Fibro‐osseous Lesions of the Jaws










Atlas of Oral and Maxillofacial Radiology, First Edition. Bernard Koong.
© 2017 John Wiley & Sons Ltd. Published 2017 by John Wiley & Sons Ltd.
140
9.1 Fibrous dysplasia (Figures9.1–9.10; also see
Figure 20.17)
Benign genetically based sporadic condition of bone where
there is abnormal remodelling with presence of dysplastic
fibrous tissue and varying amounts of immature bone.
Most common benign bone disorder.
Can be:
Monostotic (one location)–majority of cases.
Polyostotic (multiple locations) – usually identified in
young children. Can be associated with McCune–Albright
syndrome.
Growth of lesion usually ceases at the end of skeletal growth.
May present with painless facial swelling and asymmetry.
Larger lesions may impinge on nerves.
Clinical and radiological diagnosis is often sufficient, without
biopsy. Histological appearances can be ‘fibro‐osseous but
otherwise non‐specific’.
Surgical interventions resulting in exuberant growth in the
younger patient have been reported.
Sarcomatous changes have been reported but generally
considered to be rare.
Radiological features
Best examined with multidetector computed tomography
(MDCT) or cone beam computed tomography (CBCT).
Solitary lesions are almost always limited to one bone.
Borders are often described as ill‐defined, but this is usually a
plain film appearance. These lesions often demonstrate rela-
tively well‐defined borders on MDCT, CBCT and magnetic
resonance imaging (MRI).
Often hyperdense to normal bone but some may present with
focal regions of increased density as well as focal regions
which are hypodense and lucent compared with normal bone.
Classical ground‐glassinternal appearance is most frequently
seen, at least in some regions of the lesion. However, other
internal patterns, including cotton wool, orange peel, cyst‐like
and ‘multilocular’ appearances, are also seen.
Expansion is an important feature, unless the lesion is
extremely small. The expanded bone tends to resemble the
original anatomy. That is, while expanded and slightly
distorted, the general morphology of the structure is pre-
served. For example, expansion at the maxillary sinus base
will elevate this floor, but the concave shape of this floor is
maintained.
There is often thinning and alteration of the cortical archi-
tecture, sometimes with focal regions where the cortex is
absent.
The architecture of the lamina dura of the teeth is often
altered and may be indistinct. Teeth are often displaced.
Root resorption is rare.
Lesions inferior to the mandibular canal will classically deflect
the canal superiorly.
Variable MRI signal pattern is related to the amount and
pattern of bone and fibrous tissue, presence of spindle cells
and haemorrhage. Usually T1 and T2 hypointense. Variable
gadolinium enhancement.
Differential diagnosis
Key radiological differences
Chronic osteomyelitis Demonstrates periosteal
response and sequestra.
Ossifying fibroma More tumour‐like growth and
expansion where the normal
morphology is not preserved.
There may be surrounding
lucent margin.
Osteogenic sarcoma More aggressive bone growth,
usually with spiculation.
Paget disease Usually older age group and
usually bilateral.
CHAPTER 9
Fibroosseous Lesions oftheJaws

Fibro‐osseous Lesions oftheJaws 141
(a) (b)
Expansile lesion with
ground-glass internal
appearance
Relatively well-defined border
seen on MDCT, which appears
ill-defined on the panoramic
radiograph
Cortex altered
and
hypodense
Figure9.1 Fibrous dysplasia: panoramic radiograph (a) and axial MDCT image (b).
Expansile lesion with internal
heterogeneous appearance,
including focal opaque and
lucent regions
Appearance of
relatively ill-defined
border in this view
Figure9.2 Fibrous dysplasia: cropped panoramic radiograph.

142 Atlas of Oral and Maxillofacial Radiology
Well-defined border
Expansile with focal
cortical thinning and
decreased density
Internal ground-glass
appearance, with slight
heterogeneity further
posteriorly
Figure9.4 Fibrous dysplasia: axial MDCT image.
