Differential diagnosis of radiolucent lesions of the jaws

— Well corticated if long-standing (unless infected) and continuous with the lamina dura of the associated tooth.

• Radiodensity: Uniformly radiolucent.

• Effects: — Adjacent teeth displaced, rarely resorbed

— Buccal expansion

— Displacement of the antrum.

Note: The term buccal bifurcation cyst is used to describe an inflammatory odontogenic cyst that develops on the side of a molar tooth in relation to a buccal enamel spur or pearl.

Residual radicular cyst (Fig. 26.3)

This term refers to a radicular (dental) cyst remaining after the causative tooth has been extracted.

Fig. 26.3 Part of a panoramic radiograph showing two residual radicular cysts (arrowed), one in the maxilla and one in the mandible.

• Age: Adults, over 20 years old.

• Site: Apical regions of the tooth-bearing portion of the jaws.

• Size: Variable, usually 2–3 cm in diameter.

• Shape: — Round

— Usually well corticated.

• Effects: —Adjacent teeth displaced, rarely resorbed

— Buccal expansion

— Displacement of the antrum.

Developmental odontogenic cysts

Lateral periodontal cyst (Fig. 26.4)

The diagnosis of this rare developmental cyst should be reserved for a cyst in the lateral periodontal region that is not an inflammatory cyst or an atypical odontogenic keratocyst. It is thought to develop from either the cell rests of the dental lamina or from remains of the reduced enamel epithelium on the lateral surface of the root.

Fig. 26.4 Periapical showing a typically small lateral periodontal cyst (arrowed) between the and . Although the adjacent premolar was restored, it was vital and symptom free.

• Age: Adults over 30 years old.

• Frequency: Rare.

• Site: Lateral surface of the roots of vital teeth in the lower canine/premolar region or upper lateral incisor region.

• Size: Small, less than 1 cm in diameter.

• Shape: —Unilocular, very occasionally multilocular

— Round.

— Well defined and corticated.

• Effects: —Adjacent teeth displaced if cyst becomes large, rarely resorbed

— Buccal expansion if large.

Dentigerous (follicular) cyst (Fig. 26.5)

This cyst develops from the remnants of the reduced enamel epithelium after the tooth has formed.

Fig. 26.5 A Part of a panoramic radiograph showing a typical unilocular dentigerous cyst (arrowed) associated with the unerupted and displaced . B Part of a panoramic radiograph showing a unilocular central dentigerous cyst (arrowed) associated with the unerupted and inferiorly displaced . C Right side of a lower 90° occlusal of the same patient showing the typical buccal expansion (arrowed).

• Age: Usually adolescents or young adults, 20–40-year-olds, occasionally the elderly.

• Frequency: About 20% of all cysts.

• Site: Associated with the crown of an unerupted and displaced tooth, typically teeth where eruption is impeded, e.g. and .

• Size: Very variable, cyst suspected if follicular space exceeds 3 mm but may grow to several centimetres in diameter and extend up into the ramus.

• Shape: —Round or oval, typically enveloping the crown symmetrically

— Unilocular

— Three varieties are described depending on the cyst/crown relationship:

* central

* lateral

* circumferential.

— Often well corticated.

• Effects: —Associated tooth unerupted and displaced

— Adjacent teeth:

* displaced

* resorbed in about 50%

* enveloped by large cysts

— Buccal or medial expansion, can be extensive with large cysts causing facial asymmetry and displacement of the antrum.

Note: The term eruption cyst is used to describe a dentigerous cyst when it is in the soft tissues overlying the unerupted tooth.

Odontogenic keratocyst (keratocystic odontogenic tumour) (Fig. 26.6)

Somewhat controversially, in 2005 the WHO Working Group recommended that the odontogenic keratocyst be renamed the keratocystic odontogenic tumour as they felt this name better reflected its neoplastic nature. The WHO now defines this lesion as a benign uni- or multicystic intraosseous tumour of odontogenic origin with a histologically characteristic lining of parakeratinized stratified squamous epithelium with a potentially aggressive, infiltrative behaviour. It is believed to develop from the epithelium of the dental lamina – the cell rests of Serres – instead of the normal tooth which is therefore typically missing from the series. Lesions are typically solitary but multiple odontogenic keratocysts are a feature of nevoid basal cell carcinoma syndrome (Gorlin’s syndrome), which also includes multiple basal cell carcinomas, and skeletal anomalies, e.g. bifid ribs and calcification of the falx cerebri.

