Benign Tumours Involving the Jaws










153
Atlas of Oral and Maxillofacial Radiology, First Edition. Bernard Koong.
© 2017 John Wiley & Sons Ltd. Published 2017 by John Wiley & Sons Ltd.
ODONTOGENIC BENIGN TUMOURS
10.1 Ameloblastoma
(Figures10.1–10.9)
Synonym: adamantinoma.
Benign, slow‐growing but locally aggressive tumour of odon-
togenic epithelium.
Three subtypes: solid/multicystic (by far the most common
subtype), unicystic and desmoplastic.
Malignant forms or transformation are very rare:
malignant ameloblastoma (histologically benign but with
metastases)
ameloblastic carcinoma (ameloblastoma with histologi-
cal malignant features).
Any age group but more common in the third to sixth decades.
Most commonly seen in the posterior mandible. Maxillary
lesions most commonly occur posteriorly.
Usually asymptomatic until it causes painless swelling.
Large lesions may involve adjacent structures, including the
upper airway passages, orbit and skull base. Posterior maxillary
lesions are of particular concern in this regard.
Surgical excision beyond radiologically identified margins.
May involve resections.
High recurrence rate, especially the more solid/multicystic sub-
type. Requires radiological review over an extended period.
Radiological features
Multidetector computed tomography (MDCT) usually dem-
onstrates more features but cone beam computed tomography
(CBCT) may be sufficient. 2D radiography is insufficient.
Magnetic resonance imaging (MRI) may be useful in some
cases. MDCT is best for surgical planning as MRI (with gado-
linium) may overestimate the extent of the lesion.
Most commonly presents as a multilocular lesion (solid/
multicystic) with well‐defined corticated or sclerotic borders.
The internal septa are classically thick and curved. Some
may demonstrate the classic ‘soap bubble’ appearance.
The cystic locules vary in size and one or a few may be sub-
stantially larger than others.
The unicystic ameloblastoma is unilocular (lucent internally)
and often demonstrates extreme expansion for its size. Most
are associated with the unerupted mandibular third molars.
The desmoplastic subtype may demonstrate more internal
septa, which are more irregular and sclerotic in appearance.
Unless small, the jaw cortices are usually expanded and
thinned, with regions of effacements.
When involving a tooth root, there is often substantial root
resorption. Tooth displacement is often seen when the lesion
abuts the crown.
MDCT – soft tissue algorithm: solid/multicystic lesions
demonstrate variably heterogeneous overall soft tissue
density attenuation between the septa. Sometimes, the
hypodense cystic locules are demonstrated within.
Occasionally, one or a few of the locules are particular
large, usually of internal fluid density. Larger lesions tend
to demonstrate heterogeneous contrast enhancement, with
non‐enhancing hypodense foci.
MRI: solid/multicystic lesions components demonstrate
heterogeneous T1 low to intermediate signal and T2 inter-
mediate to bright signal. Larger cystic locules demonstrate
homogeneous T1 low to intermediate signal and T2/short
T1 inversion recovery (STIR) hyperintensity. Solid portions
and septations usually enhance. Larger cystic locules usually
demonstrate rim enhancement.
Differential diagnosis
Key radiological differences
Other lesions which may
appear multilocular
including:
Giant cell granuloma Internal septa are usually much finer
than the ameloblastoma. Also usually
seen in the younger population
(unless brown tumour related to
hyperparathyroidism).
Odontogenic myxoma Presence of one or a few straight septa
is a feature. Typically demonstrates
mild expansion for size.
CHAPTER 10
Benign Tumours Involving theJaws

154 Atlas of Oral and Maxillofacial Radiology
Aneurysmal bone cyst Fine internal septa and typically
extremely expansile.
Ossifying fibroma When this lesion demonstrates
appearance of internal septa, they
tend to be larger and less distinct.
Keratocystic odonto-
genic tumour
Internal septa are uncommon and
mandibular lesions demonstrate
mild expansion for size.
Vascular malformation/
haemangioma
Often demonstrates serpiginous
appearance. Prebiopsy evaluation
withMRI should be considered if this
suspected.
Dentigerous cyst May not be able to radiologically
differentiate from the unicystic
ameloblastoma in a pericoronal
relationship with an unerupted tooth.
(a)
(b) (c)
(d)
Substantial buccal lobulated
expansion with severe thinning and
focal effacements of the cortex
Well-defined multilocular
appearance with sclerotic
borders. Note the coarse
curvilinear internal septa
Slightly heterogeneous
internal appearance largely of
soft tissue density with focal
lower density regions
Root resorption
Figure10.1 Ameloblastoma of the left mandible: axial (a), coronal (b) and corrected sagittal (c) bone and axial soft tissue (d) MDCT images.

Benign Tumours Involving theJaws 155
Well-defined multilocular
appearance with well-defined
corticated borders
Heterogeneous internal
appearance with soft
tissue and fluid density
regions
Expansion
(a)
(b) (c)
(d)
Figure10.2 Ameloblastoma (solid/multicystic) of the left maxilla: axial (a), corrected sagittal (b) and corrected coronal (c) bone and axial soft tissue
(d)MDCT images.
Substantial buccal
expansion for size, with
severe thinning and focal
effacements of the cortex
A particularly large
locule of this lesion
Well-defined
corticated borders
Figure10.3 Ameloblastoma (solid/multicystic) of the right mandible: axial MDCT image.

156 Atlas of Oral and Maxillofacial Radiology
Sclerotic
borders
Root resorptionIncidental bone
islands
Multilocular internal
appearance with multiple
small locules and densely
sclerotic septa
Figure10.4 Ameloblastoma (solid/multicystic) of the left posterior body of the mandible: cropped panoramic radiograph.
