium with nuclear pleomorphism, hyperchromatism, abnormal mitoses, individual cell keratinisation, and keratin pearl formation in well-differentiated cases.
Question 2: What is the most common site for oral cancer in the UK?
- Lateral border of the tongue (Correct answer)
- Hard palate
- Labial mucosa
- Floor of mouth (second most common)
Correct answer: Lateral border of the tongue
The lateral border and ventral surface of the tongue is the most common site for oral squamous cell carcinoma in the UK, accounting for approximately one-third of all cases.
Question 3: What is the mechanism by which tobacco causes malignant transformation in oral epithelium?
- Nitrosamines and polycyclic aromatic hydrocarbons form DNA adducts, causing mutations in tumour suppressor genes (TP53) (Correct answer)
- Direct thermal injury only
- Nicotine acts as a mitogen only
- Tobacco increases salivary pH causing damage
Correct answer: Nitrosamines and polycyclic aromatic hydrocarbons form DNA adducts, causing mutations in tumour suppressor genes (TP53)
Carcinogens in tobacco (nitrosamines, PAHs) form covalent DNA adducts, leading to mutations — particularly in TP53 tumour suppressor gene — driving malignant transformation of oral epithelium.
Question 4: What percentage of leukoplakia undergoes malignant transformation?
- Approximately 1–3% (higher for homogeneous; higher in non-homogeneous/speckled types) (Correct answer)
- 50%
- Less than 0.1%
- 100% always become malignant
Correct answer: Approximately 1–3% (higher for homogeneous; higher in non-homogeneous/speckled types)
Overall, approximately 1–3% of leukoplakia cases undergo malignant transformation; non-homogeneous (speckled, nodular, verrucous) subtypes carry a higher risk than homogeneous leukoplakia.
Question 5: What is the significance of erythroplakia compared to leukoplakia?
- Much higher malignant transformation rate (>40%) and more likely to contain dysplasia at presentation (Correct answer)
- Lower risk than leukoplakia
- Same risk as leukoplakia
- Only occurs on the palate
Correct answer: Much higher malignant transformation rate (>40%) and more likely to contain dysplasia at presentation
Erythroplakia (red patch) carries a far higher rate of dysplasia or carcinoma in situ at presentation (>40–50%) than leukoplakia, making it a more serious potentially malignant disorder.
Question 6: What is the pathognomonic histological finding in Sjögren's syndrome on minor salivary gland biopsy?
- Focal lymphocytic sialadenitis with focus score ≥1 (≥50 lymphocytes per 4 mm²) (Correct answer)
- Diffuse fibrosis only
- Acinar cell destruction without inflammation
- Granulomatous inflammation
Correct answer: Focal lymphocytic sialadenitis with focus score ≥1 (≥50 lymphocytes per 4 mm²)
A focus score ≥1 on labial salivary gland biopsy (≥50 lymphocytes per 4 mm² aggregated around ducts/acini) is the histological hallmark and part of the diagnostic criteria for Sjögren's syndrome.
MJDF Oral & Dental Pathology 2
What are the histological features of oral squamous cell carcinoma (OSCC)?