Fig. 26.6 A Oblique lateral of the left side of the mandible showing a typically extensive pseudolocular odontogenic keratocyst (arrowed) which has apparently developed instead of . B PA jaws of the same patient showing that it has caused minimal mediolateral expansion (arrowed). C Left side of a panoramic radiograph showing a very large multilocular odontogenic keratocyst (arrowed) occupying almost all the left side of the mandible.

• Age: Very variable, peak incidence between second and third decades.

• Site: —Posterior body/angle of the mandible extending into the ramus

— Anterior maxilla in canine region.

• Size: Variable, but often large in the mandible.

• Shape: —Oval, extending along the body of the mandible with little mediolateral expansion

— Pseudolocular or multilocular.

• Outline: — Smooth and scalloped

— Well defined and corticated.

• Effects: —Adjacent teeth – minimal displacement, rarely resorbed

— Extensive expansion within the cancellous bone

— May cause cortical perforation

— May include crown of by enfolding so resembling a dentigerous cyst.

Non-odontogenic cysts

Nasopalatine duct/incisive canal cyst (Fig. 26.7)

This cyst develops from epithelial remnants of the nasopalatine duct or incisive canal.

Fig. 26.7 A Periapical showing a typical nasopalatine duct cyst (solid arrows) in the midline between the upper central incisors. Note the superimposed shadow of the anterior nasal spine (open white arrows). B Upper occlusal showing a very extensive nasopalatine duct cyst (arrowed) occupying nearly the entire palate. C Lateral view of the same patient showing the expansion of the cyst into the nasal cavity and palate (arrowed).

• Age: Variable, but most frequently detected in middle age (40–60-year-olds).

• Frequency: Most common of all non-odontogenic cysts, affecting about 1% of total population.

• Site: Midline, anterior maxilla just posterior to the upper central incisors.

• Size: Variable, but usually from 6 mm to several centimetres in diameter.

• Shape: —Round or oval (superimposition of the nasal septum or anterior nasal spine may cause the cyst to appear heart-shaped or resemble an inverted tear drop)

— Well corticated (unless infected).

• Radiodensity: Uniformly radiolucent but radiopaque shadows sometimes superimposed.

• Effects: —Adjacent teeth – distal displacement, rarely resorbed

— Palatal expansion (only identifiable if extensive).

Note: Differentiation is sometimes required between a nasopalatine duct cyst and a large normal nasopalatine foramen. Several features need to be considered including:

• Size – if over 6 mm, a cyst is more likely

• Shape – foramina are usually oval or irregular

• Outline – foramina are usually well defined laterally but not all the way round

• Relative radiodensity – a cyst tends to be more radiolucent having resorbed bone.

Bone cysts or pseudocysts

Despite their names – simple bone cyst and aneurysmal bone cyst – these entities are no longer categorized as cysts. In the new WHO Classification they come under the heading of bone-related lesions. They more commonly affect the skeleton and only relatively rarely affect the jaws.

Simple (solitary) bone cyst (Fig. 26.8)

Defined as an intra-osseous pseudocyst, devoid of an epithelial lining and either empty or filled with serous or sanguineous fluid. The aetiology is unknown.

Fig. 26.8 A Oblique lateral of the right side of the mandible of a teenager showing a typical solitary bone cyst (solid arrows) in the body of the mandible. Note the upper border arching up between the roots of the molar teeth (open arrows). B Oblique lower occlusal of the same patient showing no apparent buccolingual expansion (arrowed).

• Age: Children or young adults, peak incidence in second decade.

• Site: Mandible, particularly anteriorly and in the premolar/molar region.

• Size: Variable, up to several centimetres in diameter.

• Shape: — Unilocular

— Irregular, but the upper border arches up between the roots of the teeth.

• Outline: — Smooth and undulating

— Moderately well defined

— Moderately well or poorly corticated.

• Effects: —Adjacent teeth – minimal or no displacement, very rarely resorbed

— Minimal or no expansion of the jaw.

Aneurysmal bone cyst (see Fig. 26.21)

This rare lesion is defined as an expansile osteolytic lesion, often multilocular with histologically blood-filled spaces separated by fibrous septa containing osteoclast-type giant cells and reactive bone. It is categorized as a giant cell lesion and described later.

