Desmoplastic Ameloblastoma (a Hybrid Variant) Report of a Case

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Arch Iranian Med 2009; 12 (3): 304 – 308

Case Report

Desmoplastic Ameloblastoma (a Hybrid Variant): Report of
a Case and Review of the Literature
•
Ismail Yazdi DMD*, Maryam Seyedmajidi DMD **, Ramin Foroughi DMD**

Desmoplastic ameloblastoma is an unusual type of ameloblastoma with special histologic and
radiographic features and anatomic distribution which differs from those in the classic type of
ameloblastoma. The purpose of this article is to assist the dental community in better
understanding of this variation of odontogenic tumor. We present a patient with desmoplastic and
conventional variant of ameloblastoma (hybrid lesion) localized in the anterior portion of the
mandible. The tumor was expansile and painless. The radiographic finding showed an ill-defined
mixed (radiopaque/radiolucent) lesion between roots of the lower left canine and the lateral incisor.
Marginal resection was performed. Follow-up examination one year later revealed no recurrence of
the tumor. Desmoplastic variant of ameloblastoma tends to infiltrate between bone trabeculae.
Curettage leaves islands of the tumor within bone, which later manifest as recurrences. Therefore,
for big lesions en bloc excision is the most widely used treatment to avoid recurrence.

Archives of Iranian Medicine, Volume 12, Number 3, 2009: 304 – 308.

Keywords: Ameloblastoma • anterior • desmoplastic • jaw • odontogenic tumor

Introduction neoplasm extends through cancellous bone, but
usually is confined by compact bone such as the

A
meloblastoma is a benign epithelial inferior border and ascending ramus of the
odontogenic tumor that usually exhibits mandible. These sites seem to act as effective
aggressive behavior. It expands barriers that delay spreading of the tumor for some
severely to the cortical bones and may have a high time.2,3 Desmoplastic ameloblastoma (DA) does
recurrence rate. It also may cause mobility and not have these characteristics and is a variant that
displacement of the teeth, as well as root was initially documented in the literature in 1984
resorption.1 Some researchers and clinicians have by Eversole et al.4 DA has a marked predilection to
considered ameloblastoma as a low-grade occur in the anterior regions of the jaws,
malignant tumor.2 Malignant ameloblastomas and particularly the maxilla. Radiographically, this
ameloblastic carcinomas are known variants. This type seldom suggests ameloblastoma and usually
tumor occurs most frequently in the posterior resembles to a fibro-osseous lesion because of its
mandible, and usually appears as a well- mixed radiolucent and radiopaque appearance. The
demarcated unilocular or multilocular radiolucent mixed radiographic appearance is due to osseous
lesion that can be associated with a crown of a metaplasia within the dense fibrous septa that
nonerupted tooth. The margins of this lesion, characterizes the lesion, and it is not because of the
however, often show irregular scalloping. The production of a mineralized product by the
tumor.1,4
Authors’ affiliations: Department of Oral and Maxillofacial Histopathologically, ameloblastoma exhibits
Pathology, *Dental Faculty, Tehran University of Medical
Sciences, Tehran, **Babol University of Medical Sciences, Babol,
proliferating odontogenic epithelium within a
Mazandaran, Iran. background of fibrous stroma. The epithelium is
•Corresponding author and reprints: Maryam Seyedmajidi characterized by prominent palisading of the basal
DMD, Department of Oral and Maxillofacial Pathology, Dental
Faculty, Babol University of Medical Sciences, Babol, cell nuclei (i.e., reverse polarization) and by
Mazandaran, Iran. Tel: +98-111-229-14-08-Ext, 116 vacuolization of the cytoplasm of the basal cells.
Fax: +98-111-229-10-93 Within the epithelial islands, stellate reticulum-like
E-mail: ms_majidi79@yahoo.com
Accepted for publication: 22 May 2008 areas may be noted. Foci of squamous-like