Root resorption
Substantial expansion
with severe thinning and
likely effacement of the
cortex
Well-defined corticated
borders
Tooth displacement
Figure10.5 Unicystic ameloblastoma of the left posterior mandible: cropped panoramic radiograph.

The large locule with buccal
expansion and cortical
effacement. The lesion
remains contained (soft tissue
window)
Multilocular (multicystic/solid)
component. Note the expansion
seen in the axial image
One of the locules is substantial-
ly larger than the others
Overall soft tissue density
appearance of the more
multicystic/solid component
Internal fluid attenua-
tion of the large locule
(a)
(b)
(c)
(d)
Figure10.7 Ameloblastoma (solid/multicystic) of the right body of the mandible (also refer to MRI of this case in Figure 10.6): MDCT; corrected sagittal
(a), corrected coronal (b) and axial (c) bone and axial soft tissue (d) images.
Figure10.6 Ameloblastoma (solid/multicystic) of the right body of mandible (also refer to MDCT of this case in Figure 10.7): MRI; axial STIR (a),
corrected sagittal STIR (b), axial T1 postgadolinium fat‐saturated (c) and corrected sagittal T1 (d) images.
Heterogeneous intermediate to
increased signal of the
solid/multicystic component
Homogeneous hyperintense
fluid of the larger cystic locule
Enhancement of the
solid/multicystic
component
Rim enhancement of
the larger cystic
locule
Heterogeneous low to
intermediate signal of the
solid/multicystic component
Homogeneous
intermediate signal of the
enlarged cystic locule
(a)
(b)
(c)
(d)

158 Atlas of Oral and Maxillofacial Radiology
Multiple small foci of multilocular
lesions. The locules are typically small
with particularly sclerotic borders
(a)
(b)
Figure10.9 Recurrent ameloblastoma of a right mandibular fibular graft: axial MDCT images (a,b).
Figure10.8 Unicystic ameloblastoma of the left posterior mandible: coronal (a), axial (b) and corrected sagittal (c) MDCT images.
Root resorption
Inferiorly displaced mandibular
canal with effacement of the
superior border
Substantial expansion with
lobulated appearance. There is
severe thinning and focal
effacements of the cortex
(a)
(b)
(c)

Benign Tumours Involving theJaws 159
10.2 Calcifying epithelial odontogenic
tumour
(Figure10.10)
Synonyms: Pindborg tumour, CEOT.
Rare locally invasive epithelial odontogenic tumour with
amyloid‐like material where there may be calcific foci.
Asymptomatic until expansion is noted.
More commonly seen in the posterior mandible, many associ-
ated with unerupted teeth.
Surgical excision. This lesion is considered less aggressive
than the ameloblastoma but postsurgical radiological review
over an extended period is recommended.
Radiological features
MDCT demonstrates more features than CBCT.
Variable presentation:
may be unilocular or multilocular
may demonstrate substantially variable internal calcifications
borders are also variable, ranging from well‐defined cortex
to poorly defined destructive margins.
May displace teeth.
Differential diagnosis
Key radiological differences
May resemble unilocu-
lar lucent lesions such as
cystic lesions, multi-
locular lesions or lesions
which demonstrate
internal calcifications
The more common location of the
calcifying epithelial odontogenic
tumour (CEOT) in the posterior
mandible, associated with an
unerupted tooth, may be a useful
feature.
Subtle internal opacity, more
apparent in the soft tissue
window
Destructive lesion with
enhancing soft tissue mass
(a) (b)
Figure10.10 Calcifying epithelial odontogenic tumour: axial bone (a) and postcontrast soft tissue (b) MDCT images.

You're Reading a Preview

Become a DentistryKey membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here

Was this article helpful?

153Atlas of Oral and Maxillofacial Radiology, First Edition. Bernard Koong. © 2017 John Wiley & Sons Ltd. Published 2017 by John Wiley & Sons Ltd.ODONTOGENIC BENIGN TUMOURS10.1 Ameloblastoma (Figures10.1–10.9)• Synonym: adamantinoma.• Benign, slow‐growing but locally aggressive tumour of odon-togenic epithelium.• Three subtypes: solid/multicystic (by far the most common subtype), unicystic and desmoplastic. ◦Malignant forms or transformation are very rare: ■ malignant ameloblastoma (histologically benign but with metastases) ■ ameloblastic carcinoma (ameloblastoma with histologi-cal malignant features).• Any age group but more common in the third to sixth decades.• Most commonly seen in the posterior mandible. Maxillary lesions most commonly occur posteriorly.• Usually asymptomatic until it causes painless swelling.• Large lesions may involve adjacent structures, including the upper airway passages, orbit and skull base. Posterior maxillary lesions are of particular concern in this regard.• Surgical excision beyond radiologically identified margins. May involve resections.• High recurrence rate, especially the more solid/multicystic sub-type. Requires radiological review over an extended period.Radiological features• Multidetector computed tomography (MDCT) usually dem-onstrates more features but cone beam computed tomography (CBCT) may be sufficient. 2D radiography is insufficient. Magnetic resonance imaging (MRI) may be useful in some cases. MDCT is best for surgical planning as MRI (with gado-linium) may overestimate the extent of the lesion.• Most commonly presents as a multilocular lesion (solid/ multicystic) with well‐defined corticated or sclerotic borders. ◦The internal septa are classically thick and curved. Some may demonstrate the classic ‘soap bubble’ appearance. ◦The cystic locules vary in size and one or a few may be sub-stantially larger than others.• The unicystic ameloblastoma is unilocular (lucent internally) and often demonstrates extreme expansion for its size. Most are associated with the unerupted mandibular third molars.• The desmoplastic subtype may demonstrate more internal septa, which are more irregular and sclerotic in appearance.• Unless small, the jaw cortices are usually expanded and thinned, with regions of effacements.• When involving a tooth root, there is often substantial root resorption. Tooth displacement is often seen when the lesion abuts the crown.