Typical radiographic features of tumours and tumour-like lesions

Odontogenic tumours

Ameloblastoma (Fig. 26.9)

An aggressive but non-metastasizing tumour originating from remnants of the odontogenic epithelium of the enamel organ or dental lamina. Four main types include:

Fig. 26.9A Part of a panoramic radiograph showing the typical multilocular appearance of a large ameloblastoma at the angle of the mandible, with extensive expansion (solid arrows) and resorption of adjacent teeth (open arrow).

Fig. 26.9B Right side of a panoramic radiograph showing a very extensive ameloblastoma (arrowed) with a less multilocular appearance but still causing considerable expansion and displacement of . C Left side of a panoramic radiograph showing bilocular ameloblastoma (arrowed) distal to the molar. D Part of a panoramic radiograph showing an ameloblastoma in a more unusual anterior position causing displacement of the adjacent teeth. E Lower occlusal of the same patient showing the buccolingual extent of the lesion (arrowed).

• Solid/multicystic type

• Extra-osseous/peripheral type

• Desmoplastic type

• Unicystic type.

Solid/multicystic ameloblastoma

• Age: Adults 30–60 years old.

• Frequency: Rare, but still the most common odontogenic tumour.

• Site: —80% posterior body/angle/ramus of mandible

— Anterior mandible in black Africans.

• Size: Very variable depending on the age of the lesion, may become very large if neglected and cause gross facial asymmetry.

• Shape: —Multilocular, distinct septa dividing the lesion into compartments with large, apparently discrete areas centrally and with smaller areas on the periphery

— Occasionally unilocular in early stages

— Rarely honeycomb or soap-bubble appearance or multicystic.

• Outline: — Smooth and scalloped

• Radiodensity: Radiolucent with internal radiopaque septa.

— Well corticated.

• Effects: —Adjacent teeth displaced, loosened, often resorbed

— Extensive expansion in all dimensions

— Maxillary lesions can extend into the paranasal sinuses, orbit or base of the skull.

Unicystic ameloblastoma

Accounts for 5–15% of all ameloblastomas and is found equally in the mandible and the maxilla. It usually presents as a unilocular radiolucency associated with the crown of an unerupted tooth (peak age: 16 years), or as a unilocular radiolucency at the apices of teeth, resembling a radicular cyst (peak age: 35 years).

Note: Since different ameloblastomas can mimic a large variety of other radiolucent lesions, this possibility must always be borne in mind when formulating a radiological differential diagnosis.

Ameloblastic fibroma (Fig. 26.10)

A rare, benign, mixed odontogenic tumour originating from both the odontogenic epithelium and the connective tissue of the developing tooth germ. Histologically, it consists of odontogenic ectomesenchyme resembling dental papilla and epithelial strands and rests resembling dental lamina and enamel organ. Radiographically these tumours closely resemble ameloblastomas but develop in a younger age group.

Fig. 26.10 A Part of a panoramic radiograph of a 4-year-old child showing a large ameloblastic fibroma in the right maxilla, causing marked expansion (solid arrows) and displacement of the developing first molar (open arrow). (Kindly provided by Mrs J. E. Brown.) B Oblique lateral of another small child showing a multilocular ameloblastic fibroma (arrowed) in the left body of the mandible causing displacement of the developing premolars and expansion of the lower border. C Oblique lateral showing a very extensive ameloblastic fibroma (arrowed) of the right side in a 17-year-old.

• Age: Children and adolescents – mean age 14 years.

• Site: Posterior mandible (usually) or maxillary premolar/molar region.

• Size: Variable.

• Shape: — Multilocular

— Unilocular in the early stages.

• Radiodensity: Radiolucent with internal radiopaque septa if multilocular.

— Well corticated.

• Effects: — Adjacent teeth displaced

— Buccal/lingual expansion of the jaw

— 50% associated with an unerupted or malpositioned tooth.

Other epithelial odontogenic tumours

The other more important epithelial odontogenic tumours, with or without odontogenic ectomesenchyme, that can present as a radiolucency include:

• Calcifying epithelial odontogenic tumour (CEOT) or Pindborg tumour

• Ameloblastic fibro-odontoma

• Adenomatoid odontogenic tumour (AOT)

• Calcifying cystic odontogenic tumour (calcifying odontogenic cyst).

However, as the name of a couple of them suggests, these lesions often develop internal calcifications and more typically present as lesions of variable radiopacity. They are therefore described in detail with appropriate examples in Chapter 27. A brief summary of each is outlined below.

