Dr. Ahmed M. Adawy, Professor Emeritus, Dep. Oral & Maxillofacial Surgery. Former Dean, Faculty of Dental Medicine, Al-Azhar University. Ameloblastoma is benign slow-growing but locally invasive neoplasm of odontogenic origin. In 2005, the WHO has classified ameloblastomas into multi cystic, unicystic and peripheral subtypes. The clinical picture, radiographic findings and differential diagnosis are presented. Treatment of ameloblastomas is primarily surgical. There has been some debate regarding the most appropriate method for removing. These range from conservative to radical modes. Some authors advocate conservative approach and thought that ameloblastoma are essentially benign in nature and should be treated as such. However, this conservative approach result in recurrence rates of 55% to 90%of the cases. Currently, the standard of care for ameloblastoma includes en bloc resection with 1-2 combine margin and immediate bone reconstruction. Despite the medical nature of a surgical resection, it may actually involve less morbidity than extensive hard and soft tissue resection with associated extensive morbidity that may be warranted in case of recurrence following inadequate primary treatment.

2. Dr. Ahmed M. Adawy
Professor Emeritus, Dep. Oral & Maxillofacial Surg.
Former Dean, Faculty of Dental Medicine
Al-Azhar University

3. Ameloblastoma is benign, slow-growing but locally
invasive neoplasm of odontogenic origin. Theoretically,
it may arise from the cell rests of the enamel organ,
remnants of dental lamina, epithelial lining of an
odontogenic cyst, or basal epithelial cells of the oral
mucosa (1). The name “Ameloblastoma” is derived from
the old English word ‘‘amel’’ which means enamel, and
the Greek word ‘‘blastos’’ meaning germ. It is the second
most common odontogenic tumor after Odontomes in
prevalence and accounts for approximately 1% of all oral
tumors and 18% of all odontogenic tumors

4. Approximately 80% arise in the mandible, most commonly in
the molar-ramus region, occasionally associated with impacted
third molars and the remainder occur in the maxilla (2). The
peak incidence is in the 3rd-4th decades of life and the male to
female ratio is 1:1

5. Based on clinicoradiographic findings,
ameloblastoma is classified into multicystic
(solid), unicystic and peripheral subtypes.
Multicystic ameloblastoma is the most common
type and represent 86% of cases. Peripheral
tumors occur solely in the soft tissues covering
the tooth-bearing parts of the jaws and have the
histological characteristics of intraosseous
ameloblastoma (3)

6. Unicystic ameloblastoma has been identified as a separate
entity in 1977 (4). Two histologic variants of unicystic
ameloblastoma are described, mural ameloblastomas
and luminal ameloblastomas. In mural ameloblastoma,
the fibrous wall of the cyst is infiltrated with tumor
nodules. In luminal ameloblastoma, the tumor is
confined to the luminal surface of the cyst. The tumor
often occurs as a painless swelling involving the posterior
region of the mandible in younger patients.
Radiographically, the tumor presents primarily as a
unilocular radiolucency. This variant of ameloblastoma
was reported to have less aggressive behavior than the
conventional multicystic ameloblastoma

7. Unicystic ameloblastoma

8. Histopathologically, ameloblastoma has six types
namely; acanthomatous, granular cell,
desmoplastic, basal cell, follicular and plexiform
whereas, the last two types are more common.
Though the treatment options and recurrence rate
are irrespective to its histological variants (5)

9. Most common histological subtypes of ameloblastoma;
follicular and plexiform

10. Two rare forms of malignancy are associated with
ameloblastoma: malignant ameloblastoma and
ameloblastic carcinoma. The cardinal feature of malignant
ameloblastoma is metastatic spread. The histologic
appearance of the primary and metastatic lesions is
indistinguishable from benign ameloblastoma. In contrast,
the primary and metastatic lesions of an ameloblastic
carcinoma show histologically malignant epithelial
features similar to an epidermoid carcinoma (6)

11. The diagnosis of ameloblastoma is suggested by
nonspecific radiographic findings and a thorough
physical examination. Nevertheless, a definitive
diagnosis is only obtained through a
histopathological examinations
Diagnosis

12. Typically ameloblastoma present as painless slow growing
swelling that can progress to great size and cause facial
asymmetry, though it may be discovered during routine
radiographic examinations. Pain with rapid growth may
represent the rare malignant ameloblastoma. Tooth
displacement and root resorption are infrequent and
usually is an indication of the aggressive nature of the
lesion. Paresthesias are uncommon, and can result from
perineural invasion

