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

This question checks which lesion among common odontogenic lesions grows into the jaw bone like a tumour, instead of staying as a simple cyst or a surface swelling.

1. Odontogenic myxoma: A benign tumour of the tooth forming connective tissue. It can expand the jaw but is not the classic example used for locally invasive behaviour.
2. Fibromatous epulis: A fibrous lump on the gum caused by ongoing irritation, such as from a denture or calculus. It sits on the surface and does not eat into bone.
3. Dentigerous cyst: A cyst that grows around the crown of a tooth that has not erupted. It enlarges the jaw slowly through fluid pressure, not through tumour cell invasion.
4. Ameloblastoma: A tumour of odontogenic epithelium. Even though it is called benign under the microscope, it grows in finger like extensions into the cancellous bone and comes back if not removed with a wide margin. This is why textbooks describe it as locally invasive.

The correct choice is ameloblastoma, since it is the one lesion on this list that is treated like a locally aggressive tumour rather than a cyst or a reactive growth.

Let's summarize:

• Cysts like the dentigerous cyst grow by fluid pressure, not by invading tissue.
• Ameloblastoma needs wide surgical margins because it invades bone locally, unlike the other options here.

So the odontome that is a locally invasive tumour is ameloblastoma.