JVD 2020 #1 Presentation, Diagnostic Imaging, and Clinical Outcome of Conventional Ameloblastoma in Dogs; Tjepkema

Question 1

What are the cytologic features of ameloblastomas?

Answer 1

Differentiated ameloblasts (cells that produce enamel) and/or enamel organ differentiation but do not induce differentiation of odontogenic mesenchyme (ie no induction of the dental papilla or tooth-like structures)

Question 2

Where is the ameloblastoma neoplastic epithelium assumed to arise from?

Answer 2

Previously quiescent remnants of odontogenic epithelium that remain within the periodontium.
For centrally located (within the jaw bone)- likely arise from rests of Malassez or other entraped/ectopic remnant of enamel organ.
For peripherally located (ie within gingiva) likely arise from rests of Serres

Question 3

What are the 4 biologic subtypes of ameloblastoma in humans?

Answer 3

Peripheral- least aggressive, no bone involvement
Desmoplastic (1 case in dog)
Unicystic- (not reported in animals)
Solid/multicystic- variants: follicular, plexiform and acanthomatous

Question 4

What was the mean/median age of dogs that had conventional ameloblastoma in the study?

Answer 4

8.9/9 years

Question 5

How did conventional ameloblastoma present clinically- appearance?

Answer 5

A mass causing focal swelling and expansion within the jaw. The tumors often had a smooth surface of intact gingiva and/or mucosa with occasional fluctuant and dark-purple-blue cystic areas.

Question 6

What was the most common area affected?

Answer 6

Maxilla (13/20) compared to 7/20 mandible. Most in the canine/premolar region

Question 7

In those cases with diagnostic imaging available, what were the key features noted?

Answer 7

Loculated intraosseous lesion
Cystic features- central radiolucency with corticated border 11/13 cases.
More often a multicystic/multilocular pattern on rad and CT
Jaw bone lysis in 4/6 CT studies
Mixed lytic/proliferative pattern
External tooth resorption
Contrast enhancement in all cases with CT

Question 8

Histopathology of canine conventional ameloblastoma

Answer 8

Neoplastic odontogenic epithelium without induction of odontogenic mesenchyme or formation of tooth structures.
Odontogenic epith. had recognizable ameloblast-like cell morphology: tall cuboidal to columnar layer of basal cells with palisaded nuclei in the apical cytoplasm
Histo patterns seen similar to humans: basal, plexiform and follicular

Question 9

What was the treatment and outcome for cases in the study?

Answer 9

Most had wide surgical excision (17/20) and none had regrowth.
Half had narrow margins <0.5cm on histo