• MDCT – soft tissue algorithm: solid/multicystic lesions demonstrate variably heterogeneous overall soft tissue density attenuation between the septa. Sometimes, the hypodense cystic locules are demonstrated within. Occasionally, one or a few of the locules are particular large, usually of internal fluid density. Larger lesions tend to demonstrate heterogeneous contrast enhancement, with non‐enhancing hypodense foci.• MRI: solid/multicystic lesions components demonstrate heterogeneous T1 low to intermediate signal and T2 inter-mediate to bright signal. Larger cystic locules demonstrate homogeneous T1 low to intermediate signal and T2/short T1 inversion recovery (STIR) hyperintensity. Solid portions and septations usually enhance. Larger cystic locules usually demonstrate rim enhancement.Differential diagnosisKey radiological differencesOther lesions which may appear multilocular including:Giant cell granuloma Internal septa are usually much finer than the ameloblastoma. Also usually seen in the younger population (unless brown tumour related to hyperparathyroidism).Odontogenic myxoma Presence of one or a few straight septa is a feature. Typically demonstrates mild expansion for size.CHAPTER 10Benign Tumours Involving theJaws 154 Atlas of Oral and Maxillofacial RadiologyAneurysmal bone cyst Fine internal septa and typically extremely expansile.Ossifying fibroma When this lesion demonstrates appearance of internal septa, they tend to be larger and less distinct.Keratocystic odonto-genic tumourInternal septa are uncommon and mandibular lesions demonstrate mild expansion for size.Vascular malformation/haemangiomaOften demonstrates serpiginous appearance. Prebiopsy evaluation withMRI should be considered if this suspected.Dentigerous cyst May not be able to radiologically differentiate from the unicystic ameloblastoma in a pericoronal relationship with an unerupted tooth.(a)(b) (c)(d)Substantial buccal lobulated expansion with severe thinning and focal effacements of the cortexWell-defined multilocular appearance with sclerotic borders. Note the coarse curvilinear internal septaSlightly heterogeneous internal appearance largely of soft tissue density with focal lower density regionsRoot resorptionFigure10.1 Ameloblastoma of the left mandible: axial (a), coronal (b) and corrected sagittal (c) bone and axial soft tissue (d) MDCT images. Benign Tumours Involving theJaws 155Well-defined multilocular appearance with well-defined corticated bordersHeterogeneous internal appearance with soft tissue and fluid density regionsExpansion(a)(b) (c)(d)Figure10.2 Ameloblastoma (solid/multicystic) of the left maxilla: axial (a), corrected sagittal (b) and corrected coronal (c) bone and axial soft tissue (d)MDCT images.Substantial buccal expansion for size, with severe thinning and focal effacements of the cortexA particularly large locule of this lesionWell-definedcorticated bordersFigure10.3 Ameloblastoma (solid/multicystic) of the right mandible: axial MDCT image. 156 Atlas of Oral and Maxillofacial RadiologySclerotic bordersRoot resorptionIncidental bone islandsMultilocular internal appearance with multiple small locules and densely sclerotic septaFigure10.4 Ameloblastoma (solid/multicystic) of the left posterior body of the mandible: cropped panoramic radiograph.Root resorptionSubstantial expansion with severe thinning and likely effacement of the cortexWell-defined corticated bordersTooth displacementFigure10.5 Unicystic ameloblastoma of the left posterior mandible: cropped panoramic radiograph. The large locule with buccal expansion and cortical effacement. The lesion remains contained (soft tissue window)Multilocular (multicystic/solid) component. Note the expansion seen in the axial imageOne of the locules is substantial-ly larger than the others Overall soft tissue density appearance of the more multicystic/solid componentInternal fluid attenua-tion of the large locule(a)(b)(c)(d)Figure10.7 Ameloblastoma (solid/multicystic) of the right body of the mandible (also refer to MRI of this case in Figure 10.6): MDCT; corrected sagittal (a), corrected coronal (b) and axial (c) bone and axial soft tissue (d) images.Figure10.6 Ameloblastoma (solid/multicystic) of the right body of mandible (also refer to MDCT of this case in Figure 10.7): MRI; axial STIR (a), corrected sagittal STIR (b), axial T1 postgadolinium fat‐saturated (c) and corrected sagittal T1 (d) images.Heterogeneous intermediate to increased signal of the solid/multicystic componentHomogeneous hyperintense fluid of the larger cystic loculeEnhancement of the solid/multicystic componentRim enhancement of the larger cystic loculeHeterogeneous low to intermediate signal of the solid/multicystic componentHomogeneous intermediate signal of the enlarged cystic locule(a)(b)(c)(d) 158 Atlas of Oral and Maxillofacial RadiologyMultiple small foci of multilocular lesions. The locules are typically small with particularly sclerotic borders(a)(b)Figure10.9 Recurrent ameloblastoma of a right mandibular fibular graft: axial MDCT images (a,b).Figure10.8 Unicystic ameloblastoma of the left posterior mandible: coronal (a), axial (b) and corrected sagittal (c) MDCT images.Root resorptionInferiorly displaced mandibular canal with effacement of the superior borderSubstantial expansion with lobulated appearance. There is severe thinning and focal effacements of the cortex(a)(b)(c) Benign Tumours Involving theJaws 15910.2 Calcifying epithelial odontogenic tumour (Figure10.10)• Synonyms: Pindborg tumour, CEOT.• Rare locally invasive epithelial odontogenic tumour with amyloid‐like material where there may be calcific foci.• Asymptomatic until expansion is noted.• More commonly seen in the posterior mandible, many associ-ated with unerupted teeth.• Surgical excision. This lesion is considered less aggressive than the ameloblastoma but postsurgical radiological review over an extended period is recommended.Radiological features• MDCT demonstrates more features than CBCT.