9: Cysts

9 Cysts

J. Marley, C.G. Cowan

• A variety of cysts occur in the orofacial region and often present first to the general dental practitioner.
• Cysts are usually classified as odontogenic or non-odontogenic in origin and may present within the hard and soft tissues of the head and neck region.
• Other lesions; benign and malignant, can present with similar clinical and radiological findings (see Ch. 8). Histology is required to establish the diagnosis.
• There are two methods of treatment: enucleation, a one-stage procedure to remove the entire cyst, and marsupialization, a method of decompressing the cyst by converting it into a pouch.
• Small cysts are best treated with primary enucleation.
• Marsupialization is often the most appropriate treatment for extensive lesions, particularly for the elderly and/or patients with significant co-morbidity or if the cyst is infected or in close proximity to important anatomical structures.

ASSUMED KNOWLEDGE

It is assumed that at this stage you will have knowledge/competencies in the following areas:

• anatomy of the face and jaws
• WHO classification of odontogenic tumours and cysts
• pathological and radiological appearance of cysts and other benign oral lesions
• practice of surgical endodontics (apicectomy) (see Ch. 6).

If you feel you are not competent in these areas, revise them before reading this chapter or cross-check with relevant texts as you read.

INTENDED LEARNING OUTCOMES

At the end of this chapter you should be able to:

1. Recognize cysts according to clinical symptoms and signs, anatomical site and radiographic appearance
2. Develop a differential diagnosis based on the clinical features, anatomical site and radiographic findings
3. Understand the principles of surgical management relating to both enucleation and marsupialization
4. Propose treatment options according to probable diagnosis, anatomical relationships and size of lesion
5. Understand the level of operator experience required for surgery and recognize cases that will require referral
6. Either alone or in conjunction with a specialist, advise patients concerning the nature and effects of their disease, its treatment and any follow-up regimen.

OVERVIEW

Cysts of the face and jaws are common and present a wide variation in type. The vast majority of cysts are intrabony and odontogenic in origin and these will form the basis of this chapter with minor reference to the rarer soft-tissue cysts, e.g. dermoid and branchial cysts.

By definition true cysts are developmental or reactive lesions with the vast majority growing by fluid accumulation. This gives them their benign characteristics with the typical resorption of bone and displacement of adjacent structures such as the neurovascular bundle as a result of the pressure effect, properties that are common to benign tumours as well. There are, however, some cysts that grow by cell proliferation, e.g. the odontogenic keratocyst, and they tend to behave in a more aggressive manner with recurrence common. This cyst has been re-classified as a locally invasive tumour (Philipsen 2005), although it should be noted that unlike most tumours, this condition can be successfully treated by partial removal (see below concerning marsupialization). In addition there are tumours, locally invasive and true malignancies, that can appear cystic on presentation, e.g. ameloblastoma, adenoid cystic carcinoma and some sarcomas. Malignant change in cysts has been reported but is a very rare occurrence.

Despite these variations, presenting symptoms and signs tend to be similar. The principles of management are dictated by predicted behaviour, which in turn is dependent on histological type.

This chapter will be confined to clinical diagnosis and principles of treatment of the commonly occurring cysts of the mouth and jaws.

DEFINITION

A cyst is a pathological cavity usually lined by epithelium with fluid or semifluid contents, not created by the accumulation of pus.

DIAGNOSIS

Presenting symptoms and signs

Intrabony cysts may remain symptomless for many years and only come to light as an incidental finding on routine dental inspection or radiographic investigation (Fig. 9.1) or can present in a variety of ways described below.

image

Fig. 9.1 Occlusal radiograph of a radicular (dental) cyst, displaying a well-defined radiolucency arising from a non-vital upper lateral incisor.

Association with teeth

Radicular (dental) cysts are the most common of all cysts and are associated with a non-vital root of a tooth. Ectopic teeth can often be associated with cysts either as the primary cause as with the dentigerous cyst (Fig. 9.2) or when displaced by a cyst, such as an odontogenic keratocyst. It is important to appreciate that other more significant conditions, e.g. ameloblastoma, may also present in this manner (see Ch. 8).

image

Fig. 9.2 A dentigerous cyst associated with an unerupted lower third molar.

Site

Many cysts show a predilection for specific areas. For example, 75% of odontogenic keratocysts present at the mandibular angle (Fig. 9.3) whilst 88% of glandular odontogenic cysts occur at the anterior mandible (Cawson et al. 2001). Some cysts are completely site-specific such as the nasopalatine duct cyst, which arises from tissues within the incisive canal, and the paradental cyst, which is associated with impacted lower third molars. Also of note is the group of cysts that present in the gingival area including the inflammatory lateral periodontal cyst (a variant of a radicular cyst), the true lateral periodontal cyst, the peripheral odontogenic keratocyst and gingival cyst of adults. These classically present coronal to the apices and in-between teeth in the premolar areas.

image

Fig. 9.3 An odontogenic keratocyst at the angle of the mandible.

Site is also a major diagnostic feature for the rare soft-tissue cysts, particularly the developmental dermoid, nasolabial and thyroglossal duct cysts (see below).

