Teaching Case

A 40-year-old female patient came to our department for the recent onset of bleeding from the right inferior dental arch, gum pain and difficulty moving the tongue.

An orthopantomography performed elsewhere showed a multilocular radiolucency with sclerotic border at the right jaw with loss of tooth 48.
CT examination (Fig. 1) confirmed the presence of a cystic mass in the right mandible, affecting the posterior part of the body (from 45) and the first part of the ramus.
The lesion caused cancellous bone osteolysis, deformation of the cortical bone with mass effect on the lateral (compressing the masseter and pterygoid muscles) and medial (compressing the tongue) side.
Tooth 48 was completely encompassed by the mass.
At MRI (Fig. 2) it showed to be polycystic with fluid and parenchymatous components and signs of recent bleeding.
It was encapsulated and had regular margins with compression of adjacent structures (including the major salivary glands).
A biopsy was performed and the diagnosis was ameloblastoma.
The patient was treated with "curettage".
After six months follow up CT (Fig. 3) and MRI (Fig. 4) were performed and showed persistence of disease with slightly decreased diameter (40x23mm; previously 40x33), regular margins, decreased displacement of adjacent organs, and heterogeneous contrast enhancement.

Ameloblastoma (AB) is the second most common odontogenic neoplasm [1], representing 1% of all oral odontogenic epithelial tumours and 11% of all odontogenic ones. The incidence of AB is 1 in a million, mainly affecting people between 30 and 60 years of age, with no gender difference [2]. Its aetiology is unknown. In 80% of cases AB affects the mandible (70% of those affecting molars or mandible rami, 20% premolars, 10% canines), in the remaining cases AB affect the maxillary bone [3].
AB has a slow growth and it is normally benign, however, cases of malignant AB are described in the literature, mainly with lung metastases [4, 5].
Symptoms are non-specific: firm swelling, facial asymmetry (or deformity if severe), pain (if AB spread to soft tissue), mobility or displacement of teeth, bleeding, ulcers and periodontal disease. When the tumour increases its dimension, it leads to cortical bone thinning resulting in an "egg shell crackling" (crepitus) sign. The slow growth allows reactive bone formation, leading to deformity of the jaw. In the end AB may perforate the bone spreading to soft tissues [6].
To diagnose AB, imaging findings are essential: Orthopantomography and CT may detect a unilocular/multilocular radiolucency of the jaw with soap-bubble sign or honeycomb sign.
Imaging findings are useful to study the cortical bone, its thinning, dislocation and resorption of teeth.
MRI is essential to study the compression or infiltration of adjacent structures [7].
Histologically AB may be divided in [8]:
- Solid/multicystic type, the most common form, divided in follicular and plexiform type. The follicular one may have prevalence of either spindle, acanthomatous, granular, or basal cells. The plexiform type has prevalence of basal cells in anastomosing strands. Stroma often has cyst-like degeneration.
- Extra-osseous/peripheral type, with the same histological patterns of the previous one but in a different location.
- Desmoplastic type, with a large amount of stroma, compressing the odontogenic epithelial components.
- Unicystic type.
Recent molecular studies associated AB with overexpression of RAB31, a member of RAS oncogene family, calretinin [9], polymorphism of P53 [10] and PTCH1.
Treatment planning should consider tumour size, location, histopathology and clinical/radiographic findings.
Treatment is primarily surgical, including conservative surgery with curettage, tumour enucleation and cryosurgery. This option has a very high rate of recurrence (60-80%) probably because it may leave small islands of tumour within the bone [11]. Radical treatment includes marginal and segmental resections with safe margins to reduce recurrences.
In metastatic cases chemotherapy is the treatment of choice; encouraging results have been obtained with carboplatin-paclitaxel or doxorubicin-cisplatin [12].