Differential diagnosis of lesions of variable radiopacity in the jaws

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Differential diagnosis of lesions of variable radiopacity in the jaws

As explained in Chapter 25, a variety of conditions that can affect the jaws are radiopaque relative to the surrounding bone, although the degree of opacity can be very variable. A step-by-step guide, similar to that suggested for radiolucent lesions in Chapter 26, is outlined to emphasize the importance of a methodical approach when producing a differential diagnosis. The suggested approach is summarized in Fig. 27.1. Although most lesions are still detected using plain radiographs, this process can be greatly facilitated in many cases if advanced imaging modalities, described in Chapters 16 and 18, such as computed tomography (CT), cone beam CT or magnetic resonance (MR) are available.

Fig. 27.1 Step-by-step guide to the differential diagnosis of radiopacities.

Table 27.1

Classification of the more common lesions that can present as variable radiopacities in the jaws

Abnormalities of the teeth
Unerupted and misplaced teeth including supernumeraries
Odontomes — Compound — Complex (see odontogenic tumours)
Root remnants
Hypercementosis
Conditions of variable radiopacity affecting the bone
Developmental	Exostoses including tori — mandibular or palatal
Inflammatory	Low grade chronic infection — sclerosing osteitis Osteomyelitis — sequestra; involucrum formation

Tumours
Odontogenic (late stages)	Calcifying epithelial odontogenic tumour (CEOT) Ameloblastic fibro-odontoma Adenomatoid odontogenic tumour (AOT) Calcifying cystic odontogenic tumour (calcifying odontogenic cyst) Cementoblastoma Odontomes — Compound — Complex
Non-odontogenic	Benign — Osteoma — Chondroma Malignant — Osteosarcoma — Osteogenic secondary metastases
Bone-related lesions
Osseous dysplasias (Fibro-cemento-osseous lesions) (late stages)	Periapical osseous dysplasia Focal osseous dysplasia Florid osseous dysplasia Familial gigantiform cementoma
Other lesions	Ossifying fibroma Fibrous dysplasia
Bone diseases	Paget’s disease of bone Osteopetrosis
Superimposed soft tissue calcifications
Salivary calculi
Calcified lymph nodes
Calcified tonsils
Phleboliths
Calcified acne scars
Foreign bodies
Intra-bony
Within the soft tissues
On or overlying the skin

Step V

Compare the radiological features of the unknown opacity with the typical radiological features of these possible conditions. Then construct a list showing, in order of likelihood, all the conditions that the lesion might be. As mentioned in Chapter 26, this list forms the radiological differential diagnosis.

The typical radiographic features of the important radiopacities are described below using a similar style to that adopted in Chapter 26. It must be emphasized that this is a simplified approach and that most lesions can produce a variety of appearances.

Typical radiographic features of abnormalities of the teeth

Unerupted or misplaced teeth including supernumeraries (Fig. 27.2)

Radiopacities caused by unerupted or misplaced teeth and supernumeraries are readily identifiable as such radiographically, by their characteristic shape and radiodensity.

Fig. 27.2 Examples of opacities caused by unerupted teeth. A Panoramic radiograph showing the typical appearance of unerupted and misplaced wisdom teeth (arrowed) – are positioned transversely. B Periapical showing a conically shaped mesiodens (arrowed) between . Density, shape and outline confirm that the opacity is composed of dental tissue.

Odontomes

Although both compound and complex odontomes are more accurately classified as epithelial odontogenic tumours with odontogenic ectomesenchyme showing dental hard tissue formation (WHO Classification 2005), they are often also described as dental developmental anomalies (see Ch. 24).

Compound odontome

This odontome is made up of several small tooth-like denticles. The miniature tooth shapes are of dental tissue radiodensity, with a surrounding radiolucent line (Fig. 27.3).

Complex odontome

This odontome is made up of an irregular, confused mass of dental tissues bearing no resemblance in shape to a tooth. The enamel content provides the dense radiopacity, suggestive of dental tissue and the mass is surrounded by a radiolucent line (Fig. 27.4).