The sinus floor has been
elevated and not visualised
Expansile lesion with
internal homogeneous
ground-glass appearance
Several cortical structures are
altered and no longer visualised in
this view, including the infraorbital
canal and foramen
Figure9.3 Fibrous dysplasia: panoramic radiograph.

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Atlas of Oral and Maxillofacial Radiology, First Edition. Bernard Koong. © 2017 John Wiley & Sons Ltd. Published 2017 by John Wiley & Sons Ltd.1409.1 Fibrous dysplasia (Figures9.1–9.10; also see Figure 20.17)• Benign genetically based sporadic condition of bone where there is abnormal remodelling with presence of dysplastic fibrous tissue and varying amounts of immature bone.• Most common benign bone disorder.• Can be: ◦Monostotic (one location)–majority of cases. ◦Polyostotic (multiple locations) – usually identified in young children. Can be associated with McCune–Albright syndrome.• Growth of lesion usually ceases at the end of skeletal growth.• May present with painless facial swelling and asymmetry. Larger lesions may impinge on nerves.• Clinical and radiological diagnosis is often sufficient, without biopsy. Histological appearances can be ‘fibro‐osseous but otherwise non‐specific’.• Surgical interventions resulting in exuberant growth in the younger patient have been reported.• Sarcomatous changes have been reported but generally considered to be rare.Radiological features• Best examined with multidetector computed tomography (MDCT) or cone beam computed tomography (CBCT).• Solitary lesions are almost always limited to one bone.• Borders are often described as ill‐defined, but this is usually a plain film appearance. These lesions often demonstrate rela-tively well‐defined borders on MDCT, CBCT and magnetic resonance imaging (MRI).• Often hyperdense to normal bone but some may present with focal regions of increased density as well as focal regions which are hypodense and lucent compared with normal bone.• Classical ‘ground‐glass’ internal appearance is most frequently seen, at least in some regions of the lesion. However, other internal patterns, including cotton wool, orange peel, cyst‐like and ‘multilocular’ appearances, are also seen.• Expansion is an important feature, unless the lesion is extremely small. The expanded bone tends to resemble the original anatomy. That is, while expanded and slightly distorted, the general morphology of the structure is pre-served. For example, expansion at the maxillary sinus base will elevate this floor, but the concave shape of this floor is maintained.• There is often thinning and alteration of the cortical archi-tecture, sometimes with focal regions where the cortex is absent.• The architecture of the lamina dura of the teeth is often altered and may be indistinct. Teeth are often displaced. Root resorption is rare.• Lesions inferior to the mandibular canal will classically deflect the canal superiorly.• Variable MRI signal pattern is related to the amount and pattern of bone and fibrous tissue, presence of spindle cells and haemorrhage. Usually T1 and T2 hypointense. Variable gadolinium enhancement.Differential diagnosisKey radiological differencesChronic osteomyelitis Demonstrates periosteal response and sequestra.Ossifying fibroma More tumour‐like growth and expansion where the normal morphology is not preserved. There may be surrounding lucent margin.Osteogenic sarcoma More aggressive bone growth, usually with spiculation.Paget disease Usually older age group and usually bilateral.CHAPTER 9Fibroosseous Lesions oftheJaws Fibro‐osseous Lesions oftheJaws 141(a) (b)Expansile lesion with ground-glass internal appearanceRelatively well-defined border seen on MDCT, which appears ill-defined on the panoramic radiographCortex altered and hypodenseFigure9.1 Fibrous dysplasia: panoramic radiograph (a) and axial MDCT image (b).Expansile lesion with internal heterogeneous appearance, including focal opaque and lucent regionsAppearance of relatively ill-defined border in this viewFigure9.2 Fibrous dysplasia: cropped panoramic radiograph. 