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.

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

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

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.

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

• Age: Usually adults, 20–50 year-olds.

• Frequency: Most common of all jaw cysts (about 70%).

• Site: Apex of any non-vital tooth, particularly upper lateral incisors.

• Size: 1.5–3 cm in diameter (if smaller the radiographic distinction between cyst and granuloma cannot usually be made).

• Shape: — Round

— Unilocular.

• Outline: — Smooth

— Well defined

— 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.