Open Journal of Stomatology, 2013, 3, 347-353 OJST Published Online October 2013 (
Hybrid ameloblastoma in a nigerian: Report of a case and
review of literature
O. A. Effiom1*, O. James2, O. T. Akeju3, A. S. Salami3, O. Odukoya1
1Department of Oral Pathology and Oral Biology, College of Medicine, University of Lagos, Lagos University Teaching Hospital,
Lagos, Nigeria
2Department of Oral and Maxillofacial Surgery, College of Medicine, University of Lagos, Lagos, Nigeria
3Department of Oral Pathology and Oral Biology, Lagos University Teaching Hospital, Lagos, Nigeria
Email: *
Received 8 July 2013; revised 8 August 2013; accepted 8 September 2013
Copyright © 2013 O. A. Effiom et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: Hybrid Ameloblastoma is a rare type of
ameloblastoma that is presently receiving attention in
some quarters. Altogether, less than 30 cases have
been reported in the scientific literature, thus calling
for the need to report more cases in order to add to
the body of kn owledge on this lesion. This case report
is aimed to add to the number of cases that are build-
ing up in the scientific literature. Materials and
Methods: A 50-year-old female presented with a
3-year history of an anterior mandibular swelling
extending from the body of the mandible on the right
to the body of the mandible on the left. Orthopanto-
mograph of the lesion revealed a mixed radiolucent
and radiopaque lesion that extended from the distal
region of the right mandibular second premolar to
distal region of the left mandibular second molar.
Segmental mandibulectomy with immediate replace-
ment with reconstruction was undertaken. Results:
Specimen which was subjected to histopathologic
examination reported a diagnosis of Keratinizing Fol-
licular Ameloblastoma and Desmoplastic Ameloblas-
toma with Osteoplasia, consistent with a diagnosis of
Hybrid Ameloblastoma. There has been no sign of
recurrence 7 months after a regular follow-up and the
patient is planned for a long term follow-up. Conclu-
sion: Besides histological details that combine both
conventional ameloblastoma and desmoplastic amelo-
blastoma, the present case of hybrid ameloblastoma
bears similar clinical features as well as treatment
modalities to that of conventional solid multicystic
Keywords: Ameloblastoma; Hybrid; Nigerian
Ameloblastoma is a benign odontogenic tumour of epi-
thelial origin [1,2]. It is found exclusively within the
maxillofacial skeleton (intraosseous or centrally located)
but has been reported to be located in the soft tissue
(gingiva) overlying tooth bearing areas or alveolar mu-
cosa in edentulous regions (extraosseous or peripherally
located) [2]. The WHO in 2005 [2], categorized the con-
ventional ameloblastoma into 4 clinical types namely:
solid multicystic, unicystic, peripheral and desmoplastic
(DA) clinical types. Ameloblastoma is the most common
odontogenic tumour [3], but its precise etiology till date
remains unknown although various etiologies have been
postulated in the scientific literature [4,5]. It is the most
commonly reported tumour in underdeveloped countries
[6] with its highest prevalence recorded in Asian and
African countries [7]. It has been reported to account for
73.0% of odontogenic tumours and 24.0% of tumours
and tumour-like lesions of the jaws [8] and has been ob-
served to occur in both sexes with an equal sex distribu-
tion [9] although a slight male predominance was been
reported [10]. Ameloblastoma affects all age groups with
an average age of 31.67 years but has a site predilection
for the posterior mandible [11]. It usually presents clini-
cally as an asymptomatic jaw swelling.
The main histologic types of the conventional
ameloblastoma include the follicular and plexiform types
although types that cannot be qualified as such are cate-
gorized as mixed types [12]. DA is an unusual variant of
the conventional amelob lastoma. It presents with specific
radio histologic features and anatomic distribution that
make it different from other conventional types [13].
Histologically it is composed of irregular bizarre shaped
proliferating islands an d cords of odontog enic epitheliu m
of different sizes that are embedded in a highly col-
*Corresponding a uthor.
