MFDS Oral Pathology

Question 1

A radiolucent lesion is found at the apex of a non-vital lower premolar. Histological examination reveals a cyst lined by non-keratinised stratified squamous epithelium with arcading pattern and cholesterol clefts in the wall. What is the most likely diagnosis?

Accepted Answer

Radicular (periapical) cyst

Answer

A radicular cyst is the most common odontogenic cyst, arising from epithelial cell rests of Malassez stimulated by inflammation from a non-vital tooth. The characteristic histological features include non-keratinised stratified squamous epithelium with an arcading (net-like) pattern, and the cyst wall typically contains chronic inflammatory cells, cholesterol clefts surrounded by multinucleated giant cells, and haemosiderin deposits.

Question 2

Which odontogenic tumour is characterised by the histological appearance of ameloblast-like cells arranged in a follicular or plexiform pattern with stellate reticulum-like areas?

Accepted Answer

Ameloblastoma

Answer

Ameloblastoma is a locally aggressive benign odontogenic tumour that recapitulates the enamel organ. The follicular pattern shows islands of epithelium with peripheral tall columnar cells (resembling ameloblasts) showing reverse nuclear polarity, surrounding central areas of loosely arranged cells resembling stellate reticulum. The plexiform pattern shows anastomosing strands and sheets of epithelium. It most commonly occurs in the posterior mandible.

Question 3

What is the most common malignant tumour of the oral cavity?

Accepted Answer

Squamous cell carcinoma

Answer

Squamous cell carcinoma accounts for approximately 90% of all malignant tumours of the oral cavity. The most common sites are the lateral border of the tongue and the floor of the mouth. Major risk factors include tobacco use, alcohol consumption (synergistic effect), betel quid chewing, and HPV infection (particularly for oropharyngeal SCC). The TNM staging system is used for classification, and treatment typically involves surgery with or without adjuvant radiotherapy.

Question 4

A 12-year-old patient presents with a well-defined radiolucent area surrounding the crown of an unerupted lower second premolar. What is the most likely diagnosis?

Accepted Answer

Dentigerous (follicular) cyst

Answer

A dentigerous cyst is the second most common odontogenic cyst, developing from the reduced enamel epithelium and attached to the cemento-enamel junction of an unerupted tooth. It presents as a well-defined unilocular radiolucency surrounding the crown of an unerupted tooth, most commonly lower third molars, upper canines, and lower premolars. Treatment is enucleation with removal of the associated tooth, or marsupialization if the tooth may erupt.

Question 5

What are the histological features that distinguish an odontogenic keratocyst (OKC) from other odontogenic cysts?

Accepted Answer

Thin, regular parakeratinised stratified squamous epithelium (5-8 cells thick) with a corrugated surface, prominent basal layer with palisading, and absence of rete ridges

Answer

The OKC (now reclassified as odontogenic keratocyst in the 2017 WHO classification, reverting from 'keratocystic odontogenic tumour') has distinctive histology: a thin, regular parakeratinised stratified squamous epithelium typically 5-8 cells thick with a corrugated (wavy) surface, a well-defined palisaded basal layer of cuboidal or columnar cells, and characteristically lacks rete ridge formation. The lumen contains desquamated keratin. These features, along with its high recurrence rate, distinguish it from other odontogenic cysts.

MFDS Part 1 Practice Test

MFDS Part 1 Practice Test

MFDS Oral Pathology