Differential diagnosis of radiolucent lesions of the jaws

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Differential diagnosis of radiolucent lesions of the jaws

Introduction

This chapter is designed to simplify the process of arriving at a radiological differential diagnosis when confronted with a radiolucency of unknown cause on a plain radiograph. This process requires clinicians to follow a methodical step-by-step approach and to know the typical features of the various possibilities. Such a step-by-step guide is suggested and summarized in Fig. 26.1. 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.

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Fig. 26.1 Summary of the step-by-step guide to producing a differential diagnosis.

Unfortunately, most of the lesions encountered share several similar features and often individual conditions can present in many different ways. Thus the summary of features for the more important conditions included in this chapter is an attempt to unravel some of the inevitable confusion. Also, for simplicity, the frequency with which the various lesions present has been divided arbitrarily into common, uncommon and rare. It is hoped and intended that the reader should expand on this short-notes style framework by referring to the suggested reading list.

Step-by-step guide

Step IV

Consider the classification and subdivision of cysts and other similar radiolucencies within each of the other main disease categories, as shown in Table 26.1. This resultant list includes most of the more likely diagnostic possibilities for the unknown radiolucent lesion.

Table 26.1

Classification of the main cysts and tumours and other bone-related conditions that can present as a cyst-like radiolucency (based broadly on the 2005 WHO Classification)

Cysts  
Odontogenic Radicular (dental) cyst
  Residual radicular cyst
  Lateral periodontal cyst
  Dentigerous cyst
  Odontogenic keratocyst (keratocystic odontogenic tumour)
Non-odontogenic Nasopalatine duct / incisive canal cyst
  Bone cysts (see bone-related lesions)
Tumours and tumour-like lesions  
Benign odontogenic Ameloblastoma
(epithelial with mature, fibrous stroma without odontogenic ectomesenchyme) Squamous odontogenic tumour
Calcifying epithelial odontogenic tumour (Pindborg tumour)
  Adenomatoid odontogenic tumour
  Keratocystic odontogenic tumour (odontogenic keratocyst)
Benign odontogenic Ameloblastic fibroma
(epithelial with odontogenic ectomesenchyme, with or without hard tissue formation) Ameloblastic fibro-odontoma
Calcifying cystic odontogenic tumour (calcifying odontogenic cyst)
Benign odontogenic Odontogenic fibroma
(mesenchymal and/or odontogenic ectomesenchyme with or without odontogenic epithelium) Odontogenic myxoma
Malignant odontogenic Odontogenic carcinoma
  Odontogenic sarcoma
Non-odontogenic intrinsic primary bone tumours Benign – Fibroma
 – Chondroma
   – Central haemangioma
   – Neurofibroma
  Malignant – Osteosarcoma
   – Fibrosarcoma
   – Chondrosarcoma
Extrinsic primary tumours involving bone Squamous cell carcinoma
Secondary metastatic bone tumours  
Lymphoreticular tumours of bone Multiple myeloma
  Large cell lymphoma
  Burkitt’s lymphoma
  Ewing’s tumour
Langerhans cell disease Eosinophilic granuloma
(Histiocystosis X) Hand–Schüller–Christian disease
  Letterer–Siwe disease
Bone-related lesions  
Giant cell lesions Central giant cell lesion (granuloma)
  Brown tumour in hyperparathyroidism
  Cherubism
  Aneurysmal bone cyst
Osseous dysplasias Periapical osseous dysplasia
(Fibro-cemento-osseous lesions) Focal osseous dysplasia
(early stages) Florid osseous dysplasia
  Familial gigantiform cementoma
Other lesions Ossifying fibroma
  Fibrous dysplasia
  Simple bone cyst
  Stafne’s bone cavity

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Step V

Compare the radiological features of the unknown radiolucency 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. This list forms the radiological differential diagnosis.

Infection is described elsewhere (apical, Ch. 21, spreading, Ch. 28) and trauma is described in Chapter 29. The rest of this chapter is devoted principally to differentiating between the different cysts – the most common of the remaining categories – and the other lesions that often present as very similar radiolucencies.

Typical radiographic features of cysts

Inflammatory odontogenic cysts

Radicular (dental) cyst (Fig. 26.2)

This inflammatory cyst develops from the epithelial remnants of Hertwig’s root sheath – the cell rests of Malassez.

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Fig. 26.2 A Static panoramic (Panoral) radiograph showing a typical radicular (dental) cyst (arrowed) associated with the non-vital image. B Upper standard occlusal showing a large radicular cyst associated with the root-filled image. C Part of a panoramic radiograph showing a typical unilocular radicular cyst associated with the non-vital image.

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.

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.

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

Dentigerous (follicular) cyst (Fig. 26.5)

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

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Fig. 26.5 A Part of a panoramic radiograph showing a typical unilocular dentigerous cyst (arrowed) associated with the unerupted and displaced image. B Part of a panoramic radiograph showing a unilocular central dentigerous cyst (arrowed) associated with the unerupted and inferiorly displaced image. 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. image and image.

• 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

• Outline: — Smooth

• Radiodensity: Uniformly radiolucent.

• Effects: —Associated tooth unerupted and displaced

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.

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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 image. 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.

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