Swelling

Swelling is a common presenting complaint and if extensive can cause both intraoral and extraoral asymmetry. Importantly the swelling is normally clinically discrete and well demarcated. Where there has been extensive expansion of the cyst the overlying bone will be thin or absent. In the former, the surface will feel firm but flexible, but if the overlying bone has been completely eroded it will appear as a tense bluish swelling that feels ‘fluctuant’ (Fig. 9.4) (see Ch. 7 for a description of fluctuance).

image

Fig. 9.4 Bluish swelling associated with an eruption cyst on a lower first molar.

Patterns of growth and anatomical site

How the cyst grows and the anatomical site will dictate the extent and presentation of swelling. Cysts will expand quicker through cancellous and thin cortical bone and so tend to present sooner in the anterior region than in the posterior mandible. In contrast, the late presentation of cysts in the posterior mandible/maxilla reflects cysts spreading along cancellous bone or into the maxillary air sinus respectively, thus making clinically obvious swelling a late feature. This can be of major significance in terms of making the initial diagnosis, primary management and follow-up, particularly for keratocysts where recurrence is common.

Cysts that develop by fluid accumulation and consequent hydrostatic pressure, e.g. inflammatory and dentigerous cysts, will develop spherically and so expand through cortical bone relatively early. In contrast, odontogenic keratocysts grow by cellular proliferation. Expansion tends be to a late feature, with the keratocyst preferentially expanding within the cancellous bone, leading to a greater anteroposterior dimension on radiographic examination.

Pain

Pain is uncommon and is usually indicative of acute infection. This can arise in any of the cyst types but is more likely in radicular cysts, which have an inflammatory aetiology. On rare occasions large mandibular cysts that become infected cause dysaesthesia in the inferior alveolar nerve distribution or acute sinusitis in the case of an infected maxillary cyst.

Lobulation

Where a radiolucency displays lobulation it is strongly suggestive of the keratocyst (Fig. 9.3), which has a pattern of cyst growth with ‘invasion’ of lining epithelium through the cancellous bone space leaving behind isthmi of bone.

Associated signs/symptoms

As well as eroding bone, cysts can affect the adjacent structures, teeth and neurovascular structures. Erupted teeth are occasionally loosened or displaced, sometimes enough to disrupt the occlusion or alter the shape of the alveolus and the fit of a prosthesis. Rarely cysts can resorb teeth (infection increasing the risk). In extreme cases mandibular cysts can cause so much destruction of bone that a pathological fracture occurs (Fig. 9.5).

image

Fig. 9.5 An extensive cyst with a fracture of the mandible.

Clinical features of jaw cysts

• Often none at all (chance finding on X-ray)
• Swelling (usually bony, smooth but later soft, bluish and fluctuant)
• Displacement of teeth
• Increased mobility of teeth
• Evidence of a cause (missing or non-vital teeth, infection)
• Rarely pathological fracture

Special investigations

Radiology is a key investigation in determining the diagnosis and the extent and anatomical relationships of the lesion. It is therefore important in treatment planning and issues relating to consent. Simple plain films such as orthopantomogram (OPT), periapical and occlusal views are normally sufficient but for extensive cysts, particularly if they may be extending into soft tissue (e.g. the lingual area or the maxillary sinus and pterygoid regions), advanced imaging such as CT will be required. For further details of the radiological features of cysts, readers are referred to standard texts on dental and maxillofacial radiology. However, the general radiological features of cysts can be summarized as radiolucencies with a well-defined, corticated margin. The features of site, shape, relationship to teeth and whether there is any lobulation will all contribute to the diagnosis.

The rare soft-tissue cysts—branchial, thyroglossal and dermoid—need specialist investigation, which may include ultrasound, CT and MRI scanning.

Given the variety of cysts with their differing propensity to recur and the possibility of other cyst-mimicking pathology, a definite diagnosis is essential.

All cyst specimens should therefore be submitted for histological examination (see Ch. 8). Often this takes the form of an excisional biopsy when establishment of the histological diagnosis is coupled with complete removal of the lesion. For larger lesions it is essential to match the cyst type to the appropriate surgical treatment so it is sometimes best to perform an incisional biopsy to establish diagnosis before considering major surgery.

The diagnosis of cysts in the upper premolar and molar regions can be problematic given the relation of the maxillary antrum. On occasions aspiration biopsy can be of value in confirming presence of a cyst. This involves a small incision through the mucosa to expose the appropriate area and depending on the thickness of bone, either direct introduction of a wide-bore needle or use of a bone drill can facilitate this. Aspiration of air indicates the maxillary sinus. Fluid aspiration indicates a cyst, with mucus being suggestive of an antral mucosal cyst, straw-coloured fluid with cholesterol crystals a dental cyst and pus an infected cyst or sinus infection. No aspirate may mean the cyst contents are too viscous to be aspirated but significantly it may indicate a solid lesion and therefore a possible neoplasm.

Radiological features

• Well-defined radiolucency with a corticated margin
• Possibly unilocular/>

Related posts:

  1. 3: Control of pain and anxiety: selection of and preparation for sedation or anaesthesia
  2. 17: Surgery of the temporomandibular joint
  3. 10: Malignant disease of the oral cavity
  4. 13: Maxillofacial trauma
  5. 4: Extraction of teeth
  6. 11: Surgical aids to prosthodontics, including osseointegrated implants

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Jan 14, 2015 | Posted by in Oral and Maxillofacial Surgery | Comments Off on 9: Cysts

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