- Oral Surgery, Oral Medicine, Oral Pathology, Oral

Ameloblastic carcinoma: a case report with radiological features
of computed tomography and magnetic resonance imaging
and positron emission tomography
Hidenobu Matsuzaki, DDS,a Naoki Katase, DDS, PhD,b Marina Hara, DDS,c
Jun-Ichi Asaumi, DDS, DMSci,d Yoshinobu Yanagi, DDS,e Teruhisa Unetsubo, DDS, PhD,c
Miki Hisatomi, DDS, PhD,a Hironobu Konouchi, DDS, PhD,e and
Hitoshi Nagatsuka, DDS, PhD,f Okayama, Japan
GRADUATE SCHOOL OF MEDICINE, DENTISTRY, AND PHARMACEUTICAL SCIENCES, OKAYAMA
UNIVERSITY
Ameloblastic carcinoma is a rare malignant odontogenic carcinoma that has metastatic potential, and
because of its rare incidence, there are few reports focusing on its radiologic imaging. If it shows aggressive
appearances, it can be diagnosed as malignant tumor. But in case of negative appearance, it is difficult to distinguish
ameloblastic carcinoma from ameloblastoma. We report a case of ameloblastic carcinoma of the maxilla in a 76-yearold female patient with radiologic images and pathologic features. (Oral Surg Oral Med Oral Pathol Oral Radiol
Endod 2011;112:e40-e47)
Ameloblastic carcinoma, a rare odontogenic carcinoma, is divided into primary type; secondary type,
intraosseous; and secondary type, peripheral in the
World Health Organization (WHO) classification in
2005.1-5 Ameloblastic carcinoma was classified as malignant ameloblastoma in odontogenic carcinomas in
the WHO classification in 1972.6 Thereafter, Elzay7
and Slootweg and Müller8 distinguished ameloblastic
carcinoma from malignant ameloblastoma.
Because ameloblastic carcinoma is a rare occurrence,1-4 many examples are case reports.9-12,14-35
However, some authors have reported literature reviews.9-17,30 According to them, ameloblastic carcinoma has different clinical features in the maxilla and
in the mandible and has a lower incidence in the maxilla than in the mandible.9-11 The radiologic features of
ameloblastic carcinoma are variously reported, and
there are some differential diagnoses, such as cysts,
benign tumors, other malignant tumors, and metastatic
a
Assistant Professor, Department of Oral Diagnosis and Dentomaxillofacial Radiology.
b
Assistant Professor, Department of Oral Pathology and Medicine.
c
Research Fellow, Department of Oral and Maxillofacial Radiology.
d
Professor, Department of Oral and Maxillofacial Radiology.
e
Senior Assistant Professor, Department of Oral Diagnosis and Dentomaxillofacial Radiology.
f
Professor, Department of Oral Pathology and Medicine, Okayama
University.
Received for publication Nov 29, 2010; returned for revision Jan 14,
2011; accepted for publication Jan 18, 2011.
1079-2104/$ - see front matter
© 2011 Mosby, Inc. All rights reserved.
doi:10.1016/j.tripleo.2011.01.023
e40
tumors.9-24,26,28,30-35 Ameloblastic carcinoma tends to
be aggressive and may involve lymph nodes and distant
metastasis.9-20,22,24-28,30-35 Therefore, diagnostic imaging before treatment is very important, but previous
reports are mostly related to clinical courses and pathologic features.9-18,20,30 In particular, there are no reports about 18F-fluorodeoxyglucose–positron emission tomography (FDG-PET) of the primary site, and
only a few images with magnetic resonance imaging
(MRI) and computerized tomography (CT) have
been presented.9-12,14-17,19,21,22,24,26-28,35
In the present report, we show various imaging characteristics of FDG-PET, MRI, including dynamic
study, CT, and conventional radiographs in a case of
ameloblastic carcinoma of the maxilla.
CASE REPORT
A 73-year-old woman referred to a general dental practitioner in 2007 complaining of a painless swelling of right
cheek. Her primary doctor diagnosed a residual cyst of the
maxillary premolar region on the basis of a panoramic radiograph and then followed her. In July 2009, she referred to
Okayama University Hospital because she felt a sense of
discomfort in the right cheek. Her medical history revealed
hypertension, arrhythmia, and cataract. Intraoral examination
revealed a painless, bone-like swelling in the right anterior
maxilla (Fig. 1).