• Variable presentation: ◦may be unilocular or multilocular ◦may demonstrate substantially variable internal calcifications ◦borders are also variable, ranging from well‐defined cortex to poorly defined destructive margins.• May displace teeth.Differential diagnosisKey radiological differencesMay resemble unilocu-lar lucent lesions such as cystic lesions, multi-locular lesions or lesions which demonstrate internal calcificationsThe more common location of the calcifying epithelial odontogenic tumour (CEOT) in the posterior mandible, associated with an unerupted tooth, may be a useful feature.Subtle internal opacity, more apparent in the soft tissue windowDestructive lesion with enhancing soft tissue mass(a) (b)Figure10.10 Calcifying epithelial odontogenic tumour: axial bone (a) and postcontrast soft tissue (b) MDCT images. 160 Atlas of Oral and Maxillofacial Radiology10.3 Odontoma (Figures10.11–10.14)• Synonyms: compound/complex odontoma, compound/complex composite odontoma, odontome.• Considered to be a hamartoma of odontogenic tissues, with the presence of variable combinations of enamel, dentin, cementum and pulp. Not a true tumour.• Variable morphological appearances, ranging from those con-taining tooth‐like structures (compound) to a more amorphous mix of calcified dental tissues (complex).• Usually identified in the second decade.• Complex odontomas are more commonly seen in the posterior mandible.• Compound odontomas occur more commonly in the anterior maxilla.• Many are associated with unerupted teeth. Often contributes to altered eruption or impaction of adjacent teeth. May con-tribute to the malformation of the adjacent teeth.• Otherwise asymptomatic.• Surgical excision. Does not recur. Occasionally left in situ if small and not affecting the dentition, especially those dis-covered later in life.Radiological features• MDCT or CBCT should be considered.• Opacity of variable internal appearance with surrounding lucent margin (lucent band/zone) and a corticated border.• Internal density is variable, depending on the proportion of the various dental tissues. Tooth‐like structures are seen in the compound variety. The complex odontoma demonstrates a more homogeneous internal appearance with densities varying from dentin/cementum to enamel.• Often affects the position, development and eruption of the adjacent teeth, which are occasionally malformed.Differential diagnosisKey radiological differencesCemento‐osseous dysplasia (COD)Mature lesions may resemble the complex odontoma. CODs are often multiple and the borders are usually sclerotic.Ossifying fibromaOdontomas are usually denser, with variable presence of enamel.Well-defined corticated borders, external to the lucent margin (band/zone)Well-defined narrow lucent margin (band/zone) surrounding the internal opacitiesInternal odontoid density structures resembling multiple malformed teethImpacted ectopically positioned 33Figure10.11 Compound odontoma centred at the 33 region: cropped panoramic radiograph. Benign Tumours Involving theJaws 161Impacted ectopically positioned 36Internal odontoid density opacities which do not demonstrate tooth-like morphologyWell-defined corticated borders, external to the lucent margin (band/zone)Well-defined lucent margin (band/zone) surrounding the internal opacities(a)(b)Figure10.12 Complex odontoma of the left posterior mandible: cropped panoramic radiograph (a) and axial MDCT image (b).Internal odontoid density structures resembling multiple malformed teethSlight compression into the left anterolateral aspect of the incisive canalWell-defined narrow lucent margin (band/zone) surrounding the internal opacitiesWell-defined corticated borders, external to the lucent margin (band/zone)Impacted 21Figure10.13 Compound odontoma centred at the 21 region: axial CBCT image. 162 Atlas of Oral and Maxillofacial RadiologyInternal odontoid density structures resembling multiple malformed teethWell-defined narrow lucent margin (band/zone) surrounding the internal opacitiesWell-defined corticated borders, external to the lucent margin (band/zone)Impacted 22(a)(b)Figure10.14 Compound odontoma of the left anterior maxilla: corrected sagittal (a) and axial (b) CBCT images.10.4 Ameloblastic fibroma (Figure10.15)• A benign mixed odontogenic tumour arising from ectomes-enchymal tissues without formation of the calcified dental tissues.• Rare. Most occur in the first and second decades of life.• Asymptomatic unless large enough to cause expansion or interfere with tooth development/eruption.• Most are seen within the posterior mandibular alveolar process.• Conservative excision/enucleation. Low rate of recurrence.Radiological features• MDCT or CBCT should be considered, rather than 2D radiography.• Well‐defined, usually corticated lesion.• Usually unilocular. May be multilocular, usually when larger.• Larger lesions cause expansion with cortical thinning.• May interrupt tooth development/eruption or displace teeth.Differential diagnosisKey radiological differencesDentigerous cyst May be very difficult to differentiate from a pericoronal ameloblastic fibroma. Less likely to be a dentigerous cyst if the margins are not at the cementoenamel junction (CEJ) or at the root surface within 2–3 mm of the CEJ.Keratocystic odontogenic tumour (KCOT)Within the mandibular body, the KCOT demonstrates limited expansion for size. It is usually lucent internally and usually only demonstrates one or a few septa when large.Ameloblastoma Demonstrates coarser septa than ameloblastic fibroma. Substantial root resorption is a feature.Giant cell granulomaDemonstrates fine internal septa. Larger giant cell granulomas typically demon-strate lobulated expansion with a tendency for substantial tooth root resorption.Aneurysmal bone cystOften extremely expansile, unless small. MRI may demonstrate fluid–fluid levels.Odontogenic myxomaUsually demonstrates a few straight septa internally and limited expansion for size. Benign Tumours Involving theJaws 16310.5 Ameloblastic fibroodontoma (Figures10.16–10.18)• Synonym: AFO.• A benign mixed odontogenic tumour involving ectomesen-chymal tissues with the presence of enamel and dentin. Demonstrates histological features of the ameloblastic fibroma and complex odontoma.