Calcifying epithelial odontogenic tumour (CEOT), Pindborg tumour

This rare odontogenic tumour usually presents in the premolar/molar region of the mandible in 20–60-year-old adults. They can be either unilocular or multilocular, but tend to remain relatively small although they can cause expansion of surrounding cortical bone. They are often associated with an unerupted tooth particularly . The outline of the lesion tends to be of variable definition and cortication but is frequently scalloped. They are often radiolucent in their early stages; then numerous scattered radiopacities usually become evident within the lesion, often most prominent around the crown of any associated unerupted tooth. This appearance is sometimes described as driven snow. Adjacent teeth can be either displaced and/or resorbed (see Fig. 27.8).

Ameloblastic fibro-odontoma

These rare, unilocular or multilocular odontogenic tumours closely resemble ameloblastic fibromas (see Fig. 26.10), and also affect children. However, they are often associated with an unerupted tooth and usually contain enamel or dentine, either as multiple small opacities or as a solid mass (see Fig. 27.9).

Adenomatoid odontogenic tumour (AOT)

Another rare odontogenic tumour, but unusually the most frequent site affected, is the anterior maxilla in the incisor/canine region. Young adults are usually affected. The lesion tends to be unilocular, round or oval, and often surrounds an entire unerupted tooth. When radiolucent in their early stages, they can closely resemble a dentigerous cyst. However, as the lesion matures, small opacities (snowflakes) within the central radiolucency may be seen peripherally. Adjacent teeth are often displaced as the lesion expands but are rarely resorbed (see Fig. 27.10).

Calcifying cystic odontogenic tumour (calcifying odontogenic cyst or Gorlin’s cyst)

The new name of this lesion reflects its classification by the WHO as an odontogenic tumour. It presents typically anteriorly in either the mandible or the maxilla as a unilocular, well-defined, well-corticated radiolucency resembling any other odontogenic cyst. It can affect any age group having been reported in patients from 5 to 92 years old. One-third of cases are associated with an unerupted tooth or odontome. As the lesion matures, a variable amount of calcified material, of tooth-like density, becomes evident scattered throughout the radiolucency. The opacities can range from small flecks to large masses. Adjacent teeth are usually displaced and/or resorbed (see Fig. 27.11).

Odontogenic fibroma (Fig. 26.11)

Controversy still exists as to the concept and definition of the odontogenic fibroma as a distinct lesion. The WHO classify it separately and describe it as a rare neoplasm characterized histologically by varying amounts of inactive-looking odontogenic epithelium embedded in a mature fibrous stroma. Two sub-types are described, thought to develop from different parts of the tooth germ:

Fig. 26.11 Part of a panoramic radiograph showing a round, unilocular, well-defined radiolucency (arrowed) at the apex of which was clinically vital. Histopathology confirmed an odontogenic fibroma.

• Epithelium-poor originating from the dental follicle

• Epithelium-rich originating from the periodontal ligament.

Typically lesions present as cyst-like well defined, unilocular radiolucencies with dense corticated margin. Rarely calcified material may develop internally and adjacent teeth may be displaced.

Odontogenic myxoma (Fig. 26.12)

This intra-osseous neoplasm is characterized histologically by stellate and spindle-shaped cells embedded in an abundant myxoid or mucoid extracellular matrix originating from the odontogenic connective tissue fibroblasts of the developing tooth germ.

Fig. 26.12 A Left side of a panoramic radiograph showing the typical multilocular appearance of an odontogenic myxoma (arrowed) in the body of the mandible. B Right side of a panoramic radiograph showing an extensive odontogenic myxoma (arrowed) with final internal septa. C Part of an upper oblique occlusal showing a multilocular almost *honeycomb* appearance of an odontogenic myxoma (arrowed) in the maxilla.

• Age: Young adults – most diagnosed in the 2nd–4th decades.

• Frequency: Rare, but the third most common odontogenic tumour.

• Site: Posterior mandible or posterior maxilla.

• Size: Variable, but may become very large if untreated.

• Shape: —Multilocular (honeycomb or soap-bubble)

— Occasionally unilocular.

• Outline: — Smooth and often scalloped

— Well defined with variable cortication.

• Radiodensity: Radiolucent with fine internal radiopaque septa or trabeculae often arranged at right angles to one another, producing an appearance sometimes described as resembling the strings of a tennis racket or the letters X and Y.

• Effects: —Adjacent teeth displaced and loosened, occasionally resorbed

— May be associated with a missing or unerupted tooth

— Extensive buccal and lingual expansion with possible cortical perforation when large.