Root remnants (Fig. 27.5)

Deciduous and permanent root remnants remaining in the alveolar bone, following attempted extraction, are common. The site, shape and density make radiographic identification relatively simple. Additional diagnostic radiographic features include the surrounding radiolucent line of the periodontal ligament shadow and sometimes evidence of a root canal.

Fig. 27.5 Periapical showing opacities (arrowed) either side of root caused by the root remnants of the deciduous .

Hypercementosis (Fig. 27.6)

The formation of excessive amounts of cementum, usually around the apical portion of the root, is common. The cause is unknown, but it is sometimes seen in Paget’s disease of bone and is then typically craggy and irregular. Diagnostically hypercementosis is not a problem – the resultant opacity being part of the tooth root and producing an alteration to the root outline.

Fig. 27.6 Periapical showing early hypercementosis affecting (arrowed).

Typical radiographic features of conditions of variable opacity affecting bone

Developmental

Exostoses, including tori (mandibular or palatal)

Exostoses are small, irregular overgrowths of bone sometimes developing on the surface of the alveolar bone. They consist primarily of compact bone and produce an ill-defined radiopacity when superimposed over the bulk of the alveolar bone. Usually two views are required to establish the exact site (see Fig. 27.7).

Fig. 27.7 A 3-D volume rendered CBCT image showing a large palatal exostosis (palatal torus) (arrowed). B Periapical of showing ill-defined areas of radiopacity (arrowed) overlying the teeth. C Lower 90° occlusal of the same patient showing the large irregular exostoses (mandibular tori) on the lingual aspect of the mandible (arrowed).

Specific exostoses develop in particular sites and are often bilateral:

• Torus mandibularis – lingual aspects of the mandible, in the premolar/molar region

• Torus palatinus – either side of the midline towards the posterior part of the hard palate.

Tumours

Calcifying epithelial odontogenic tumour (CEOT or Pindborg tumour) (Fig. 27.8)

Defined by the WHO as a locally invasive epithelial odontogenic neoplasm, characterized histologically by amyloid material that may become calcified.

Fig. 27.8 A Right side of a panoramic radiograph showing a calcifying epithelial odontogenic tumour in the maxilla (arrowed) associated with the unerupted . There are obvious areas of calcification within the lesion. B Part of a panoramic radiograph showing another CEOT (arrowed) associated with the unerupted lower left canine, with only faint internal calcification. C Right side of a panoramic radiograph showing a poorly defined calcifying epithelial odontogenic tumour (arrowed) associated with the unerupted molar. D Lower 90° occlusal of the same patient showing the expansive, multilocular nature of the lesion and the discrete internal calcifications.

• Age: 20–60-year-old adults.

• Frequency: Rare – approximately 1% of all odontogenic tumours.

• Site: —Molar/premolar region of the mandible

— Maxilla occasionally.

• Shape: — Unilocular or multilocular

— Usually round

— Often associated with an unerupted tooth, particularly .

• Outline: —Variable definition, frequently scalloped

— Variable cortication.

• Radiodensity: —Radiolucent in 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.

• Effects: —Adjacent teeth sometimes displaced, sometimes resorbed

— Expansion of the cortical bone.

Ameloblastic fibro-odontoma (Fig. 27.9)

These rare, unilocular or multilocular odontogenic tumours resemble closely 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.

Fig. 27.9 Oblique lateral showing a large expansive ameloblastic fibro-odontoma (arrowed) in the mandible of a 5-year-old child. The internal calcification is comparable to tooth tissue and histopathology confirmed the presence of enamel and dentine. Note the unerupted tooth.

Adenomatoid odontogenic tumour (AOT) (Fig. 27.10)

Described by the WHO as being composed of odontogenic epithelium embedded in a mature connective tissue stroma and characterized by slow but progressive growth.

Fig. 27.10 A Part of a panoramic radiograph showing a monolocular adenomatoid odontogenic tumour in the anterior maxilla (arrowed) surrounding the unerupted . Internal calcification is evident. B Periapical of the anterior maxilla showing another adenomatoid odontogenic tumour (arrowed) with internal calcification, associated with an unerupted canine. (Reproduced from *A Radiological Atlas of Diseases of the Teeth and Jaws* with kind permission from the authors R.M. Browne, H.D. Edmondson and P.G.J. Rout.)