• Usually identified in the first and second decades of life.• Most are identified within the alveolar process of the poste-rior mandible, often approximating the alveolar crest.• Often interrupts tooth eruption.• Slow growing and expansile when large.• Conservative excision/enucleation. Recurrence rate is consid-ered to be low.Radiological features• MDCT is likely to demonstrate more features but CBCT may be sufficient.• Well‐defined, usually corticated lesion.• Small lesions are often internally lucent, although some dem-onstrate one or a few opacities. Larger lesions usually present with more internal calcifications, with some of odontoid den-sities. Substantially large lesions may present with substantial internal odontoid calcifications.Differential diagnosisKey radiological differencesAmeloblastic fibromaDifficult to differentiate unless there are internal calcifications.Odontoma An early developing odontoma appears very similar to an ameloblastic fibro‐odontoma (AFO) with internal calcifications. AFO calcifications tend to be smaller and more diffused. Large AFOs demonstrate substantial internal odontoid calcifications similar in appearance to those of an odontoma. However, there are large lucent regions within the lesion in AFOs, usually not seen in odontomas.Corticated lucent lesion interrupting the eruption of 37 Lesion extends beyond 2–3 mm of the cementoenamel junctionFigure10.15 Ameloblastic fibroma, 37: corrected coronal CBCT image. 164 Atlas of Oral and Maxillofacial Radiology(a)(b) (c)Displacement of teeth and interruption of eruptionExpansile lesion with multiple varying density opacities, a few of which are of odontoid densityFigure10.16 Ameloblastic fibro‐odontoma of the right body of the mandible: axial (a) and corrected sagittal (b,c) MDCT images.Displaced 18Substantial internal odontoid densities and large lucent regionsExpansion of the right posterior maxilla, including at the sinus baseFigure10.17 Ameloblastic fibro‐odontoma of the right posterior maxilla: cropped panoramic radiograph.Displaced 18Expansion of the right posterior maxilla, including at the sinus base(a)(b)Substantial internal odontoid densities and large lucent regionsFigure10.18 Ameloblastic fibro‐odontoma of the right posterior maxilla: axial (a) and coronal (b) MDCT images. Benign Tumours Involving theJaws 16510.6 Adenomatoid odontogenic tumour (Figure10.19)• Synonym: AOT.• A benign mixed odontogenic tumour with epithelium arranged in a variety of patterns within a mature connective tissue stroma. This lesion has been considered to be a hamartoma.• Rare. Most occur in the second decade of life. More common in females.• Within bone (central), the follicular type (pericoronal relationship to an unerupted tooth) is more common than the extrafollicular variant. Can occur in soft tissues (peripheral).• Most are seen in the maxillary canine region.• Conservative excision. Rare recurrence.Radiological features• MDCT would demonstrate more features although CBCT may suffice.• Well‐defined corticated lesion.• Some may be lucent but most demonstrate variable internal calcifications. Subtle calcifications are more likely to be identi-fied on MDCT, especially in the soft tissue window.• Larger lesions will often displace teeth and may expand and thin the jaw cortices.Differential diagnosisKey radiological differencesCalcifying cystic odontogenic tumourDifficult to differentiate as this lesion also tends to occur anteriorly.Ameloblastic fibro‐odontomaMost commonly seen in the posterior mandible.Calcifying epithelial odontogenic tumourMost commonly seen in the posterior mandible.Dentigerous cyst Less likely to be a dentigerous cyst if the margins are not at the CEJ or at the root surface within 2–3 mm of the CEJ. Dentigerous cysts are almost always completely lucent– occasionally, long‐standing dentigerous cysts or those exposed tothe oral cavity may demonstrate internal calcifications.Keratocystic odontogenic tumourCan appear similar to the adenomatoid odontogenic tumour (AOT) which is internally lucent.Expansile corticated lesion occupying much of the maxillary sinus.Note displacement of the premolarInternal opacities(a)(b)Figure10.19 Adenomatoid odontogenic tumour of the right maxilla: axial (a) and coronal (b) MDCT images. 166 Atlas of Oral and Maxillofacial Radiology10.7 Calcifying cystic odontogenic tumour (Figure10.20)• Synonyms: CCOT, calcifying odontogenic cyst (COC), Gorlin cyst.• Rare odontogenic tumour with spectrum of presentations, ranging from solid to cystic varieties and, extremely rarely, a more aggressive variant. Some authors consider this entity as a cystic tumour with calcifying potential, since most pre-sent as such.• Most commonly seen in the anterior segments of the jaw, especially the maxilla.• May be associated with an impacted tooth.• Sometimes associated with odontomas. Association with other odontogenic tumours is extremely rare.• Surgical enucleation. Recurrence is rare.Radiological features• MDCT would demonstrate more features although CBCT may suffice.• Unilocular expansile lesion.• Borders range from being corticated to ill defined.• Usually largely lucent with variable internal calcifications. Some cases may not demonstrate internal calcifications. Subtle calcifications are more likely to be identified on MDCT, especially in the soft tissue window.• Displaces teeth and resorbs roots.Differential diagnosisKey radiological differencesDentigerous cyst Usually does not demonstrate internal calcifications. However, calcifying cystic odontogenic tumours may not demonstrate internal calcifications. Also, long‐standing dentigerous cysts or those exposed to the oral cavity may occasionally demonstrate internal calcifications.Other cyst‐like lesions which demonstrate internal calcifications, such as AFO, AOT and CEOTCan be difficult to differentiate, especially the AOT, which tends to occur anteriorly. AFOs and CEOTs usually present posteriorly.Apart from the peripheral calcifications, this lesion is otherwise internally of fluid attenuationSubtle internal calcifications peripherally are difficult to appreciate in the bone window, but are much more obvious in the soft tissue window. This may not be demonstrated on a CBCT scan(a)(b)OdontomaRootresorptionWell-definedexpansile lesionwith corticated bordersFigure10.20 Calcifying cystic odontogenic tumour with odontoma of the right maxilla: axial soft tissue (a) and bone (b) MDCT images. Benign Tumours Involving theJaws 16710.8 Odontogenic myxoma (Figures10.21 and10.22)• Synonyms: myxoma, myxofibroma.