304 Archives of Iranian Medicine, Volume 12, Number 3, May 2009
I. Yazdi, M. Seyedmajidi ,R. Foroughi

changes, granular cells, clear cells, and basaloid 2001, Philipsen et al. reviewed the 100 cases of
cells, as well as follicular, cystic, and plexiform DA reported in the literature from Japanese,
patterns, give clues to the histologic variants of this Western, Chinese, Malaysian, Black, and Indian
lesion. Some of the variations in histologic patterns populations from 1984 through 2001.11 A further
appear not to have significant bearing on 50 cases have been reported since then.8, 12–26 The
prognosis. Desmoplastic variant is an unusual type growing knowledge regarding the clinico-
of ameloblastoma with special histologic and radiographic presentation and pathology of DAs
radiographic features. It is also more complicated has led to its categorization as a distinct variant of
to be treated because of its tendency for ameloblastoma in the World Health Organization
penetrating the surrounding bone. Recurrence of (WHO) classification of odontogenic tumors in
solid type ameloblastoma may take place in the 2003. Other variants are solid multicystic
first two years, but some recur after four to five or ameloblastoma (SMA), unicystic ameloblastoma,
more years following initial surgery; therefore, and peripheral extraosseous ameloblastoma.27
patients need to be followed up longer.5 In this article, we present the clinico-pathologic
In one study, immunolocalization of features of a case of DA in Iran.
transforming growth factor beta (TGF-β), one of
the most potent local factors for modulating Case Report
extracellular matrix formation, was observed in
DA in order to study its participation in the stromal A 48-year-old woman visited an oral and
desmoplasia. Seven cases of DA, including a maxillofacial surgeon for evaluation and treatment
hybrid lesion, were studied together with ten cases of an expansile lesion of the anterior mandible that
of ordinary follicular and plexiform extended from the left canine to the left lateral
ameloblastomas as the control. In contrast to incisor area. The lesion had been present for four
ordinary ameloblastomas, marked immune- months. The patient’s medical history revealed
expression was observed in all DAs but one. In the nothing significant.
hybrid lesion, TGF-β was not expressed in the area The patient reported a history of a slowly
of follicular ameloblastoma but in that of DA. enlarging anterior mandibular mass, without
These results show that TGF-β produced by tumor bleeding, pain, or sensory changes. The clinical
cells of DA plays a role in the desmoplastic matrix examination revealed buccal cortical expansion of
formation.6 the anterior mandible. The intraoral examination
A unique case of DA is reported by Kawai et al. disclosed a large, hard, nontender mass of the
Biopsy specimens from the anterior portion of the anterior mandible, covered by an intact overlying
lesion displayed typical histologic features of the mucosa. No lymphadenopathy or fistulae were
desmoplastic variant of ameloblastoma. However, present. The involved teeth were vital and
those from the posterior portion disclosed a large exhibited no mobility. Periapical radiography
cystic formation. Oxytalan fibers were identified in showed a mixed lesion of the mandible with
the stromal tissue of the tumor, which suggested poorly-defined borders mimicking fibro-osseous
that the tumor arose from the epithelial rests of lesions (Figure 1). The differential diagnosis
Malassez in the periodontal membrane of the included focal cement-osseous dysplasia, cemento-
related tooth.7
Till date, 150 cases of DA have been reported
in Japanese, Chinese, Malaysian, Western, African
,and Indian populations.8 The first detailed report
on the desmoplastic variant of ameloblastoma in
the English literature was given by Eversole et al.
in 1984 who called it an 'ameloblastoma with
pronounced desmoplasia.'4 However, Takigawa et
al.9 and Uji et al.10 were the early ones to draw
attention to this unusual variant, characterized by
extensive stromal desmoplasia with small
compressed nests and strands of odontogenic Figure 1. The radiographic finding: Ill-defined mixed
(radiopaque/radiolucent) lesion between roots of the
epithelium. Radiographically, this variant exhibited lower left canine and the lateral incisor, and
no features of conventional ameloblastoma. In displacement of the teeth.