• Age: Variable, but 90% develop before the age of 30 with most diagnosed in the second decade.

• Frequency: Rare – approximately 2–7% of all odontogenic tumours.

• Site: — Anterior maxilla – incisor/canine region

— Occasionally anterior mandible.

• Shape: — Unilocular

— Usually round or oval

— Often surrounds an entire unerupted tooth.

• Outline: — Smooth and well defined

— Well corticated.

• Radiodensity: —Initially radiolucent, but small opacities (snowflakes) within the central radiolucency may be seen peripherally as the lesion matures.

• Effects: —Adjacent teeth displaced, rarely resorbed

— Associated tooth often unerupted

— Buccal/palatal expansion.

Calcifying cystic odontogenic tumour (calcifying odontogenic cyst or Gorlin’s cyst) (Fig. 27.11)

As stated earlier, the new name of this lesion reflects its classification by the WHO as an odontogenic tumour, who described it as a benign cystic neoplasm of odontogenic origin characterized histologically by ameloblastoma-like epithelium with ghost cells that may calcify. It presents typically anteriorly in either the mandible or the maxilla as a unilocular, well-defined, well-corticated radiolucency resembling other odontogenic cysts, but, as it develops, a variable amount of calcified material becomes evident, scattered throughout the radiolucency. The opacities can range from small flecks to large masses.

Fig. 27.11 A Periapical showing a well-defined calcifying cystic odontogenic tumour (arrowed) in the mandible with obvious areas of internal calcification. B Periapical showing a calcifying cystic odontogenic tumour (arrowed) in the anterior maxilla. The central incisor is unerupted and there is internal calcification of tooth-like density.

• Age: Variable, reported in patients between 5 and 92 years old.

• Frequency: Rare.

• Site: Mandible or maxilla – anterior or premolar regions, one third associated with an unerupted tooth or odontome.

• Size: Usually small, up to 4 cm in diameter.

• Shape: Variable, but usually unilocular.

• Outline: — Smooth, well defined

— Well corticated.

• Radiodensity: Initially radiolucent but in more advanced stages contains a variable amount of calcified radiopaque material of tooth-like density.

• Effects: —Adjacent teeth usually displaced, causing root divergence, and/or resorbed

— Bony expansion.

Cementoblastoma (Fig. 27.12)

As indicated in Table 27.1, the cementoblastoma is classified by the WHO as an odontogenic tumour which is characterized by the formation of cementum-like tissue in connection with the root of a tooth.

Fig. 27.12 A Periapical showing the typical radiopaque mass at the apex of the of a cementoblastoma, the so-called *golf ball* appearance. The mass is attached to the root and has a thin radiolucent line around it (arrowed). B Part of a panoramic radiograph showing a radiopaque cementoblastoma at the apex of (arrowed).

• Age: Reported in patients between 8 and 44 years old, with a mean age of 20.

• Frequency: Rare.

• Site: Apex of mandibular first permanent molars, occasionally premolars. Exceptionally associated with the primary dentition.

• Size: Variable, but up to 2–3 cm in diameter.

• Shape: —Round or irregular, sometimes described as resembling a golf ball

— Attached to a tooth root.

• Outline: Well defined.

• Radiodensity: —Radiopaque but often surrounded by a thin radiolucent line owing to an outer zone of osteoid.

— Often surrounded by a diffuse area of sclerotic bone.

• Effects: —Attached to the tooth root which is usually obscured as a result of resorption and fusion to the tooth

— If large, may cause localized expansion of the cortical plates.

Osteoma (Fig. 27.13)

Osteomas of the jaws may be located in the medullary bone (endosteal osteoma) or arise on the surface of the bone as a pedunculated mass (periosteal osteoma). They are usually detected in young adults and are typically asymptomatic, solitary lesions. Multiple jaw osteomas are a feature of the rare inherited condition Gardner’s syndrome.