• A benign odontogenic tumour characterised by the presence of stellate and spindle‐shaped cells and collagen fibres in an abundant myxoid/mucoid matrix.• Usually asymptomatic until larger, when there may some expansion and/or discomfort.• More commonly seen within the body of the mandible, most common in the posterior segment.• Surgical excision/resection beyond radiologically identified margins.• Relatively high recurrence rate. This is related to the gelatinous nature of this lesion, which extends into the adjacent marrow spaces. Postsurgical radiological review is recommended.Radiological features• MDCT demonstrates more features and is the preferred technique but CBCT may be sufficient for some cases. Further characterisation with MRI may be useful, considered by some to be an important modality, in combination with MDCT.• Usually presents as a well‐defined, corticated, multilocular lesion where one or a few of the septa are flat/straight rather than curved. Subtle septa are more likely to be identified on MDCT, especially in the soft tissue window.• Small lesions, especially those occurring pericoronally, may appear as unilocular lucent lesions.• Usually demonstrates relatively limited expansion relative tosize.• May displace teeth, although root resorption is usually not afeature.• MRI: homogeneous intermediate T1 signal; homogeneous high T2/STIR signal. Usually demonstrates gadolinium enhance-ment peripherally and little or no enhancement centrally.Differential diagnosisKey radiological differencesOther lesions with multilocular appearance, including ameloblastoma, giant cell granulomas, aneurysmal bone cysts, keratocystic odontogenic tumour and vascular malformationsThe presence of one or a few flat/straight septa among others is a feature of the odontogenic myxoma. Relatively limited expansion for size is typical but the keratocystic odontogenic tumour also demonstrates this feature. If there is suspicion for a vascular lesion, postcontrast MDCT and MRI must be considered in further evaluation. 168 Atlas of Oral and Maxillofacial RadiologyRelatively straight and sharp internal septa. Note that these septa are not appreciated on the panoramic radiograph(a)(b)(c)(d)Relativelyminorexpansionfor sizeWell-definedcorticatedbordersFigure10.21 Odontogenic myxoma of the left posterior mandible: axial MDCT (a–c) and cropped panoramic radiograph (d) images.Internal attenuation compatible with fluid with proteinaceous materialRelatively minor expansion for sizeWell-defined corticated borderTwo of very few relatively straight internal septa(a)(b)Figure10.22 Odontogenic myxoma of the right mandible: axial soft tissue (a) and bone (b) MDCT images. Benign Tumours Involving theJaws 16910.9 Cementoblastoma (Figure10.23)• Synonym: benign cementoblastoma.• A benign odontogenic tumour largely composed of cementum‐like tissue related to a tooth root. Histological features resemble the osteoblastoma. Some consider that the cementoblastoma is essentially an osteoblastoma occurring at the tooth root apex.• Occurs more commonly in males, most often younger than 25 years old.• Most commonly seen at the mandibular first molar region, centred apically.• Pain is commonly reported. The pulp status of the involved tooth is usually normal.• Surgical excision. When the lesion is completely excised, recurrence is not considered to be common. However, post-surgical radiological review should be considered.Radiological features• Should be examined with MDCT or CBCT.• Well‐defined, largely opaque lesion with a surrounding lucent margin (band) and a corticated/slightly sclerotic border, cen-tred at the apical aspect of a tooth root.• Internal opaque architecture varies from being unstructured to a sunburst/‘spokes of a wheel’ appearance.• Root resorption is commonly seen.• Expansile when sufficiently large.Differential diagnosisKey radiological differencesMature periapical osseous dysplasiaThe lucent margin (band) around the internal opacity is usually less defined and the surrounding opaque border is wider, often more sclerotic in appearance. In addition, root resorption is not commonly seen with periapical osseous dysplasia and these lesions are more likely to be multiple, and are asymptomatic.Bone island No surrounding lucent margin with corticated border. Usually internally homogeneous and root resorption is only occasionally seen.Severe hypercementosisSurrounding periodontal ligament space is usually much narrower and well defined. Usually internally homogeneous and contiguous with the root, with no resorption.Reactive sclerosis related to a periapical inflammatory lesionUsually ill defined with no surrounding lucency. MDCT or CBCT will almost always demonstrate a periapical hypodense/lucent appearance or widening of the apical periodontal ligament space.Irregular root resorption. Note focal region of contiguity of the lesion with the rootBuccal and lingual cortical effacementsExpansile largely opaque heterogeneous lesion with surrounding lucent margin (band/zone). Note the sclerotic borders peripheral to this lucent margin(a)(b)(c)Figure10.23 Cementoblastoma at the 36–37 region: corrected coronal (a), corrected sagittal (b) and axial MDCT images. 170 Atlas of Oral and Maxillofacial RadiologyNONODONTOGENIC BENIGN TUMOURS INVOLVING THEJAWS10.10 Osteoma (Figures10.24–10.29)• A benign, slow‐growing, mature bony prominence at the per-iosteal surface. It remains uncertain if this is a hamartoma or a true benign tumour.• Three types can be seen, consisting of: ◦compact bone (ivory osteoma) ◦cancellous bone ◦combination of compact and cancellous.