Radiolucent non-odontogenic tumours

Intrinsic primary benign bone tumours

Central haemangioma (Fig. 26.13)

This is a rare, benign tumour that occasionally affects the jaws, particularly the mandible. It is usually regarded as a developmental malformation (hamartoma) of the blood vessels in the marrow spaces, rather than a true neoplasm.

Fig. 26.13 A Part of a panoramic radiograph of an 8-year-old child showing a large central haemangioma occupying most of the body of the mandible (solid arrows). The typical *honeycomb* appearance is evident on the right (open arrows) and there is evidence of root resorption. B Part of a panoramic radiograph showing a unilocular cyst-like haemangioma (arrowed). (Kindly provided by Mr K. Hussain.) These two examples highlight the very variable appearance of this important lesion. C Left side of a panoramic radiograph showing the multilocular *honeycomb* appearance of a large haemangioma in the posterior maxilla (arrowed).

Central haemangioma can present at any age but is usually discovered in adolescents. It can produce a very variable radiographic appearance. These variations are important because of the life-threatening nature of the lesion; they include:

• Most commonly a multilocular, expanding lesion which may be associated with displacement and resorption of associated teeth. The size and number of locules can vary considerably, and, if numerous, can present with a honeycomb appearance.

• A moderately well-defined zone of radiolucency within which the trabecular spaces are enlarged and the trabeculae themselves are coarse and thick and are said to be arranged like a hub or the spokes of a wheel.

• Rarely, a relatively well-defined, round, cyst-like radiolucency – not distinctive in any way.

• Large lesions may cause cortical expansion, occasionally producing the sunray or sunburst appearance.

Intrinsic primary malignant bone tumours

Osteosarcoma (Fig. 26.14)

Rare, rapidly destructive malignant tumour of bone. From a radiological viewpoint, there are three main types:

Fig. 26.14 A Periapical of showing a poorly defined ragged area of radiolucency (arrowed) with resorption of the lateral aspect of root. Biopsy revealed an osteolytic osteosarcoma. B Periapical showing a similar smaller poorly defined area of bone destruction between (arrowed) which was again shown to be an osteosarcoma.

• Osteolytic – no neoplastic bone formation.

• Osteogenic/osteosclerotic – neoplastic osteoid and bone formed.

• Mixed lytic and sclerotic – patches of neoplastic bone formed.

Early features:

• Non-specific, poorly defined radiolucent area around one or more teeth.

• Widening of the periodontal ligament space.

Later features:

• Osteolytic lesion:

– Unilocular, ragged area of radiolucency

– Poorly defined, moth-eaten outline

– So-called spiking resorption and/or loosening of associated teeth

• Osteogenic and mixed lesions:

– Poorly defined radiolucent area

– Variable internal radiopacity with obliteration of the normal trabecular pattern

– Perforation and expansion of the cortical margins by stretching the periosteum, producing the classic, but rare sun ray or sunburst appearance (see Ch. 27)

– Spiking resorption and/or loosening of associated teeth

– Distortion of the alveolar ridge.

Fibrosarcoma and chondrosarcoma

Both of these primary malignant tumours of bone are rare and produce the irregular, poorly defined radiolucent areas often indicative of the rapid bone destruction of malignancy.

Extrinsic primary malignant tumours involving bone

Squamous cell carcinoma (Fig. 26.15)

Squamous cell carcinomas of the oral mucosa directly overlying bone, in their latter stages, often invade the underlying bone to produce a destructive radiolucency.

Fig. 26.15 A Part of a panoramic radiograph of a patient who presented with a large squamous cell carcinoma on the left ventral surface of his tongue and the floor of his mouth. The radiograph shows two areas of poorly defined radiolucency (arrowed) with a ragged or *moth-eaten* appearance. B Left side of a lower 90° occlusal of the same patient showing the bony destruction (arrowed) of the lingual surface of the mandible as the soft tissue tumour invades the bone. C Part of a panoramic radiograph of another patient who presented with a very large squamous cell carcinoma of the floor of the mouth that had penetrated through the mandible (white arrow) causing a pathological fracture. The ragged bone edges are marked with the black arrows.

• Age: Adults over 50 years old.

• Frequency: Rare, but the most common oral malignant tumour.

• Site: Mandible, or maxilla if originating in the antrum.

• Size: Variable.

• Shape: Irregular area of bone destruction often initially saucer-shaped.

• Outline: — Irregular and moth-eaten

— Poorly defined

— Not corticated.

• Radiodensity: Radiolucent, radiodensity dependent on degree of destruction.

