Question

Which one of the following odontomes is a locally invasive malignant tumour?

• A. Odontogenic myxoma
• B. Fibromatous epulis
• C. Dentigerous cyst
• D. Ameloblastoma

Hint:

Think of the odontogenic lesion that needs wide bone resection, not simple curettage.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question lists four lesions that arise from the tooth forming tissue (odontogenic lesions) and asks which one behaves as a locally invasive tumour rather than a simple cyst or a harmless overgrowth.

Step 2: Key Concept:
Among odontogenic lesions, most are either cysts (fluid filled sacs) or benign reactive growths that stay confined to one spot. Ameloblastoma is the one true exception. It is a benign tumour by cell type, but it grows in finger like projections into the surrounding jaw bone, so it behaves like a locally invasive tumour even though it almost never spreads to distant organs.

Step 3: Detailed Explanation:
Odontogenic myxoma is a benign tumour of the tooth forming mesenchyme. It can enlarge the jaw but grows slowly and is not the lesion classically labelled as locally invasive.
Fibromatous epulis is a reactive fibrous overgrowth of the gum, caused by chronic irritation. It stays on the gum surface and does not invade bone.
Dentigerous cyst is a fluid filled cyst that forms around the crown of an unerupted tooth. It can enlarge the jaw by slow pressure, but it is a cyst, not a tumour, and it does not invade surrounding tissue the way a tumour does.
Ameloblastoma arises from remnants of the dental lamina, the tissue that forms enamel. It grows as sheets and islands of cells that push into the cancellous bone of the jaw, destroying it locally. Because of this behaviour, surgeons treat it with a wide margin of normal bone, similar to how a malignant tumour is treated, even though true distant spread is rare.

Step 4: Final Answer:
The odontome that behaves as a locally invasive tumour is ameloblastoma.