142 Atlas of Oral and Maxillofacial RadiologyWell-defined borderExpansile with focal cortical thinning and decreased densityInternal ground-glass appearance, with slight heterogeneity further posteriorlyFigure9.4 Fibrous dysplasia: axial MDCT image.The sinus floor has been elevated and not visualisedExpansile lesion with internal homogeneous ground-glass appearanceSeveral cortical structures are altered and no longer visualised in this view, including the infraorbital canal and foramenFigure9.3 Fibrous dysplasia: panoramic radiograph. Fibro‐osseous Lesions oftheJaws 143While expansile, the overall mandibular morphology is not severely alteredExpansile with internal ground-glass featureAlteration and thinning of corticesFigure9.5 Fibrous dysplasia: coronal MDCT image.Expansion which generally retains the original concave morphology of the palateAlteration of the cortexInternal ground-glass appearanceFigure9.6 Fibrous dysplasia: coronal CBCT image.Focal regions of altered lamina duraWell-defined borderInternal composition essentially homogeneously ground glass, with focal regions of increased densityFigure9.7 Fibrous dysplasia: corrected sagittal CBCT image. Expansion of the sinus wall remains concaveInternal heterogeneous appearance, with increased density and lucent regions of fibrous tissueAlteration of the cortex with focal absenceFigure9.8 Fibrous dysplasia: axial MDCT image.(Courtesy of Koong B. Diagnostic imaging of the periodontal and implant patient. In: Lindhe J, Lang NP, editors. Clinical Periodontology and Implant Dentistry. 6th ed. Wiley Blackwell; 2015. Reproduced with permission from Wiley.)Internal heterogeneous appearance with hyper- and hypodense regionsWhile expansile, the overall maxillary morphology is not severely altered. That is, the concave maxillary morphology laterally, palatally, and at the nasal and maxillary antral bases is essentially maintainedFocal regions of altered and absent sinus cortical floorFigure9.9 Fibrous dysplasia: coronal MDCT image.Internal heterogeneous appearance with lucent regionsSlight superior displacement of the mandibular canalWell-defined sclerotic marginsFigure9.10 Fibrous dysplasia: corrected sagittal CBCT image. Fibro‐osseous Lesions oftheJaws 1459.2 Cementoosseous dysplasia (Figures9.11–9.21)• Benign focal change of normal bone to fibrous tissue and metaplastic bone and/or cementum‐like material.• More common in Black and some Asian subjects and also in females.• Most often identified in the 40 year age group.• Three subtypes have been described: 1 Periapical osseous dysplasia (periapical cemental dysplasia): most frequently seen type. Often multiple and involving mandibular anterior teeth. The term periapical cementoma is now rarely used. 2 Florid osseous dysplasia: often widespread involving the alveolar processes and body of mandible. More often found in Black patients. Note that another widespread form referred to as familial gigantiform cementoma has been described, thought to be much less common than florid osseous dysplasia.3 Focal cemento‐osseous dysplasia: has been considered to be more common in White people.• Diagnosis is often clinical and radiological. Histological appearance is not infrequently ‘fibro‐osseous but otherwise non‐specific’.• Does not require treatment. Potential misdiagnosis for peria-pical inflammatory disease and unnecessary endodontic treatment or extraction.• Potential secondary infection. Examples include: ◦Exposure to oral cavity via residual ridge atrophy at an edentulous site. ◦Inflammatory periodontal bone loss.Radiological features• MDCT or CBCT should be considered unless the appear-ances are definitive on 2D radiography.• Immature lesions are usually lucent, with sclerotic margins.• In time, internal focal opacity(s) appears and increases in size as the lesion matures over years. These opacities are usually homogeneous.• Mature lesions present as opaque lesions demonstrating a surrounding lucent margin (band) with sclerotic borders. Occasionally, they can appear essentially opaque, where the surrounding lucent margin is essentially absent.• Occasionally, these lesions can be internally homogeneous, demonstrating a ground‐glass appearance.• Rarely, simple bone cysts are associated with these lesions (Figure 9.18; also see Figure 8.44). However, residual opaque bone/cementum deposits usually remain present.• The lamina dura of the involved teeth is usually absent or altered but the periodontal space is often preserved. Root resorption is rare.• Expansion is often seen with larger lesions, where the thinned cortices are often largely preserved, although focal cortical absence is not uncommon.