Conventional radiographs showed a unilocular cystic lesion with well defined margins which elevated the floor of the
right anterior maxillary sinus, and a tooth-like radiopaque
body in the alveolar process of the right premolar region (Fig.
2). Contrast-enhanced CT with iohexol was performed to
differentiate between cystic lesions as a residual cyst and
benign tumors as an ameloblastoma. Axial CT (bone window)
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Fig. 1. Intraoral photograph, showing gingival swelling without ulceration in the right anterior maxilla.
image revealed a globular-shaped lesion arising from the
inside of maxillary bone with a slight expansion and anterior
bone resorption of the anterior maxillary sinus (Fig. 3, A).
Contrast-enhanced axial CT image showed a heterogeneous
enhancement of the lesion (Fig. 3, B). On reconstructed
coronal CT image, the mass showed the diffuse bone partly
resorption of alveolar bone and elevated anterior maxillary
sinus floor with destruction of a part of the floor and all of the
nasal side wall (Fig. 3, C). These findings of marginal bone
destruction of the lesion in some parts had the possibility of
malignancy, but we assigned the diagnosis of a benign tumor,
such as ameloblastoma, because the margin of the lesion was
almost well defined. Based on clinical diagnosis of benign
tumor, the incisional biopsy was performed a few days later
and showed that the lesion was suspected ameloblastic carcinoma. Contrast-enhanced MRI with gadodiamide including
dynamic study was performed 12 days later to evaluate soft
tissue invasion at the maxillary sinus and nasal cavity. Furthermore, we performed FDG-PET/CT to investigate the
presence of regional lymph nodes and distant metastasis 14
days after the biopsy.
The MR images showed the mass consisting of a solid
component, which had a predilection for isointensity on T1weighted image (T1WI), hyperintensity on short TI inversion
recovery (STIR) image, and enhancement on contrast-enhanced T1WI, and liquid components, which had a predilection for homogeneous isointensity on T1WI, homogeneous
hyperintensity on STIR, and no enhancement on contrastenhanced T1WI. These findings were similar to ameloblastoma (Fig. 4). Contrast index (CI) curve was created using
dynamic images to observe the flow pattern of contrast medium into the tumor mass. The region of interest (ROI) was
essentially drawn to include the maximal region of solid
portion excluded the cystic portion by free hand drawing
using cursor on monitor. The mean signal intensity (SI) of the
ROI of each lesion was calculated on a workstation (Synapse
Vincent; Fujifilm Medical Co.). The CI was calculated using
the following formula: CI ⫽ (signal intensity (postcontrast) ⫺
signal intensity (precontrast))/signal intensity (precontrast).
Fig. 2. A, Panoramic radiograph shows the cystic radiolucent
lesion in the right maxilla elevating the floor of the right
anterior maxillary sinus. B, Periapical radiograph shows a
tooth-like radiopaque body and diffuse resorption of alveolar
bone in the upper right canine region. C, Water x-ray shows
delineation of nasal sidewall of the right anterior maxillary
sinus.
Then the CI was plotted on a time course to obtain the CI
curve. The CI curve of our case showed gradual increase,
reached a plateau at 90-120 seconds, and nearly sustained the
plateau to 800 seconds (Fig. 5). This appearance also was
similar to ameloblastomas.
On FDG-PET imaging, elevated FDG uptake was found in
the right maxilla (maximum standardized uptake value (SUVmax) 28.3; Fig. 6, A and B). No abnormal high uptake
suggesting the distant metastasis was observed on FDG-PET
images (Fig. 6, C). On the basis of these imaging findings,
the patients were diagnosed with ameloblastic carcinoma
(stage IV, T4N0M0) and underwent tumor resection and
split-thickness skin grafting. After the surgery, the diagnosis
was confirmed histopathologically.
Histologic findings revealed that the tumor mass dominated
in the maxillary bone with giant cyst formation (Fig. 7, A).
The tumor exhibited massive bony destruction and progressed
into the maxillary sinus, invading into gingival connective
tissue and subcutaneous tissue of the cheek region (Fig. 7, B).