O. A. Effiom et al. / Open Journal of Stomatology 3 (2013) 347-353
laginized connective tissue stroma. Waldron and El-
Mofty [14] discovered a rare variant of ameloblastoma
composed histologically of areas of the classic follicular
or plexiform ameloblastoma and areas of DA. This was
named hybid ameloblastoma (HA).
Ameloblastoma commonly presents radiologically as a
unilocular or multilocular lesion [15] although DA with
osteoplasia and some cases of HA may present with the
more unusual mixed radiolucent and radiopaque pattern
similar to the radiological presentation of fibro-osseous
lesions [15,16]. This uncommon radiological presenta-
tion of ameloblastoma may in some cases pose a diag-
nostic challenge particularly to inexperienced patholo-
gists and surgeons, and may in such cases result in treat-
ment delay. It is therefore important that the clinical, ra-
diological and histological presentations of ameloblas-
toma is well recognized to prevent histological misdiag-
nosis among its various types and to differentiate amelo-
blastoma from other jaw lesions (e.g. fibro osseous le-
sions) which may have similar clinic-radiologic pres-
entations, thus preventing histological misdiagnosis and
inappropriate patient management. Perusal of the scien-
tific English literature reveals that less than 30 cases of
HA hav e been re ported [17 ]. Presen tly we prese nt a case
of HA, a rare type of ameloblastoma and add this to the
scientific literature. In Nigeria, only 2 cases have been
reported [18]. As far as we know, our case would be the
3rd docum e n t ed Ni g erian HA reported so far.
A 50 year old woman presented in the Oral and Maxillo-
facial clinic of the Lagos University Teaching Hospital,
with a well circumscribed anterior mandibular swelling
of 3 years duration (Figure 1). Clinical examination re-
vealed a tumour mass which measured 15 cm × 13 cm
and extended from the mandibular premolar region on
the right to the mandibular 1st molar region on the left
(Figure 2). The tumour was firm to fluctuant in consis-
tency, caused buccal and lingual expansion of the man-
dible and displaced the anterior mandibular teeth. An
orthopantomograph (OPG) was taken and radiographi-
cally the tumour appeared as a mixed radiolucent and
radiopaque lesion with irregular borders primarily lo-
cated in the anterior mandible. The mandibular cortical
bone expansion and displacement of the lower anterior
teeth which were clinically observed were confirmed by
the radiograph (Figure 3). Clinical impressions of
ameloblastoma and ossifying fibroma were made based
on the history an d clinic radiological presentation s. With
an informed consent, an incisional biopsy was per-
formed and a diagnosis of follicular acanthomatous
ameloblastoma was reported (Figure 4). Based on the
histological diagnosis under general anaesthesia, a sege-
Figure 1. Clinical photograph showing gross anterior man-
dibular swelling.
Figure 2. Resected mandible showing well circumscribed le-
sion with buccal and lingual cortical plate expansion and dis-
placement of anterior teeth.
mental resection was performed followed by an immedi-
ate reconstruction of the defect in January 2013.
The post-surgical specimen was subjected to histo-
logical evaluation and this revealed the presence of
ameloblastoma composed of different histological types.
In an area, connective tissue stroma contained odonto-
genic epithelial cells arranged in follicles of peripheral
columnar cells bordering loose central stellate reticu-
lum-like cells that presented with squamous metaplasia,
keratin pearl formation and cystic degeneration (conven-
tional ameloblastoma area) (Figure 5). In another area,
dense connective tissue stroma containing small islands
of compressed odontogenic epithelium was observed.
The compression of the follicles resulted in various figu-
rative pattern presentation of the odontogenic epithelial
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O. A. Effiom et al. / Open Journal of Stomatology 3 (2013) 347-353
Copyright © 2013 SciRes.
Figure 3. OPG showing marked cortical expansion and thinning of cortical
bone, displacement of anterior mandibular teeth, a well defined irregular mul-
tilocular radiolucency and radiopaque specks within the radiolucent area re-
sulting in a mixed radioluency and radioopacity.