• Larger lesions may displace the mandibular canal.Differential diagnosisKey radiological differencesEarly/immature lesionsChronic periapical inflammatory lesionWhen there are no internal opacities, these lesions can be radiologically almost identicalbut cemento‐osseous dysplasia is usually multiple. MDCT or CBCT may demonstrate small or low‐density internal opacities of cemento‐osseous dysplasia, which are not demonstrated on 2D radiography.Mature lesionsBone island No surrounding lucent margin and adjacent trabeculae run into the opacity.Odontoma Internal odontoid structures. Often pericoronal.Cementoblastoma Irregular root resorption. Usually painful.Ossifying fibroma Rarely, these lesions can appear very similar, especially with larger cemento‐osseous dysplasia lesions. The ossifying fibroma has more of a mass effect, especially on the affected dentition. Cemento‐osseous dysplasia is often multiple; ossifying fibroma is a solitary lesion. 146 Atlas of Oral and Maxillofacial RadiologyBuccal expansion with the cortex largely preservedPreserved periodontal ligament spaces. The architecture of the lamina dura is alteredInternally homogeneously opaqueSclerotic bordersLucent margin (band) surrounding the opacity is of variable width, although wider than the lesion depicted in the sagittal image (a)Lucent margin (band) surrounding the opacity is narrower than the case demonstrated in the coronal image (b) as this case (a) is even more mature(a) (b)Figure9.11 Mature periapical osseous dysplasia–two different cases: corrected sagittal (a) and coronal (b) CBCT images.Altered apical lamina dura with preservation of the apical periodontal ligament spaceSclerotic border Internally homogeneously opaqueNarrow lucent margin (band) surrounding the opacity, related to maturity of this lesionFigure9.12 Mature periapical osseous dysplasia: cropped panoramic radiograph. Fibro‐osseous Lesions oftheJaws 147Sclerotic margins41 periapical slightly hypodense focus where the apical lamina dura and periodontal ligament space are still preserved42 periapical hypodense focus. The apical lamina dura is not appreciated. No internal opacities demonstratedFigure9.13 Early periapical osseous dysplasia, 42 and 41: cropped periapical radiograph. Note: The 42 apical appearances are similar to chronic periapical inflammatory lesions. However, MDCT or CBCT would probably demonstrate preservation of the apical periodontal ligament space and the altered architecture of the lamina dura. These techniques may also demonstrate internal calcifications not appreciated on intraoral radiographs.Internally hypodense appearance with foci of varying degrees of increased densities, related to the early-to-moderate maturity of these lesions Sclerotic marginsFigure9.14 Periapical osseous dysplasia: coronal CBCT image. Mental foramenUndisplaced mandibular canal with preserved bordersBuccal expansion with thinned lingual cortexInternally homogeneous with ground-glass appearanceFigure9.15 Periapical osseous dysplasia: corrected coronal CBCT image.Convex elevation of the sinus floorMinimal residual surrounding lucent margin (band)Buccal expansion with thinning and focal absence of the cortexInternally heterogeneous with focal opaque and lucent regionsFigure9.16 Mature focal cemento‐osseous dysplasia: coronal CBCT image.Small focal absence of the labial cortexBuccal expansion with a focal hypodense appearance of the cortexMultiple lesions with varying internal well-defined opacities with surrounding lucent margins (bands) and sclerotic borders Figure9.17 Florid osseous dysplasia: axial CBCT image. Fibro‐osseous Lesions oftheJaws 149Simple bone cyst associated with this lesion. Note the opacity centred at the 36 mesial root apexFigure9.18 Florid osseous dysplasia: panoramic radiograph. There are multiple lesions associated with most of the mandibular teeth and the maxillary second and third molars, with varying well‐defined internal opacities. Note the variable residual surrounding lucencies and the sclerotic margins.Figure9.19 Florid osseous dysplasia: panoramic radiograph. There are multiple lesions centred at the apical regions of 48–37. Note the varying internal opacities which reflect the different stages of maturity of these lesions. Sclerotic margins are demonstrated. 150 Atlas of Oral and Maxillofacial Radiology9.3 Ossifying fibroma (Figures9.22 and9.23)• Synonyms: cemento‐ossifying fibroma, cementifying fibroma, juvenile ossifying fibroma.