Keywords
Ameloblastoma - computed tomography - imaging of ameloblastoma - unicystic ameloblastoma
Introduction
Ameloblastoma is the most common benign odontogenic tumor accounting for approximately
1% of tumors and cysts of the jaw and 10% of all the odontogenic tumors.[1] It is a slow-growing, persistent, and locally aggressive neoplasm that may originate
from the epithelium involved with the formation of teeth such as enamel organ, odontogenic
rests of Malassez, reduced enamel epithelium, and odontogenic cyst lining.[2]
Ameloblastoma may occur centrally within the bone or peripherally, without an intraosseous
component in the soft tissues overlying the alveolar ridge. Intraosseous lesions are
of two types solid/conventional/multicystic and unicystic.[3] Unicystic ameloblastoma (UA), a variant of ameloblastoma first described by Robinson
and Martinez[4] in 1977, refers to those cystic lesions that show clinical and radiologic characteristics
of an odontogenic cyst but in histologic examination show a typical ameloblastomatous
epithelium lining part of the cyst cavity with or without luminal and/or mural tumor
proliferation. Before the report by Robinson and Martinez, this variant had been referred
to as a mural or intraluminal ameloblastoma. Recognition of this growth pattern is
very important because of its unicystic radiographic appearance, histologic findings,
association with an unerupted tooth, occurrence in the mandible of younger patients,
and a recurrence rate after conservative surgical treatment lower than that of its
conventional counterpart.[5]
We present a case of a unicystic ameloblastoma in a 10-year-old child patient who
reported with a complaint of swelling of her right lower jaw.
Case Report
A 10-year-old female child came with a complaint of swelling on the right lower side
of her jaw for 1 month which was insidious in onset and got gradually progressed to
the present size. It was associated with severe, intermittent, and dragging type of
pain which radiates to the right ear. Pain relieved with medication. It was also associated
with extraoral swelling for 15 days. On extraoral examination, facial asymmetry was
seen in the right lower third of the face. On intraoral examination, a solitary diffuse
swelling was seen in the buccal vestibular region of 85 and 46, extending anteroposteriorly
from middle third of 85 to distal surface of 46. Superiorly the swelling of the lesion
is extending from attached gingiva of 85 and 46 to inferiorly into the buccal vestibule.
Sinus opening with pus discharge was seen on the attached gingiva of 85 (buccal or
lingual). On palpation, swelling was tender, hard in consistency, noncompressible,
and nonreducible. Expansion of buccal cortical plate was felt in relation to 85 and
46.
Based on the history and clinical examination, a provisional diagnosis of ameloblastoma
was made. Under differential diagnosis, ameloblastic fibroma and odontogenic keratocyst
were considered. Intaoral periapical view (IOPA), occlusal view,orthopantomogram (OPG),
and computed tomography (CT) scan were taken. IOPA taken in relation to 85 and 46
[Figure 1] showed diffuse radiolucency distal to 46 with the absence of 47 tooth bud. OPG [Figure 2] view showed a solitary, well-defined radiolucency of size 3 cm × 2 cm extending
anteroposteriorly from mesial root of the tooth number 46 is 1 cm from the posterior
border of the ramus of the mandible, superoinferiorly 1 cm below the sigmoid notch,
to the inferior border of the mandible thinning the inferior cortical margin. Internal
structure was radiolucent with the displaced tooth bud of 47 in the ramus region.
Figure 1: Intraoral periapical radiograph showing diffuse radiolucency distal to 46
with the absence of 47 tooth bud
Figure 2: Preoperative orthopantomogram showing solitary, well‑defined radiolucency
of size 3 cm × 2 cm surrounding the crown of 47 tooth bud which got displaced into
the ramus region with thinning of the inferior border of the mandible
Panoramic CT section [Figure 3] and sagittal CT section [Figure 4] showed hypodense area of size 2.5 cm × 3 cm surrounding the developing tooth bud
of 47. Axial CT section [Figure 5]a showed tooth within the hypodense area, and axial CT section [Figure 5]b showed buccal cortical plate expansion with breakdown of lingual cortical plate.