15. Radiographically, ameloblastoma shows radiolucent lesion that
may have either a unilocular or multilocular appearance.
Unicystic ameloblastoma may expand the cortical plate and
gives rise to a paper-thin appearance osteolytic lesion usually
with scalloped margins, resorption of tooth roots, and impacted
molars. The classic ‘‘soap bubble or honeycomb’’ appearance is
seen with the most common ameloblastoma, the multilocular
type (7). plain X-rays are however, of limited value and lack
sensitivity and specificity for the extent of bone and soft tissue
invasion

17. Computed tomography (CT) is the most useful
diagnostic imaging modality, typically demonstrating
well defined radiolucent uni/multilocular expansible
lesions. CT is also useful for the evaluation of cortical
destruction and soft tissue extension, identifying the
full extent of the tumor to support surgical planning

18. C T, axial and coronal sections

19. 3-D reconstruction demonstrated a great multicystic ameloblastoma

20. Differential Diagnosis
However, even when an ameloblastoma shows the
typical expansive multilocular appearance, the
differential diagnosis can include a variety of
odontogenic and nonodontogenic lesions with similar
radiographic characteristics namely; aneurysmal bone
cyst, odontogenic keratocysistc tumor, ameloblastic
fibroma, odontogenic myxoma, giant cell lesions and
brown tumor of hyperparathyroidism

21. When the lesion presents with a cystic, unilocular and
well-defined aspect, the differential diagnosis is
typically of odontogenic keratocysistc, dentigerous
cyst, residual and radicular cysts or even a traumatic
bone cyst. Additionally, peripheral ameloblastomas
may resemble lesions such as fistulas, pyogenic
granulomas, peripheral giant cell lesions and
peripheral odontogenic fibromas (8)

23. Treatment of ameloblastomas is primarily surgical. There
has been some debate regarding the most appropriate
method for surgical removal of ameloblastomas. These
range from conservative to radical modes of treatment.
The conservative modalities include enucleation and
curettage; while the radical modalities are marginal,
segmental and composite resections. Those advocate
conservative approach believe that ameloblastomas
though, locally invasive, are essentially benign in nature,
therefore, they should be treated as such (9)

24. Conservative approach in the form of enucleation and
curettage is still commonly practiced, despite reported
recurrence rates of 55% to 90% for solid multicystic
treated conservatively(10). To limit recurrence rates of
unicystic ameloblastomas, oral surgeons have extended
this procedure to include intra-operative adjuvant
treatment of the bony margins with cryotherapy(11), tissue
fixatives such as Carnoy’s solution(12), drilling and
cautery. The outcomes of the these procedures
demonstrate decreased recurrence rates, but still higher
recurrences compared with the more extensive radical
procedures

25. The ‘‘radical’’ surgical option is the current standard of
care for ameloblastoma and includes en bloc resection
with 1–2 cm bone margins (13) and immediate bone
reconstruction. The bony margin is defined as the distance
away from the radiographic margin predicted to be disease
free and safe to perform osteotomies. It has been
documented that ameloblastoma specimens showed
microscopic tumor extension 2–8 mm beyond the
radiographic boundaries of the tumor (14). Hence, the
recommended bone margins are 1–1.5 cm for unicystic
and 1.5–2 cm for multicystic histological types. The
healthy mucosa overlying cortical perforation is often
removed as a margin

26. Segmental resection of the mandible results in
discontinuity of the jaw, which is stabilized to its
previous position by titanium reconstruction plates to
ensure proper occlusion. A fibular free flap is used to
restore bone continuity and allow for dental restoration.
Reconstructive outcomes show a high rate of success
for both esthetic and functional outcomes (15)

27. Following segmental resection, the defect is bridged by
free fibular graft and reconstruction plate

28. Rehabilitation with dental implants

29. Despite the ‘radical’ nature of a surgical resection, it
may actually involve less morbidity than extensive
hard and soft tissue resection with associated
extensive morbidity that may be warranted in case
of recurrence following inadequate primary
treatment

30. Follow-up of patients with ameloblastoma should
be carried out regularly. As most recurrences
present within the first 5 years, yearly follow-up
during this period is advisable. Thereafter, follow-
up every 2 years seems appropriate but should
extend for at least 25 years, as recurrences may
appear after a long time (16)

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