• Almost exclusively involving membranous bones of the skull and face, most commonly occurring within the paranasal sinuses (especially the frontal sinus and ethmoidal air cells–refer to Chapter19), skull vault and mandible.• When involving the mandible, they most commonly occur at the posterior mandible, often the medial aspect of the ramus or inferior border of the posterior body. They may also be seen at the condyle and coronoid processes.• May be solitary or multiple. Gardner syndrome should be considered when there are multiple osteomas.• Usually asymptomatic, often incidentally identified, unless large with a mass effect or causing clinically detectable asymmetry.• Only require surgical excision if there is a mass effect or there is a cosmetic issue.Radiological features• MDCT or CBCT.• Well‐defined, focal, opaque prominence of variable bony appearance, often with a smooth convex or lobulated sur-face. Usually sessile in morphology although sometimes peduculated.• Internally varies from being homogeneous and isodense with cortical bone (ivory osteoma) to those with variable internal cancellous bone appearance and varying thickness of the overlying cortical bone.• Larger osteomas displace the adjacent soft tissues. Those occurring within the paranasal sinuses potentially distort the sinuses and may contribute to occlusion or narrowing of drainage pathways.Differential diagnosisKey radiological differencesOsteochondroma of the mandibular condyle and coronoid processOsteochondromas demonstrate more irregular morphology with more heterogeneous, sometimes sclerotic, internal appearances.Sessile bony prominence with smooth periosteal surface Internally homogeneous and isodense with cortical bone(a) (b)Figure10.24 Osteoma at the inferior body of the right mandible: corrected sagittal (a) and coronal (b) MDCT images. Benign Tumours Involving theJaws 171Sessile bony prominence with smooth periosteal surfaceInternally homogeneous, isodense and contiguous with the medial cortical bone(a) (b)Figure10.25 Osteoma at the medial aspect of the left mandibular ramus: axial (a) and coronal (b) CBCT images.Internally homogeneous and hypodense to cortical boneSessile bony prominence with smooth periosteal surface. The appearance of the overlying cortex is essentially normalFigure10.26 Osteoma at the inferior left angle of the mandible: corrected sagittal CBCT image.Internally homogeneous and isodense with cortical bone(a) (b)Bony prominence with pedunculated morphology and smooth periosteal surface Figure10.27 Osteoma at the inferior anterior mandible: corrected sagittal (a) and coronal (b) MDCT images. 172 Atlas of Oral and Maxillofacial RadiologyBony prominences with sessile morphology and smooth periosteal surfaces. Internally homogeneous and isodense with cortical bone (a)(b)(c)Figure10.28 Maxillary, ethmoidal and sphenoidal osteomas: CBCT images of three different cases. Maxillary osteoma–coronal image (a). Ethmoid osteoma–axial image (b). Sphenoid osteoma–axial image (c).Bony prominence with sessile morphology and smooth periosteal surface. Internally homogeneous and isodense with cortical boneFigure10.29 Osteoma of the right external auditory canal: axial MDCT image. Benign Tumours Involving theJaws 17310.11 Gardner syndrome (Figures10.30–10.32)• Synonym: familial colorectal polyposis.• A rare autosomal dominant syndrome characterised by multiple intestinal polyps. Other features include osteomas of the skull and facial bones, epidermoid cysts, fibromas, desmoid tumours and a number of other tumours.• High propensity for the intestinal polyps to undergo malig-nant change at an early age.• With the jaws, there may be multiple osteomas and dental anomalies, including multiple unerupted teeth and supernumerary teeth. Multiple bone islands have also been seen. Multiple odontomas have also been described.• Osteomas may develop earlier than the colonic polyps. The jaw features may contribute to early diagnosis.Radiological features within thejaws• There may be multiple osteomas and dental anomalies. Multiple bone islands have also been seen. There may be multiple odontomas. Note that these entities may be present and unrelated to Gardner syndrome.Osteoma SupernumerarytoothImpacted 23 Bone islandFigure10.30 Gardner syndrome: panoramic radiograph. Multiple osteomas, bone islands and dental anomalies.OsteomasOsteoma Maxillary boneislandsMultiple mandibular bone islands(a) (b) (c)Figure10.31 Gardner syndrome: axial (a,b) and corrected coronal (c) MDCT images. 174 Atlas of Oral and Maxillofacial Radiology10.12 Osteochrondroma• Refer to Chapter1810.13 Schwannoma (within thejaws) (Figure10.33)• Synonym: neurilemmoma.• A benign tumour of the Schwann cell, usually well encapsu-lated. Belongs to the group of nerve sheath tumours (refer to Chapter20).• May arise from any peripheral nerve with Schwann cells, including the cranial nerves. When it affects the trigeminal nerve, it is most commonly seen at the skull base. May also occur in patients with neurofibromatosis type 2.• Within the jaws, it most commonly affects the mandibular division of the trigeminal nerve.• Asymptomatic until large enough to affect nerve function, when there may be pain or other sensory changes.Radiological features (when seen within thejaws)• Expansile, corticated lucent lesion with mass effect, including displacement of teeth, root resorption and cortical effacements.• In the mandible, smaller lesions demonstrate focal corticated expansion of the mandibular canal and/or mental/mandibular foramina. Classically, it demonstrates a fusiform morphology, although this is not always seen.• MRI should be considered when a schwannoma is suspected: typically T1 isointense with brain; high T2 signal; homogene-ous gadolinium enhancement.Differential diagnosis (for lesions within thejaws)Key radiological differencesVascular malformations/haemangiomasUsually demonstrates serpiginous or multilocular appearances.Malignant lesions within the mandibular canalUsually demonstrates destruction of the canal borders and the widening of the canal is usually more irregular.OsteomaMentalforamenFigure10.32 Gardner syndrome: axial MDCT image. Benign Tumours Involving theJaws 17510.14 Osteoblastoma• A rare benign bone tumour which produces osteoid tissue and primitive woven bone. ◦Very similar to the osteoid osteoma. Many consider that the osteoblastoma represents a larger osteoid osteoma. ◦Some consider the cementoblastoma as an osteoblastoma centred at a tooth root apex.