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Fig. 3. Computerized tomographic images. A, Axial (bone-window) image shows a large mass in the right anterior maxillary sinus
with destruction of its anterior wall and alveolar bone. B, Contrast-enhanced axial image shows heterogeneous enhancement
within the tumor. C, Reconstructed coronal image with bone condition show the tumor destruction of the elevated right anterior
maxillary sinus floor and nasal sidewall of the right maxillary sinus.
Tumor cells with hyperchoromatism and nuclear polymorphism formed anastamosing strands with edematous
stroma, exhibiting plexiform pattern in some areas (Fig. 7,
C). In another area, the tumor cells presented follicular
growth pattern with desmoplastic stroma, which consisted
of proliferation of hyalinized collagen fibers. The follicular
nests consisted of palisaded columnar cells located in the
outer layer and polygonal or loosely arranged stellate reticulum–like cells located in the inner layer. In the tumor
nests, focal keratinization and/or comedolike necrosis was
observed (Fig. 7, D). Histopathology of the tumor was
similar to the plexiform-type or follicular-type ameloblastoma but accompanied by strong cellular atypia, necrosis,
apoptosis, and mitoses, indicating its malignant features.
Moreover, the tumor lacked the finding of ordinary ameloblastoma. Immunohistochemical stains demonstrated high
positive ratios of p53 and Ki-67 in the tumor cells (Fig. 8).
The lesion was finally diagnosed as ameloblastic carcinoma “primary type” based on the histopathologic and
immunohistochemical findings.
In the follow-up a year after surgery, the patient was free of
recurrence and metastasis.
DISCUSSION
Ameloblastic carcinoma is a rare disease and its
incidence has been reported as 1%-3%.1-4 Ameloblastic
carcinoma has a high incidence in men twice than that
in women; maxilla and mandible location differ in
average age, the 5th decade for the maxilla, which is
⬃10 years older than for the mandible.9-11 The mean
age for ameloblastic carcinoma tends to be higher than
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Fig. 4. Magnetic resonance images in the coronal plane. A, T1-weighted image shows hypo- to isointensity with heterogeneous
pattern. B, Short TI inversion recovery (STIR) image shows heterogeneous hyperintensity with a marked high signal spot. C, On
contrast-enhanced T1-weighted image, the tumor shows well enhancement heterogeneously outside the region which shows
marked hyperintensity on STIR image.
Fig. 5. Contrast index curve of ameloblastic carcinoma shows the pattern that increases relatively, reaches a plateau at 90-120
seconds, and then nearly sustains the plateau to 800 seconds.
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Fig. 6. Axial and coronal 18F-fluorodeoxyglucose–positron emission tomography (FDG-PET)/CT images show the FDG
accumulations of primary tumor in the right maxilla (SUVmax 28.3) A, B, There are no abnormal FDG accumulations suggesting
the metastasis on the FDG-PET image (C).
for ameloblastoma, which affects the genders and jaws
almost the same.36-39
The clinical symptoms of ameloblastic carcinoma are variable, such as gingival swelling with or without ulceration,
rapid growth of mass, perforation of the cortex, pain, and
paresthesia.9-16,30 These symptoms of ameloblastic carcinomas are more aggressive than ameloblastomas.9-11,36-40
Radiographic features of ameloblastic carcinomas were
similar to those of ameloblastomas, and some authors
have reported the presence of the some focal radiopaque
body of dystrophic calcifications.11,14,15,18,19 The radiographic appearance of our case was almost the same as
benign tumors and cysts and had no dystrophic calcification in radiographic and histologic features.
We wrongly diagnosed our case as benign tumor, because the occurrence of ameloblastic carcinoma is rare, it
had a normal-appearing mucosal surface without ulceration, and the margin of the lesion was almost well de-
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Fig. 7. A, Macrographic view of hematoxylin-eosin staining shows that the tumor cells formed an intrabony lesion with giant cyst
formation. B, The tumor showed osteolytic growth. The anterior maxillary sinus wall was destroyed and extravasation into
submucosal tissue was observed. C, Tumor cells formed plexiform growth with loose edematous stroma and D, follicular tumor
nest with cystic degeneration and necrosis accompanied by dense collagenous stroma.
fined although partly destructed on CT images. However,
retrospectively, we recognized the bone resorption of alveolar bone and walls of anterior maxillary sinus due to
bone invasion of the tumor as a characteristic finding
suggestive of malignancy. These findings are not commonly observed in benign tumors and cysts. And such
small changes of bone were more clearly seen in the CT
images compared with conventional radiographs. On the
basis of contrast-enhanced CT images, the lesion could be
diagnosed with tumorous lesions because the inner part of
the mass was enhanced.
