Desmoplastic ameloblastoma: a histological variant of ameloblastoma

Desmoplastic ameloblastoma: a histological variant of ameloblastoma

Desmoplastic ameloblastoma (DA) is a rare odontogenic neoplasm tumor which is a histological variant of ameloblastoma. In Desmoplastic ameloblastoma, the islands of ameloblastoma are surrounded and often compressed by a dense and sometimes hyalinised fibrous connective tissue. Although ameloblastomas are usually located in the mandible, this variant often occurs in the anterior maxilla.

Desmoplastic ameloblastoma is one of the six histopathological subtypes of ameloblastoma. The age and gender groups affected by desmoplastic are similar to those affected by the conventional ameloblastoma. It usually presents as a painless enlargement of the jaw. Owing to its deceptive radiological appearance as a mixed radiopaque–radiolucent lesion, it is often mistaken as a fibro-osseous lesion.

Desmoplastic ameloblastomas are rare, accounting for approximately 4–13% of ameloblastomas.1 Their radiographic appearance as a mixed radiolucent-radio-opaque lesion is commonly confused with fibro-osseous lesions as in the present case.

A painless swelling of the jaw bone represents the chief initial complaint. The size of the tumour varies between 1.0 and 8.5 cm in diameter.

Radiographic features

Radiographically, about 50% show a mottled, mixed radiolucency/radio-opacity with diffuse margins, suggesting a fibro-osseous lesion. Resorption of tooth roots and bone formation may occur. The ill-defined borders make high-resolution CT and MRI helpful in treatment planning.Similar clinical and radiographic presentations of the present case lead to an initial diagnosis of a fibro-osseous lesion.

Most desmoplastic ameloblastomas display occasional classic islands of follicular ameloblastoma among the predominant strands and cords. Studies have shown that desmoplastic ameloblastoma shows a tendency to recur.

Radiographically, it causes a mixed radiolucent-radiopaque lesion with a diffuse border, which indicates greater aggressiveness compared to other types of ameloblastoma.

The mixed radiologic view shows an infiltrative tumor pattern, and when desmoplastic ameloblastoma enters the marrow spaces, remnants of the original non-metaplastic or non-neoplastic bone are found in the tumor tissue. The infiltrative behavior of desmoplastic ameloblastoma explains one of the characteristic features of the tumor, its indefinite border.

Desmoplastic ameloblastoma also appears as a poorly defined, mixed, radiolucent-radiopaque lesion mimicking a benign fibro-osseous mass, especially on panoramic and periapical radiographs. Histologically, desmoplastic ameloblastoma appears as irregular odontogenic epithelial islets surrounded by a narrow area of ​​loose structured connective tissue embedded in the desmoplastic stroma.

Relapse

Reported 15.9% of desmoplastic ameloblastoma relapses after treatment with enucleation and / or curettage, with a mean relapse period of 36.9 months. Most of the reported DAs underwent resection, most likely due to poorly defined boundaries, indicating an infiltration process and aggressive biological behavior.

Demoplastic ameloblastoma clinical picture

Clinically, desmoplastic ameloblastoma may develop in all ages, however, people of the 4th and 5th decade are more prone to be affected. No gender predilection of Desmoplastic ameloblastoma has been reported. Usually the desmoplastic ameloblastoma variation is smaller in size than other types of ameloblastoma. Desmoplastic ameloblastoma occurs in the anterior or premolar regions of the jaws and there is not any difference in prevalence between the maxilla and mandible.

Studies have shown that 13% of the ameloblastomas are of the desmoplastic variety while according to Kishino the desmoplastic ameloblastoma accounts for about 5.3% of all ameloblastomas. This mixed radiographic appearance is due to osseous metaplasia within the dense fibrous septa that characterise the lesion, and not because of the tumour itself producing a mineralised product

Reactive osteogenesis may occur in desmoplastic variants. This makes it difficult to differentiate it from an adenomatoid odontogenic tumour, ameloblastic fibro-odontoma and odontoameloblastoma. It has been suggested that desmoplastic ameloblastoma is derived from the periodontal ligament tissues.

Concerning the biological behavior of Desmoplastic ameloblastoma, it is mentioned in the WHO classification of odontogenic tumors that Desmoplastic ameloblastoma, like unicystic ameloblastoma and peripheral ameloblastomas, possibly have a lower recurrence rate than other ameloblastomas.

Concerning the biological behavior of Desmoplastic ameloblastoma, it is mentioned in the WHO classification of odontogenic tumors that Desmoplastic ameloblastoma, like unicystic ameloblastoma and peripheral ameloblastomas, possibly have a lower recurrence rate than other ameloblastomas.

Desmoplastic ameloblastoma has a predilection to occur in the anterior region of the lower jaw.
It often mimics fibro-osseous lesions.
Desmoplastic ameloblastoma should be included in the list of differential diagnosis of a mixed radiolucent–radiopaque lesion.

Fine needle aspiration cytology may mislead to the diagnosis of a cystic lesion.
Biopsy is mandatory for confirmatory diagnosis.
Association of desmoplastic component in a hybrid tumour is not rare.


References

Den Tim


Practicing Dentistry for 20 years