• Histological differentiation from the low‐grade osteogenic sarcoma can be challenging.• Rarely seen in the jaws, more commonly in the mandible than the maxilla. Most commonly occurs in the spine and long bones. Also in flat bones.• More common in males. Most commonly presents in the second to third decades of life.• Most present with dull pain which is usually not worse at night. Not usually relieved with nonsteroidal anti‐inflammatory drugs. Swelling is noted when sufficiently large.• Surgical excision, usually with a wide margin. May recur.• Postsurgical radiological review is recommended. The possi-bility of incorrect histological diagnosis (osteosarcoma) should be considered.Radiological features• MDCT is recommended. CBCT may be insufficient. MRI may be useful although it often overestimates the lesion.• Variable radiological presentation: ranges from lytic lesions to variable internal opaque appearances.• Internal opacities demonstrate a variety of patterns, ranging from coarse septum‐like architecture to more amorphous appearances. There is often a lucent margin (band/zone) sur-rounding the internal opaque structure(s).• Borders can be ill defined or well demarcated, even corticated.• Expansile and displaces teeth when sufficiently large.• May be associated with a soft tissue mass.Differential diagnosisKey radiological differencesOsteoid osteoma Smaller but otherwise very similar in appearance.Cemento‐osseous dysplasiaCan be similar in appearance. Osteoblastoma demonstrates more tumour features.Osteogenic sarcomaMore aggressive malignant features, including destruction of cortical bounda-ries and invasion of the adjacent structures. This malignancy is often associated with a more prominent soft tissue mass.(a)(b) (c)Expansile lucent lesion with cortical effacements. Note the involvement of the maxillary sinus, nasal cavity and orbitHeterogeneous internal appearance of variable densitiesFigure10.33 Schwannoma of the right maxilla: coronal (a) and axial (b) soft tissue and axial bone (c) MDCT images. 176 Atlas of Oral and Maxillofacial Radiology10.15 Osteoid osteoma (Figure10.34)• A rare benign bone tumour which is considered by many to be a smaller variant of the osteoblastoma.• More common in males.• Usually seen in children and younger adults.• Usually presents with nocturnal pain. Usually relieved with nonsteroidal anti‐inflammatory drugs. There may be associated soft tissue swelling.• Very rarely seen in the jaws. Most commonly seen in the long bones of the limbs, especially the femur.Radiological features• MDCT is recommended. CBCT may be insufficient.• Usually presents as a well‐defined lesion with sclerotic mar-gins centred at the jaw cortex.• Internally, these lesions may be lucent or may demonstrate central opacity.Differential diagnosisKey radiological differencesCemento‐osseous dysplasia Often centred apically ( periapical osseous dysplasia).Cementoblastoma Often centred apically.Lesion centred at the cortex, with sclerotic borders. Note the central opacity with surrounding lucencyFigure10.34 Osteoid osteoma of the left premaxilla. History of nocturnal unexplained pain: axial MDCT image. Benign Tumours Involving theJaws 17710.16 Desmoplastic fibroma (Figure10.35)• Extremely rare benign fibrous bone tumour which is locally destructive. Metastases have not been reported.• Demonstrates slim fibroblasts within an abundant collagen fibre matrix. Often histologically difficult to differentiate from other fibrous‐type lesions. Of particular concern is differentiating these lesions from low‐grade fibrosarcomas. Some consider these lesions as the bony equivalent of the soft tissue desmoid tumours.• Most commonly seen in the jaws, pelvis and femur. In the jaws, it most commonly occurs within the posterior mandible.• Usually presents with swelling and associated dysfunction. Sometimes with pain.• Aggressive surgical excision/resection. High recurrence rate. Postsurgical radiological review is recommended.Radiological features• MDCT is the technique of choice over CBCT. MRI may be useful in further characterisation.• Ill‐defined lesion with aggressive borders, not typical of most benign tumours. Some lesions may be largely well defined but there are usually one or a few regions where the borders are more aggressive and ill defined in appearances.• Internally, small lesions may be lucent but larger lesions usu-ally demonstrate a multilocular appearance with coarse and irregular septa. One or a few of these septa may demonstrate an angular configuration.• There is often destruction of the jaw cortex with extension into the soft tissues.• MRI: low T1 signal; foci of high T2 signal with surrounding intermediate signal; heterogeneous gadolinium enhancement.Differential diagnosisKey radiological differencesFibrosarcoma The difficulty is often associated with the aggressive appearance of the borders of the desmoplastic fibroma. The appearance of coarse internal septa, especially if there are one or a few which demonstrate an angular appearance, favours the desmoplastic fibroma.Other multilocular lesionsThe aggressive features of the desmoplastic fibroma borders are not seen in other benign lesions with multilocular appearances. Coarse internal septa of the desmoplastic fibroma, especially the presence of one or a few which demonstrate an angular appearance, may be helpful.Thick coarse angular septumWhile the border is largely relatively well defined, there is focal destruction of the inferior cortex(a) (b)Figure10.35 Desmoplastic fibroma of the inferior body of the right mandible: cropped panoramic radiograph (a) and axial MDCT image (b).

Related Articles

Leave A Comment?

You must be logged in to post a comment.