Archives of Iranian Medicine, Volume 12, Number 3, May 2009 305
Desmoplastic ameloblastoma

ossifying fibroma, and odontogenic tumors.
The oral surgeon administered a local anesthetic
agent and performed an excisional biopsy by
marginal resection. A piece of cream-gray elastic
soft tissue with the size of 0.7×0.5×0.4 cm in
formalin was received. Histologically, irregular
odontogenic islands with a stretched-out 'kite-tail'
appearance were seen in a dense desmoplastic
stroma. Tumor elements were present between
bone trabeculae. The peripheral layer of the
epithelial islands and the inner core were made up
of flattened cells and spindle-shaped, respectively. Figure 3. Irregular odontogenic islands with a
Odontogenic epithelium in the form of follicles, stretched-out kite-tail appearance in a dense
desmoplastic stroma (hematoxylin-eosin stain, ×40).
which is typical for SMA, and irregular stretched-
out epithelial islands were observed in a insidious than mandibular tumors owing to the
desmoplastic background. This was categorized as proximity of vital structures and the maxillary
'hybrid' variant of DA (Figures 2 and 3). Collagen sinus. Also, the very thin cortical bone of the
fibers of the stroma stained by van Gieson were maxilla forms a weak barrier for the spread of
demonstrated desmoplasia (Figure 4). The tumors. Consequently, maxillary ameloblastomas
diagnosis was DA. The patient’s postoperative may be able to spread earlier and more quickly
course was uneventful. Postoperative radiography than mandibular neoplasms.7
and a clinical follow-up examination one year later The radiographic appearance of this neoplasm
disclosed no recurrence or residual tumor. usually indicates a mixed radiolucent/radiopaque
lesion. Approximately half of these lesions have
Discussion diffuse borders in the radiography28 and look
similar to a fibro-osseous lesion or malignant
DA exhibits important differences in anatomic tumor. The lamina dura also is involved.29The
distribution, histologic appearance, and radiographic appearance may indicate that this
radiographic findings compared with other types of tumor is more aggressive than other variants of
ameloblastoma. However, age and sex ameloblastoma.30
distributions do not differ from those seen in Waldron and El Mofty31 described the
patients with other types of ameloblastoma.7 histologic appearance of DA as small ovoid islands
Approximately half of the desmoplastic lesions and narrow cords of odontogenic epithelium
are located in the maxilla, and the vast majority of widely separated by dense, moderately cellular,
them occur in the anterior or premolar portion of fibrous, and connective tissue. Although columnar
the jaws. In contrast unicystic or classic types of cells with reverse polarity within the epithelial
ameloblastoma are usually found in the posterior islands are present, they are not the dominant
area of the mandible. Maxillary lesions are more feature. Spicules of mature lamellar bone
trabeculae have been reported in intimate contact
with the tumor, and invasion has been

Figure 2. Odontogenic epithelium in the form of
follicles typical of solid multicystic ameloblastoma and
the irregular stretched-out epithelial islands and
osseous metaplasia (osteoplasia) in a desmoplastic Figure 4. Collagen fibers stained by van Gieson were
background (hematoxylin-eosin stain, ×40). demonstrated desmoplasia (van Gieson stain, ×100).

306 Archives of Iranian Medicine, Volume 12, Number 3, May 2009
I. Yazdi, M. Seyedmajidi ,R. Foroughi

demonstrated. This histologic finding may indicate The biologic behavior of DA is still not fully
the potential for local invasion, and accounts for understood. This lesion will remain an enigma
the diffuse radiographic imaging. until researchers pursue more definitive tumor
DA may exhibit a more aggressive behavior analysis techniques and aggressive follow-up and
than other types of ameloblastoma. Various facts tracking in many more cases.
about this lesion may suggest aggressiveness:
– A potential to grow to a large size31; References
– The common location in the maxilla that may
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308 Archives of Iranian Medicine, Volume 12, Number 3, May 2009

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