Fig. 27.13 A Oblique lateral of right ramus of the mandible showing a round radiopaque compact osteoma (arrowed). B Part of a PA jaws of the same patient showing the lesion (arrowed) arising from the lateral surface of the mandible confirming a periosteal osteoma. C Periapical showing a periosteal cancellous osteoma (arrowed). D Sagittal CBCT image showing a pedunculated osteoma at the angle of the mandible. E Volume rendered 3-D CBCT image of the same osteoma.

There are two main types:

• Compact – consisting of dense lamellae of bone and including the so-called ivory osteoma occasionally seen in the frontal sinus (see Ch. 31).

• Cancellous – consisting of trabeculae of bone.

Both tumours are uncommon. The type of bone making up the tumour determines the degree of radiopacity.

Osteosarcoma (Fig. 27.14)

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

Fig. 27.14 A Right side of a PA jaws of a 7-year-old child showing an osteosarcoma in the ascending ramus of the mandible. The *sunray* or *sunburst* appearance is evident medially and laterally (arrowed). B Oblique lateral showing a very extensive osteogenic osteosarcoma of the mandible with obvious *sunray* or *sunburst* bone formation. C Left side of a panoramic radiograph showing an irregular, poorly defined area of radiopacity (arrowed) in the body of the mandible. D Lower 90° occlusal of the same patient showing extensive buccal and lingual abnormal bone formation (arrowed) of another osteogenic 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 classical, but rare sun ray or sunburst appearance.

Osseous dysplasias

Periapical osseous dysplasia (Fig. 27.15)

Fig. 27.15 Periapical showing the latter stage of periapical osseous dysplasia. The developing internal calcification is arrowed.

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

• Frequency: Rare.

• Site: Apices of several 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 and 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.

Focal osseous dysplasia (Fig. 27.16)

This usually solitary fibrocemento-osseous lesion occupies a portion of the spectrum between the periapical and florid cemento-osseous dysplasias.

Fig. 27.16 Oblique lateral showing relatively late-stage focal osseous dysplasia in the region of the extraction site (arrowed). An appreciable amount of internal calcification is evident.

• Age: Adults between 40 and 50 years old (typically white women).

• Frequency: Uncommon.

• Site: Any areas of the jaws (dentulous or edentulous), but mainly posterior mandible, and often in extraction sites.

• Size: Small, less than 1.5 cm in diameter.

• Shape: Round, unilocular.

• Outline: — Well defined but irregular

— Not corticated.

• Radiodensity: — Early stage – radiolucent

— Intermediate stage – radiolucent with patchy opacity within the radiolucency

— Late stage – densely radiopaque but often 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. 27.17)

Fig. 27.17 Panoramic radiograph showing the multiple lesions (arrowed) of variable radiodensity of florid osseous dysplasia.

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

• Frequency: Rare.

• 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 2–3 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 within 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 sclerosing osteomyelitis.

Familial gigantiform cementoma

This is a rare familial osseous dysplasia. It is inherited as an autosomal dominant condition and confined almost exclusively to young, 10–20-year-old whites. The lesions characteristically show relatively rapid growth, causing marked facial deformity.

Bone-related lesions

As shown in Table 27.1, the WHO classifies a number of different conditions under the general heading bone-related. Two of these can present as mixed radiolucent/radiopaque lesions in the jaws, including:

• Fibrous dysplasia

• Ossifying fibroma.

Fibrous dysplasia (Fig. 27.18)

Fibrous dysplasia is described by the WHO as a genetically based sporadic disease of bone affecting single or multiple bones. The jaws and other bones in the skull can be affected as well as other bones in the skeleton. The general radiological features of fibrous dysplasia are covered in Chapter 28.

Fig. 27.18 Periapical of the upper right maxilla showing the generalized radiolucency with the fine internal trabeculation of monostotic fibrous dysplasia, giving a *ground glass* appearance. The almost imperceptible junction between abnormal and normal bone is arrowed.

The radiographic features of jaw lesions include:

• Age: 10–20-year-old adolescents.

• Site: Maxilla – usually posteriorly, more commonly than the mandible. Maxillary lesions may spread to involve adjacent bones such as the zygoma, sphenoid, occiput and base of skull.