Figure 3: Panoramic computed tomography section showing complete extension of the
lesion
Figure 4: Sagittal computed tomography section showing hypodense area surrounding
the developing tooth bud of 47
Figure 5: (a) Axial computed tomography section showing tooth within the hypodense
area (b) Axial computed tomography section showing buccal cortical plate expansion
with breakdown of lingual cortical plate
An incisional biopsy was done and it showed epithelial lining with ameloblast-like
cells and adjacent connective tissue stroma. There was no luminal proliferation of
epithelium, suggestive of intraluminal ameloblastoma [Figure 6]. Following the diagnosis, the parents were informed about the condition and proposed
treatment. Surgical enucleation along with chemical cauterization with Carnoy's solution
[Figure 7] was done under general anesthesia along with extraction of 47 [Figure 8] considering age of the patient. The patient is under follow-up, with no functional
or esthetic complaints. Six months posttreatment, OPG shows signs of new bone formation
[Figure 9].
Figure 6: Low-power histopathological picture of unicystic ameloblastoma showing intraluminal
proliferation
Figure 7: Surgical site of enucleation
Figure 8: Surgical specimen with extracted 47
Figure 9: Postoperative orthopantomogram showing signs of new bone formation
Discussion
UA accounts for 6%–15% of all intraosseous ameloblastomas.[1] It is less aggressive and usually occurs in an earlier age group than the solid
or multicystic with about 50% of the cases occurring in the second decade of life.
As in the present case, >90% of UA are seen affecting the mandibular region,[6] which was also seen in present case. In most cases, UA are associated with impacted
tooth, mandibular third molar being the most common.[7]
The term unicystic is derived from the macroscopic and microscopic appearance, the
lesion being essentially a well-defined, often large monocystic cavity with a lining,
focally but rarely entirely composed of odontogenic (ameloblastomatous) epithelium.[8]
The pathogenesis of cystic ameloblastomas remains obscure. Some investigators believe
that UA arises from preexisting odontogenic cysts, in particular a dentigerous cyst,
while others maintain that it arises de novo. The reason why some ameloblastomas become
completely cystic may be related to epithelial dysadhesion (e.g., defective desmosomes)
or, more likely, to the intrinsic production of proteinases enzymes that normally
degrade the central zone of the enamel organ after tooth development.[9] (e.g., metalloproteinases and serine proteinases).[9]
Radiographically, the unilocular: multilocular ratio is 13:3 when the lesion is associated
with an impacted tooth. For the “nondentigerous” variant, this ratio changes to 8:7.
Further, the “dentigerous” type occurs on average 8 years earlier than the “nondentigerous”
variant. Finally, the mean age for unilocular, impaction-associated UAs is 22 years,
whereas the mean age for the multilocular lesion unrelated to an impacted tooth is
33 years.[7]
Ackermann et al.[10] classified unicystic ameloblastoma into three types with prognostic and therapeutic
implications such as:
-
Group I: Luminal UA (tumor confined to the luminal surface of the cyst)
-
Group II: Intraluminal/plexiform UA (nodular proliferation into the lumen without
infiltration of tumor cells into the connective tissue wall)
-
Group III: Mural (invasive islands of ameloblastomatous epithelium in the connective
tissue wall not involving the entire epithelium).
The microscopic pattern that exhibits mural invasion in UA suggests a more aggressive
potential.[11]
Another histologic subgrouping by Philipsen and Reichart[12] has also been described as follows:
-
Subgroup 1: Luminal
-
Subgroup 1.2: Luminal and intraluminal
-
Subgroup 1.2.3: Luminal, intraluminal, and intramural
-
Subgroup 1.3: Luminal and intramural.
The unicystic ameloblastomas diagnosed as subgroups 1 and 1.2 can be treated conservatively
(enucleation), whereas subgroups 1.2.3 and 1.3 showing intramural growths require
radical resection, as for a solid or multicystic ameloblastoma. Following enucleation,
vigorous curettage of the bone should be avoided as it may implant foci of ameloblastoma
deeper into bone. Chemical cauterization with Carnoy's solution[13] is also advocated for subgroups 1 and 1.2. Subgroups 1.2.3 and 1.3 have a high risk
for recurrence, requiring more aggressive surgical procedures.[14]
Recurrence rates for unicystic ameloblastoma after conservative surgical treatment
(curettage or enucleation) are generally reported to be <25%. For intraluminal and
plexiform type of unicystic ameloblastoma, recurrence rate was found to be as low
as 10.7%.[15] Recurrence rates for solid multicystic ameloblastoma was found to be about 50%–90%.
The present analysis included only publications in English. All well-documented publications
during the last 20 years were collected, and several clinicopathological features
of each case were studied. The following data were recorded: age (≤10 years), sex,
location, clinical features/symptoms, histological type, radiographic appearance,
and treatment. Only reports of unicystic ameloblastoma in children <10 years confirmed
by histological analysis with all the data required for tabulation were included and
the articles not having enough information were excluded [Table 1].