Figure 4. Islands of ameloblastomatous follicles in a connective tissue stroma.
Central stellate reticulum cells showing squamous metaplasia in areas, H & E
cells (Figure 6). Areas of osseous metaplasia (osteopla-
sia) were also observed within the dense connective tis-
sue stroma (desmoplastic ameloblastoma with osteopla-
sia area) (Figure 7). A definitive diagnosis of Keratiniz-
ing Follicular Ameloblastoma and DA with Osteoplasia,
consistent with HA was made.
The patient’s post-operative orthopanthomogram and
clinical follow-up after 7 months disclosed no sign of
recurrence and the patient is planned for a long term fol-
low-up (Figure 8).
DA is an uncommon benign locally infiltrative
clinico-surgical type of ameloblastoma. It has been re-
ported to have incidence rates that range from 4.0% -
13.0% [15,16,19]. Histologically, it consists of irregular
bizarrely shaped proliferating islands and cords of odon-
togenic epithelium of different sizes which are embedded
in a highly collaginized connective tissue stroma (des-
moplasia) [15,16,19]. HA on the other hand is a rare type
of ameloblastoma that combines histologic features of
both DA and conventional ameloblastoma. It has been
reported to account for between 1.1% to 4.3% of
ameloblastoma [13,17,18,20,21] and was initially dis-
covered by Waldron and El-Mofty in 1987 to have a
predilection for the posterior aspect of the mandible [14].
Presently we report one case of HA primarily located in
the anterior mandible but with a posterior extension. This
sole case being the only case documented and reported in
40 years, therefore accounts for 0.003% of the series of
ameloblastoma reported at the Lagos University Teach-
ing Hospital (LUTH). Predominant anterior posterior
mandibular tumour site locations of HA have been ob-
served in an earlier study of HA by Takata et al. [22]
O. A. Effiom et al. / Open Journal of Stomatology 3 (2013) 347-353
Figure 5. Islands of odontogenic epithelial cells with peripheral tall columnar
cells and loose central stellate reticulum-like cells showing areas of squamous
metaplasia and keratin pearl formation, H & E ×40.
Figure 6. Islands of odontogenic neoplastic epithelial cells in various patterns
supported by a dense connective tissue stroma, H & E ×40.
while a sole anterior mandibular predilection was re-
ported in a previous Nigerian study [18].
Reports from the scientific literature show that most
cases of HA present as mixed radiolucent and radiopaque
lesions with irregular borders similar to the common
radiological pattern observed in DA (with osteoplasia) or
fibro osseous lesions although a few cases of HA have
been observed to pr esent radio graphically as multi lo cu-
lar radiolucencies similar to the common radiographic
pattern of conventional ameloblastoma [15-18]. There
has been suggestions that the radiographic presentation
of HA (irregular ill-defined borders and mixed radiolu-
cency and radioopacity) may express an infiltrative na-
ture implying HA to be a more aggressive lesion than
other variants of ameloblastoma [13,22]. Although this
case presented radiographicaly as a mixed radiolucent l
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O. A. Effiom et al. / Open Journal of Stomatology 3 (2013) 347-353 351
Figure 7. Area of osteoplasia within the collagenized fibrous connective tissue stroma
in HA, H & E ×40.
Figure 8. Post-operative radiograph of the patient after 7 months disclosed absence
of lesion.
and radiopaque lesion with irregular well d efined bord ers,
it however still presented with similar clinical as well as
similar treatment modalities to that of the conventional
solid multicystic ameloblastoma. The presence of osse-
ous metaplasia (osteoplasia) observed within the desmo-
plastic areas of the lesion may be the result of the pecu-
liar radiographic presentation of the lesion. It is worth
nothing that HA has been observed to share some clinical
features with typical DA namely; anterior mandibular
site predilection, no definite gender predilection and
mixed radiolucent-radioopaque radiographic presenta-
tion. Table 1 summarizes the clinical findings of 25
cases of HA reported in the scientific literature.