• Effects: —Adjacent teeth may be displaced, loosened and/or resorbed or left floating in space

— Destruction of surrounding bone may lead to pathological fracture.

Secondary (metastatic) bone tumours (Fig. 26.16)

Carcinomas from the bronchus, breast, prostate, kidney and thyroid sometimes metastasize to the jaws and produce the typical destructive radiolucency of a malignant lesion (see Ch. 21).

Fig. 26.16 A Right side of a panoramic radiograph showing the typical destructive, *moth-eaten* radiolucency of a malignant lesion (black arrows). Overlying soft tissue involvement is also evident (white arrows). Subsequent investigation showed this to be a secondary metastatic tumour from the breast. B Left side of a panoramic radiograph showing a large irregular destructive secondary metastatic tumour in the ascending ramus (black arrows). There is an associated pathological fracture (white arrows). C Right side of a panoramic radiograph and D PA jaws of the same patient showing a poorly defined radiolucent secondary metastatic deposit, from the lung, presenting centrally in the ramus (arrowed).

• Age: Adults over 40 years old.

• Frequency: Rare, but the second most common malignant tumours of the jaws.

• Site: Usually centrally in the mandible, molar and premolar regions, occasionally at the apex of a tooth.

• Size: Variable, dependent on the length of time the lesion has been present.

• Shape: Irregular area or areas of bone destruction.

• Outline: — Irregular and moth-eaten

— Poorly defined, not corticated.

• Radiodensity: Radiolucent, but some carcinomas from the prostate and breast may be osteogenic and show areas of bone production/sclerosis.

• Effects: —Adjacent teeth may be displaced, loosened and/or resorbed

— Destruction of surrounding bone

— Involvement of overlying soft tissues.

Note: The radiographic appearance, while strongly indicating a destructive malignant lesion, does not enable the distinction between a primary or secondary tumour to be made.

Lymphoreticular tumours of bone (Fig. 26.17)

Multiple myeloma (Fig. 26.17)

Multifocal proliferation of the plasma cell series within the bone marrow, resulting in overproduction of immunoglobulins.

Fig. 26.17 A True lateral skull showing the typical multiple punched-out lesions (arrowed) of the skull vault of multiple myeloma. B Oblique lateral of the left side showing two similar lesions in the mandible (arrowed). C Upper oblique occlusal showing the typical appearance of destructive malignancy of Burkitt’s lymphoma. Almost all normal anatomical structures have been destroyed.

• Age: Adults, middle-aged.

• Frequency: Uncommon.

• Site: Multiple lesions affecting:

— Skull vault

— Posterior parts of the mandible

— Other parts of the skeleton.

• Size: Variable, individual lesions may be several centimetres in diameter.

• Shape: — Round

— Unilocular, though multifocal.

• Outline: — Punched-out

— Well defined, not corticated.

• Radiodensity: Radiolucent.

• Effects: Enlargement and/or coalescence of lesions may lead to pathological fracture.

Others

• Large cell (anaplastic) lymphoma – adults under 40 years

• Burkitt’s (African) lymphoma – children (see Fig. 26.17C)

• Ewing’s tumour – adults under 40 years.

These lymphoreticular tumours are rare and apart from the age group predilection (shown above), they present in a similar, relatively non-specific manner. Radiographically they usually present as expansile, destructive, poorly defined, radiolucent areas – suggestive of malignant disease.

Langerhans cell disease (histiocytosis X)

Langerhans cell disease is used as a broad grouping of three different clinical manifestations of the same disease. All three manifestations produce tumour-like lesions in bone, caused by proliferation of Langerhans cells and eosinophilic leucocytes:

• Solitary eosinophilic granuloma – localized to the skeleton, affecting adolescents and young adults (see Fig. 26.18)

Fig. 26.18 A Oblique lateral of the left side of the mandible showing a well-defined, unilocular, punched-out, radiolucency (arrowed) beneath the inferior dental canal and therefore non-odontogenic, which proved to be an eosinophilic granuloma. B Left side of a panoramic radiograph showing an extensive punched-out destructive eosinophilic granuloma (arrowed) causing the to appear to be *floating in space*. (Kindly provided by Dr J. Luker.)

• Multifocal eosinophilic granuloma (Hand–Schüller–Christian disease) – chronic and wide-spread, begins in childhood but may not be fully developed until early adulthood, 20–30 years

• Letterer–Siwe disease – acute or subacute and widespread, affecting children under three years old.