MRI could more clearly show internal state of the
lesion, as mentioned by many authors, including us.41-43
In the present case, the lesion showed isointensity and
slight hyperintensity on T1WI, and slight hypointensity,
hyperintensity, and marked hyperintensity on STIR image. Contrast-enhanced T1WI showed inhomogeneous
enhancement with nonenhancement area of liquid component which was a markedly hyperintense area on STIR
image. These patterns of signal intensities were not specific to ameloblastic carcinoma, although they are consistent with the gross features of the resected tumor and the
MRI findings of ameloblastoma.41-43 We have previously
reported dynamic contrast-enhanced MRI of ameloblastomas. We reported that the CI curves of ameloblastomas
show 2 patterns: one increases, reaches a plateau at 100300 seconds, then sustains the plateau or decreases gradually to 600-900 seconds, and the other increases relatively rapidly, reaches a plateau at 90-120 seconds, then
decreases relatively rapidly to 300 seconds and decreases
gradually thereafter.43 This case of ameloblastic carcinoma was consistent with the latter pattern of CI curve, so
it was difficult to differentiate ameloblastic carcinoma
from ameloblastoma.
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Matsuzaki et al.
lymph node metastasis, it is useful to use PET as the initial
staging method before surgery.
Histologic findings revealed that the tumor exhibited an
osteolytic solid mass with multiple cyst formation. The
tumor cells demonstrated plexiform growth and/or stellate
reticulum–like follicular growth pattern, resembling
ameloblastoma. However, it lacked benign ameloblastoma features, and the tumor cells showed strong cellular
atypia, hyperchoromatism, necrosis, and apoptosis. Moreover, immunohistochemistry revealed high positive ratios
for p53 and Ki-67. Taking these together, we diagnosed
the tumor as ameloblastic carcinoma (primary type), according to the WHO classification revised in 2005.
Ameloblastic carcinoma is a very rare intrabony neoplasm and includes metastasizing ameloblastoma and
ameloblastic carcinoma (primary/secondary).5 Differential diagnosis of ameloblastoma and ameloblastic carcinoma is sometimes controversial, because ameloblastoma
will show osteolytic grows although it is benign. Therefore, the findings of cellular atypia or necrosis in the tumor
nest and immunohistochemical analysis for p53 and Ki-67
might be the key to differentiate the two.
Fig. 8. A, Immunohistochemical analysis revealed that the
tumor cells showed diffuse positive reaction for p53. B,
Ki-67–positive cells were observed at high rates, demonstrating the malignant feature of the tumor.
CONCLUSIONS
We have reported a case of amelobastic carcinoma of
the maxilla in a 73-year-old female patient. In our case, it
was difficult to distinguish between tumorous lesion and
cystic lesion by conventional radiographs. CT and MRI
findings suggested it to be tumor but were nonspecific to
ameloblastic carcinoma. FDG-PET/CT was useful for ascertaining the presence of regional lymph node and distant
metastasis. In reviewing our case, CT was useful for
distinguishing ameloblastic carcinoma from ameloblastoma, because it could observe bone resorption clearly.
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as far as we ranged extensively over the literature, there was
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Moreover, the article described only the skull and lung metastasis and not the primary site. They reported that the FDG
accumulations were observed in the skull (SUVmax 6.0) and
lung (SUVmax 2.0) metastasis. In our case, we observed the
strong FDG uptake (SUVmax 28.3) in the primary tumor,
although there were no abnormal FDG accumulations suggesting the metastasis. Because the ameloblastic carcinoma
has a potential of distant metastasis with or without cervical
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Reprint requests:
Junichi Asaumi, DMSci
Field of Tumor Biology
Department of Oral and Maxillofacial Radiology
Graduate School of Medicine, Dentistry and Pharmaceutical Sciences
Okayama University
5-1, Shikata-cho, 2-Chome, Kita-ku
Okayama 700-8525
Japan
[email protected]