There have been suggestions that the term “hybrid” if
taken literally, might overstate the significance of finding
a DA in combination with islands of solid multicystic
ameloblastoma, since the term “hybrid tumour” denotes
2 or more disparate and well established tumours that ex-
hibit obvious differentiation. A suggestion that ‘hybrid
tumour’ be considered a “collision tumour” was there-
fore proposed. [15,23]. Collision tumours are considered
to be 2 or more tumours that arise from independent to-
pographic sites. It is possible that the conventional and
DA variants of the HA develop simultaneously thereby
favoring the collision concept.
Although the clinicopathological and biological charac-
teristics of HA are yet to be precisely established, it is
generally accepted that HA is a variant of the solid mul-
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O. A. Effiom et al. / Open Journal of Stomatology 3 (2013) 347-353
Table 1. Clinico pathologic features of 25 complied cases of Hybrid Ameloblastoma.
Author & Year Number of cases Age/Sex Location Radiologic Features
25 - 82yrs/2-Male 4-Mandible, Posterior NA
Waldron & El Mofty, 1987 5 3-Female 1-NA NA
58yrs/Male Mandible, Anterior to Posterior Soap Bubble & Multicystic
Higuchi et al.., 1991 2 70yrs/Male Mandible, Posterior Multicystic
Philipsen et al., 1992 1 55yrs/Mal e Mandible, Anterior canine
to molar region Multilocular RL with floccular
radiopacities. Root resorption
Ashman et al., 1993 1 53yrs/Mal e Mandible, Anterior Well circumscribed mixed RL & RO
Takata et al., 1999 1 48yrs/Male Mandible, Lateral Incisor to 1st MolarHoney comb appearance in
anterior region
Unicystic RL in molar region
Wakoh et al., 2002 1 35yrs/Female Mandible, Can ine-premolar regionMixed RL & RO with adjacent cystic
radiolucent area
Hirota et al., 2005 1 17yrs/Female Maxilla, Canine & premolar regionsMixed RL & RO with
well defined borders
Santos et al., 2006 1 36yrs/Male Mandible, Anterior-premolar regionIll defined RL
Desai et al., 2006 1 32yrs/Male Mandible, Posterior Well defined unilocular RL
31yrs/Female Mandible, Anterior-premolar Mixed RL & RO with
poorly defined borders
et al., 2009 2 40yrs/ Male Maxilla, Anterior-molar Mixed RL & RO with
ill defined borders
Yazdi et al., 2009 1 48yrs/Female Mandible, Anterior Mixed RL & RO with
ill defined borders
Gade et al., 2010 1 35yrs/Female Maxilla, Anterior Mixed RL with radioopaque specks
Gupta et al., 2011 1 35yrs/Female Mandible, Anterior Ill defined hazy RL
with flecks of RO
Vardhan et al., 2011 1 29yrs/Female Mandible, Anterior-right body Well defined irregular RL
50yrs/Female Mandible, Anterior Multilocular RL
Lawal et al., 2011 2 29yrs/Male Mandible, Anterior Multilocular RL
Acharya et al., 2011 1 50yrs/Male NA NA
Angadi et al., 2011 1 64yrs/Female Maxilla, Anterior-molar Ill defined hazy RL & RO, root
Present case 1 50yrs/Female Mandible, Anterior-molar Mixed RL & RO
NA—Not Available; M—Male; F— Female, RL—Radiolucency, RO—Radiopacity.
ticystic ameloblastoma. Besides the histological details
that combine both conventional ameloblastoma and DA,
our present case of HA bears similar clinical and radio-
logical features as well as similar treatment modalities to
that of the conven tional solid multicystic ameloblasto ma.
We therefore further add a case of this rare form of
ameloblastoma to scientific literature. The frequency of
occurrence of HA in our series however appears very
low. In the light of our new experience, it would be nec-
essary to revisit our archives with the possibility that we
might be able to bring out more cases of HA.
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