Radiographically, the bone lesions (in whatever parts of the skeleton are affected) are similar in all three diseases.

• Frequency: Rare.

• Site: Multiple lesions (in multifocal eosinophilic granuloma and Letterer–Siwe disease only) throughout the skeleton, occasionally solitary lesion, affecting:

— Skull vault

— Mandible or maxilla, posteriorly in the alveolar process.

• Size: Small, 1–2 cm in diameter.

• Shape: — Unilocular

— Round.

• Outline: — Smooth

— Relatively well defined

— Not corticated, appears punched-out.

• Radiodensity: Radiolucent.

• Effects: —Adjacent teeth – not resorbed, but the periodontal bone support is sometimes destroyed so that they appear to be floating or standing in space

— No expansion of the surrounding bone.

Note: Appearance not suggestive of malignant disease.

Typical radiographic features of bone-related lesions

Giant cell lesions

Central giant cell lesion (granuloma) (Fig. 26.19)

A relatively rare localized, benign but sometimes aggressive osteolytic proliferation consisting histiologically of fibrous tissue with haemorrhage and haemosiderin deposits, presence of osteoclast-like giant cells and reactive bone formation producing an expansile radiolucent lesion.

Fig. 26.19 Typical appearance of a central giant cell lesion. A Anterior portion of a static panoramic showing the multilocular appearance, expansion (arrowed) and considerable displacement of the adjacent teeth. B Lower 90° occlusal showing the gross buccal and lingual expansion (arrowed) and the scalloped cortical border. C Lower 45° occlusal of another patient showing the appearance of a similar but much smaller central giant cell lesion (arrowed).

• Age: All ages can be affected but usually young adolescents and adults under 30 years old. One-third of cases reported in patients under 20.

• Site: Mandible – all parts particularly premolar/molar region and anteriorly often crossing the midline.

• Shape: Multilocular, may be unilocular in early stages.

• Outline: — Smooth and scalloped

— Well-defined

— Generally not well corticated.

• Radiodensity: Radiolucent, larger lesions have thin internal septa or trabeculae producing the multilocular, or sometimes honeycomb appearance.

• Effects: —Adjacent teeth often displaced, sometimes resorbed

— Surrounding buccal and lingual bone expanded unevenly producing the scalloped border.

Based on their clinical and radiological effects on adjacent structures, central giant cell lesions are sometimes subdivided into two categories:

• Non-aggressive, which exhibit slow-growing, benign behaviour

• Aggressive, which show the typical features of rapidly growing, destructive lesions.

Brown tumours in hyperparathyroidism

The general radiological features of hyperparathyroidism are discussed in detail in Chapter 31. A few patients with this disease, in addition to the generalized decrease in bone density, also develop circumscribed, cyst-like radiolucencies. Histologically and radiologically these individual lesions (so-called brown tumours) are indistinguishable from central giant cell lesions (see earlier).

Cherubism (Fig. 26.20)

This rare disease of the jaws is inherited, usually as an autosomal dominant, but some cases appear spontaneously. Radiologically the lesions resemble closely other giant cell-containing lesions.

Fig. 26.20 A Panoramic radiograph of a 5-year-old boy showing the typical bilateral multilocular lesions of cherubism affecting the mandible (arrowed). B CBCT reconstructed panoramic image showing widespread multiple multilocular lesions of cherubism (arrowed) .

• Age: Children, 2–6 years old.

• Site: — Angle/posterior mandible – bilateral

— Occasionally posterior maxilla – also bilateral.

• Size: Variable, up to several centimetres in diameter, and may fill the whole jaw.

• Shape: — Multilocular

— Bilateral lesions typically symmetrical.

• Radiodensity: Radiolucent with internal radiopaque septa producing a multilocular appearance.

— Well corticated.

• Effects: —Adjacent teeth – gross displacement of deciduous and permanent teeth, occasionally resorbed, deciduous teeth sometimes exfoliated early

— Extensive buccal/lingual expansion

— Encroachment on the antra by maxillary lesions.

Aneurysmal bone cyst (Fig. 26.21)

As stated earlier, despite its name this rare lesion is categorized as a giant cell lesion and is defined as an expansile osteolytic lesion, often multilocular with histologically blood-filled spaces separated by fibrous septa containing osteoclast-type giant cells and reactive bone.

Fig. 26.21 A Left side of a panoramic radiograph showing a very large multilocular aneurysmal bone cyst in the ramus (arrowed). Note the marked expansion and the displacement of . B PA jaws of the same patient showing *ballooning* expansion (arrowed).