• Size: Variable and difficult to define.

• Shape: Round.

• Outline: —Poorly defined, with the margins merging imperceptibly with adjacent normal bone

— Not corticated.

• Radiodensity: —Initially radiolucent (but rarely seen clinically at this stage)

— Gradually becomes opaque to produce the typical ground glass, orange peel and finger print appearances resulting from superimposition of many fine, poorly calcified bone trabeculae arranged in a disorganized fashion

— Continuing to become more opaque with age.

• Effects: — Adjacent teeth:

* sometimes displaced but rarely resorbed

* loss of associated lamina dura

— Buccal and lingual alveolar expansion

— Encroachment on, or obliteration of, the antrum

— Involvement of adjacent bones including the base of the skull.

Ossifying fibroma (Fig. 27.19)

This lesion has previously been called cementifying fibroma and cemento-ossifying fibroma but the 2005 WHO classification uses the term ossifying fibroma, which is described as a well-demarcated lesion composed histologically of fibrocellular tissue and mineralizing material of varying appearance.

Fig. 27.19 A Part of a panoramic radiograph of a 9-year-old showing an intermediate stage ossifying fibroma, with fine internal calcifications evident, in the right body of the mandible (arrowed). There is also displacement of the unerupted lower premolars and permanent canine. B Part of panoramic radiograph showing a large ossifying fibroma (arrowed) occupying most of the body of the mandible with considerable internal calcification. C Right side of a panoramic radiograph showing a large mature radiopaque ossifying fibroma (arrowed).

• Age: Variable, but usually in the 2nd–4th decades (particularly women).

• Frequency: Rare.

• Site: Usually posterior mandible, but different variants can affect the maxilla and paranasal sinuses.

• Size: Variable, may grow to several cm in diameter and cause facial asymmetry.

• Shape: — Round

— Unilocular.

• Outline: — Smooth, well defined

— When opaque, usually surrounded by a thin encapsulating radiolucent line

— Usually corticated and circumscribed.

• Radiodensity: — Early stage – radiolucent

— Intermediate stage – radiolucent with gradually increasing internal radiopaque calcified patches

— Late stage – radiopaque zones coalesce to form a densely radiopaque mass with or without a radiolucent periphery.

• Effects: — Adjacent teeth:

* often displaced

* occasionally resorbed

— Expansion of the surrounding bone in all dimensions often demonstrating a downward bowing of the mandibular lower border cortex.

Other important bone conditions

Paget’s disease of bone and osteopetrosis, two generalized conditions that can cause an overall increase in bone radiopacity, are discussed in detail in Chapter 28.

Summary

It is worth repeating that the radiodensity of many of the lesions mentioned in this chapter changes as they mature. During their early stages of development, there may be no evidence of internal calcification, making radiological differential diagnosis more difficult. For revision purposes, Table 27.2 summarizes the main lesions of variable radiodensity that can develop internal radiopaque calcifications and so present with mixed radiolucent/radiopaque appearances.

Table 27.2

Summary of the main lesions that can present with variable radiodensity by developing internal radiopaque calcifications

Tumours

Calcifying epithelial odontogenic tumour (CEOT)

Ameloblastic fibro-odontoma

Adenomatoid odontogenic tumour (AOT)

Calcifying cystic odontogenic tumour

Cementoblastoma

Chondroma

Osteoma

Osteogenic osteosarcoma

Osseous dysplasias

Periapical osseous dysplasia

Focal osseous dysplasia

Florid osseous dysplasia

Familial gigantiform cementoma

Bone-related lesions

Fibrous dysplasia

Ossifying fibroma

Typical radiographic features of soft tissue calcifications

A variety of radiopaque calcifications within the overlying soft tissues can present radiographically. Differential diagnosis is relatively straightforward once the site of the opacity has been determined.

Radiopaque salivary calculi (see Ch. 32)

Submandibular gland calculi (Fig. 27.20) are often radiopaque and develop within the main duct or in the gland itself. Those in the main duct can be superimposed on the alveolar bone producing an opacity apparently within the bone. Stones in the gland present usually below the lower border of the mandible.