• Classified, behaves and managed as a benign tumour but often discussed in relation to fibro‐osseous lesions.• Composed of fibrocellular tissue with varying amounts of mineralised bone/cementum‐like material.• Internal histological appearances can resemble fibrous dysplasia and cemento‐osseous dysplasia.• Can be aggressive or indolent, tending to be more aggressive in the younger patient.• More often seen in females.• Much less common than cemento‐osseous dysplasia and fibrous dysplasia.• In the jaws, it is considered to be most common within the pos-terior body of the mandible, although it also presents elsewhere.• Often presents as a painless swelling, sometimes with displacement of teeth.• Usually surgically enucleated. Recurrence is not likely.Figure9.20 Florid osseous dysplasia: panoramic radiograph. There are multiple lesions centred at the apices of most of the mandibular teeth. Note the internal homogeneous opacities with relatively narrow surrounding residual lucent margin (band), related to the degree of maturity of these lesions. The margins are sclerotic.(a) (b) (c) Internal homogeneous opacity with narrow residual surrounding lucent margin (band). Borders are scleroticFocal increased uptakeFigure9.21 Mature focal cemento‐osseous dysplasia: periapical radiograph (a), coronal MDCT (b) and technetium bone scan (c) images. Fibro‐osseous Lesions oftheJaws 151Radiological features• MDCT may demonstrate soft tissue changes, although CBCT is likely to be sufficient for many cases.• Tumour‐like mixed‐density expansile lesion.• Well‐defined borders, which may be corticated. A surrounding lucent margin (band) may be present, possibly only at one or a few aspects of these lesions.• Internal density varies substantially, depending on the amount of mineralised material. It can be essentially lucent. The pattern of the mineralised material also varies, from ground‐glass appearances (similar to fibrous dysplasia) to homogeneous opacities (similar to cemento‐osseous dysplasia).• Variable T1‐ and T2‐weighted MRI signal patterns, related to the varying amounts of fibrous/mineralised tissue and the pattern of the mineralised tissue. Gadolinium enhancement is also variable, from homogeneous enhancement to focal regions of enhancement.• Usually demonstrates tumour‐like mass effect: ◦Displaces anatomic structures such as the mandibular canal, paranasal sinuses and nasal cavity. ◦Displaces teeth with effacement of the lamina dura. May cause root resorption. ◦Expanded jaw cortices are often thinned and altered. The expanded cortices are classically largely preserved, although focal regions of cortical absence may be seen.• Adjacent bone can be sclerotic.Differential diagnosisKey radiological differencesFibrous dysplasia Borders are less well defined and there is no surrounding lucent margin. Expansion is not tumour like, resembling the original anatomy. Root resorption is rare.Cemento‐osseous dysplasia Periapical osseous dysplasia and florid osseous dysplasia are usually multifocal. Less tumour‐like growth, especially in relation to teeth.Multilocular lesions including giant cell lesionsPresence of internal septa.Lesions with internal calcifications, including calcifying cystic odontogenic tumour, adenomatoid odontogenic tumour and the rare calcifying epithelial odontogenic tumour (Pindborg tumour)The internal calcifications of these lesions are usually small.Nasal base and palatal tumour-like expansion. Altered and thinned expanded nasal and palatal cortices with focal absenceTumour-like expansion. Altered and thinned expanded nasal and palatal cortices with focal absenceWell-definedcorticated borderWell-defined lucent margin (band) surrounds the internal opaque appearances, with an adjacent prominentlycorticated borderVariation in internal densityWell-defined border, with adjacent mild sclerosis(a)(b) (c)Figure9.22 Ossifying fibroma: sagittal (a) and coronal (b,c) MDCT images. 152 Atlas of Oral and Maxillofacial Radiology(a) (b)Internal hypodense appearance with small focal increased densitiesFocal effacement of the incisive canal borderRoot resorptionAltered and thinned expanded labial cortex with focal effacementTumour-like expansion. Note the relationship with the residual labial cortex Figure9.23 Ossifying fibroma: corrected sagittal (a) and axial (b) MDCT images.

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