MFDS Oral Pathology 2 — Questions and Answers
Question 1: What is the significance of epithelial dysplasia in a biopsy of an oral white patch, and which histological features indicate severe dysplasia?
- Dysplasia is a normal finding in oral epithelium and has no clinical significance
- Dysplasia indicates disordered epithelial maturation with potential for malignant transformation; severe dysplasia features include drop-shaped rete ridges, abnormal mitoses in the upper epithelium, loss of polarity, and marked nuclear pleomorphism extending into the upper third (Correct answer)
- Dysplasia refers to excessive keratinisation and is always benign
- Dysplasia only occurs in epithelium overlying malignant tumours
Correct answer: Dysplasia indicates disordered epithelial maturation with potential for malignant transformation; severe dysplasia features include drop-shaped rete ridges, abnormal mitoses in the upper epithelium, loss of polarity, and marked nuclear pleomorphism extending into the upper third
Epithelial dysplasia represents disordered cell maturation and is the most important predictor of malignant transformation in potentially malignant oral lesions. Features include architectural changes (irregular rete ridges, loss of normal maturation, bulbous drop-shaped rete processes) and cytological changes (nuclear pleomorphism, increased nuclear-cytoplasmic ratio, abnormal mitoses, loss of polarity). Severe dysplasia involves the full thickness of the epithelium and carries the highest transformation risk.
Question 2: A patient presents with multiple jaw cysts. Genetic testing reveals a mutation in the PTCH1 gene. What syndrome is this patient likely to have?
- Gardner syndrome
- Gorlin-Goltz syndrome (naevoid basal cell carcinoma syndrome) (Correct answer)
- Peutz-Jeghers syndrome
- McCune-Albright syndrome
Correct answer: Gorlin-Goltz syndrome (naevoid basal cell carcinoma syndrome)
Gorlin-Goltz syndrome (naevoid basal cell carcinoma syndrome) is an autosomal dominant condition caused by mutations in the PTCH1 tumour suppressor gene on chromosome 9q22. Features include multiple odontogenic keratocysts (often presenting in the first decade), multiple basal cell carcinomas (especially after puberty), skeletal anomalies (bifid ribs, spina bifida occulta), calcification of the falx cerebri, palmar/plantar pits, and medulloblastoma in childhood.
Question 3: What are the characteristic histological features of oral verrucous carcinoma?
- Poorly differentiated cells with frequent mitoses invading deeply into muscle
- A well-differentiated, exophytic, broad-based squamous neoplasm with a verrucous surface, pushing (rather than infiltrating) deep margins, minimal cytological atypia, and keratin-filled clefts (Correct answer)
- Basaloid cells arranged in nests with peripheral palisading
- Spindle cells with extensive areas of necrosis
Correct answer: A well-differentiated, exophytic, broad-based squamous neoplasm with a verrucous surface, pushing (rather than infiltrating) deep margins, minimal cytological atypia, and keratin-filled clefts
Verrucous carcinoma is a variant of well-differentiated squamous cell carcinoma with a verrucous (warty) exophytic growth pattern. Key histological features include broad, club-shaped rete ridges that push into the connective tissue with a well-defined deep margin (rather than irregular infiltration), minimal cytological atypia, and keratin-filled clefts ('church spire' keratinisation). Despite being locally destructive, it rarely metastasises. Diagnosis requires a deep biopsy to demonstrate the pushing margins.
Question 4: A biopsy from a gingival swelling in a 25-year-old female shows a proliferation of multinucleated giant cells in a vascular stroma. Serum calcium and parathyroid hormone levels are normal. What is the most likely diagnosis?
- Brown tumour of hyperparathyroidism
- Peripheral giant cell granuloma (Correct answer)
- Osteosarcoma
- Aneurysmal bone cyst
Correct answer: Peripheral giant cell granuloma
A peripheral giant cell granuloma (PGCG) is a reactive lesion arising exclusively from the gingiva or edentulous alveolar ridge. It contains numerous multinucleated giant cells (osteoclast-like) in a vascular connective tissue stroma with haemosiderin deposits. It is histologically indistinguishable from the central giant cell granuloma and the brown tumour of hyperparathyroidism, hence the importance of checking serum calcium and PTH levels to exclude hyperparathyroidism. Normal biochemistry confirms PGCG.
Question 5: What is the WHO classification of salivary gland tumours with regard to mucoepidermoid carcinoma, and what determines its grading?
- It is always classified as benign regardless of histological features
- It is the most common malignant salivary gland tumour, graded as low, intermediate, or high based on the proportion of cystic spaces, mucous cells, epidermoid cells, neural invasion, necrosis, and mitotic rate (Correct answer)
- It is classified as a benign tumour that never recurs
- It is always high-grade and requires radical surgery
Correct answer: It is the most common malignant salivary gland tumour, graded as low, intermediate, or high based on the proportion of cystic spaces, mucous cells, epidermoid cells, neural invasion, necrosis, and mitotic rate
Mucoepidermoid carcinoma is the most common malignant salivary gland tumour (and the most common salivary malignancy in children). It is graded into low, intermediate, and high grade based on histological features: low-grade tumours are predominantly cystic with abundant mucous cells; high-grade tumours are predominantly solid with epidermoid cells, frequent mitoses, neural invasion, and necrosis. Five-year survival ranges from >90% for low-grade to <50% for high-grade tumours.
Question 6: Which viral infection is most strongly associated with oral hairy leukoplakia, and on which part of the oral mucosa does it typically present?
- Human papillomavirus (HPV) on the palate
- Epstein-Barr virus (EBV) on the lateral borders of the tongue (Correct answer)
- Herpes simplex virus (HSV) on the lips
- Cytomegalovirus (CMV) on the gingiva
Correct answer: Epstein-Barr virus (EBV) on the lateral borders of the tongue
Oral hairy leukoplakia is caused by Epstein-Barr virus (EBV) replication within the epithelial cells of the tongue. It presents as white, corrugated, non-removable patches on the lateral borders of the tongue, often bilateral. It is strongly associated with immunosuppression, particularly HIV/AIDS (where it may be the presenting sign), but also occurs in other immunocompromised states. Histologically, it shows epithelial hyperplasia with a corrugated surface, koilocyte-like cells, and absence of inflammatory infiltrate.
MFDS Oral Pathology 2
What is the significance of epithelial dysplasia in a biopsy of an oral white patch, and which histological features indicate severe dysplasia?