Table 1
English literature review till date
|
Year
|
Author
|
Age
|
Sex
|
Location
|
Clinical features
|
Histological features
|
Radiological features
|
Treatment
|
|
INA – Information not available; UL – Unilocular ameloblastoma
|
|
1998
|
Li etal.[16]
|
10
|
Female
|
Mandible
|
Mild fullness over the cheek
|
Unicystic ameloblastoma
|
UL
|
Enucleation
|
|
2000
|
Li etal.[17]
|
5
|
Male
|
Maxilla (premolar to second molar)
|
Cystic lesion
|
Mural type
|
INA
|
Enucleation
|
|
2003
|
Al-Khateeb and Ababneh[18]
|
9
|
Female
|
Mandible
|
Painless swelling
|
Unicystic ameloblastoma
|
UL
|
Enucleation plus peripheral ostectomy
|
|
2007
|
Huang et al.[19]
|
9
|
Male
|
Body-angle of INA the mandible
|
INA
|
UL
|
Enucleation and peripheral ostectomy
|
|
2008
|
Qureshi et al.[20]
|
10
|
Female
|
Mandible
|
Mild fullness over the cheek
|
Unicystic ameloblastoma
|
UL
|
Enucleation, curettage
|
|
2008
|
Gulten et al.[21]
|
8
|
Male
|
Right mandible
|
Painless hard swelling
|
Unicystic ameloblastoma
|
UL
|
Enucleation and extraction of related teeth
|
|
2011
|
Chacko and Kuriakose[22]
|
9
|
Male
|
Mandible
|
Pain and swelling in relation to the right side of the lower jaw
|
Plexiform unicystic ameloblastoma
|
UL
|
Enucleation, curettage
|
|
2011
|
Kalaskar et al.[23]
|
9
|
Male
|
Right maxilla
|
Painless swelling
|
Unicystic ameloblastoma with intraluminal proliferations
|
UL
|
Enucleation + Carnoy’s solution and extraction of related teeth
|
|
2011
|
Ponniah[24]
|
8
|
Female
|
Left ramus of the mandible
|
Painless swelling on the left side of the mandible
|
Unicystic ameloblastoma
|
UL
|
Enucleation then segmental resection
|
|
2011
|
Sudhakara Reddy et al.[25]
|
6
|
Female
|
Anterior mandible
|
Slow growing painless swelling
|
Unicystic ameloblastoma
|
UL
|
Enucleation and extraction of related teeth followed by application of Carnoy’s solution
|
|
2012
|
Scariot et al.[26]
|
9
|
Female
|
Right mandibular body
|
Painless swelling
|
Plexiform unicystic ameloblastoma
|
UL
|
Curettage with extraction of two adjacent teeth
|
|
2013
|
Bhutia et al.[27]
|
5
|
Male
|
Right mandible
|
painless hard swelling
|
Type 1 unicystic ameloblastoma
|
UL
|
Enucleation of the cyst with extraction of the involved teeth followed by application
of Carnoy’s solution
|
|
2013
|
Arora et al.[28]
|
3
|
Female
|
Left maxilla
|
Bony hard swelling
|
Unicystic ameloblastoma (Type 1.2)
|
UL
|
Enucleation of the cyst with extraction of the involved teeth
|
|
2014
|
Present case
|
10
|
Female
|
Right mandible
|
Swelling with mild pain
|
Unicystic ameloblastoma
|
UL
|
Enucleation with chemical cauterization
|
Conclusion
Ameloblastomas in children differ from adults with a higher percentage of unicystic
tumors. Unicystic ameloblastoma is a tumor with a strong propensity for recurrence,
especially when the ameloblastic focus penetrates the adjacent tissue from the wall
of the cyst. Although enucleation has been claimed to give acceptable recurrence rates
in unicystic ameloblastoma, there are no large series with long follow-up in children.
The histologic pattern that exhibits mural invasion in unicystic ameloblastoma suggests
that more aggressive surgery is necessary. The present case was treated with Carnoy's
solution along with the enucleation, which suggests a possible benefit against recurrence.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient(s) has/have given his/her/their consent for his/her/their
images and other clinical information to be reported in the journal. The patients
understand that their names and initials will not be published and due efforts will
be made to conceal their identity, but anonymity cannot be guaranteed.