• Age: Adolescents and young adults under 30 years old. Peak incidence in the second decade.

• Site: —Body/posterior mandible including the ramus but very rarely the condyle

— Maxilla occasionally.

• Shape: — Unilocular or multilocular

— Faint internal trabeculation may produce a soap-bubble appearance.

— Moderately well defined

— Peripheral cortex usually retained even when large.

• Radiodensity: Radiolucent with evidence of faint, random internal trabeculations.

• Effects: —Adjacent teeth – displaced, rarely resorbed

— Buccal and lingual expansion of the cortex, often marked and described as ballooning or blow-out

— Rarely cortical perforation.

Bone-related lesions – osseous dysplasias

The 2005 WHO Classification, shown in Table 26.1, now categorizes fibro-cemento-osseous lesions as osseous dysplasias and includes four conditions:

• Periapical osseous dysplasia

• Focal osseous dysplasia

• Florid osseous dysplasia

• Familial gigantiform cementoma.

They are all skeletal disorders in which bone is replaced by fibrous tissue which in turn is replaced by bone or mineralized tissue to a varying degree as the lesions age. Thus, in their early stages all the osseous dysplasias can present as cyst-like radiolucencies, although they are only sometimes seen clinically at this stage. It is more common to see them in their later stages when they present as mixed radiolucent/radiopaque lesions with varying degrees of opacity. Two radiolucent examples are shown here (Figs 26.22 and 26.23). The more radiopaque lesions are discussed and illustrated in Chapter 27.

Fig. 26.22 Periapicals of the lower incisors showing the early and intermediate stages of periapical osseous dysplasia. Several, small, discrete radiolucencies are evident at the apices. The more mature lesions at the apices show evidence of internal calcification (open arrows).

Fig. 26.23 Panoramic radiograph showing multiple radiolucent lesions (arrowed) in the mandible of early stage florid osseous dysplasia.

Periapical osseous dysplasia (Fig. 26.22)

• Age: Middle-aged adults (typically black women).

• Site: Apices of vital lower incisor teeth.

• Size: Small, usually only up to 5–6 mm in diameter.

• Shape: — Round, unilocular

— Often multiple.

• Outline: — Variable but usually poorly defined

— Not corticated.

• Radiodensity: — Early stage – radiolucent

— Intermediate stage – radiolucent with patchy opacity within the radiolucency

— Late stage – densely radiopaque but surrounded by a thin radiolucent line.

• Effects: —Adjacent teeth – not displaced, not resorbed, typically vital, with intact periodontal ligament space, but lamina dura may be discontinuous

— No expansion of the jaw.

Florid osseous dysplasia (Fig. 26.23)

• Age: Middle-aged adults (typically black women).

• Site: Widespread, often in all four quadrants (dentulous and edentulous) but associated with the apices of the teeth if present.

• Size: Variable, but individual lesions up to 2 cm in diameter.

• Shape: — Multiple

— Round, but frequently coalesce.

• Outline: — Smooth but lobular

— Moderately well defined but irregular

— Occasionally corticated.

• Radiodensity: —Early stage – multiple radiolucencies

— Intermediate stage – multiple radiolucencies with gradually increasing patchy internal opacities

— Late stage – multiple irregular dense radiopacities with individual lesions, sometimes surrounded by a thin radiolucent line.

• Effects: —Adjacent teeth – not displaced, not resorbed, typically vital

— Occasionally may cause expansion or enlargement of the affected jaw

— Can be associated with low grade osteomyelitis.

Other bone-related lesions

The other bone-related lesions that could present as a radiolucency include:

• Fibrous dysplasia (see Chapters 27 and 28 as more commonly mixed radiodensity)

• Ossifying fibroma (see Chapter 27 as more commonly mixed radiodensity)

• Simple bone cyst (see earlier)

• Stafne’s bone cavity.

Stafne’s bone cavity (Fig. 26.24)

A bone cavity or depression on the lingual aspect of the mandible near the lower border, frequently said to contain aberrant salivary gland tissue.

Fig. 26.24 Right side of a panoramic radiograph showing the typical cyst-like appearance of Stafne’s bone cavity at the angle of the mandible, below the inferior dental canal (arrowed).

• Age: Adults.

• Site: Angle of the mandible, below the inferior dental canal but above or involving the lower border.

• Size: 1–2 cm in diameter, size does not usually alter with age.

• Shape: — Round

• Outline: — Well defined

— Variable cortication.