Shear's Cysts of the Oral and Maxillofacial Regions - Paul M. Speight

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1.1–1.3).

      1 Radicular cystResidual cyst

      2 Inflammatory collateral cystsParadental cystMandibular buccal bifurcation cyst

      1 Dentigerous cystEruption cyst

      2 Odontogenic keratocyst

      3 Lateral periodontal cystBotryoid odontogenic cyst

      4 Gingival cyst of adults

      5 Gingival cyst of infants

      6 Glandular odontogenic cyst

      7 Calcifying odontogenic cyst

      8 Orthokeratinised odontogenic cyst

      Non‐odontogenic cysts of the jaws are mostly developmental in origin and arise from vestigial epithelial remnants of ductal structures or from inclusions at the line of fusion of the palatal shelves. The nasolabial and mid‐palatal raphe cyst actually occur in the soft tissues, but are so closely apposed to the maxillary bone that they are included in the classification of jaw cysts. The surgical ciliated cyst is included here because it arises within the alveolar bone of the maxilla. Pseudocysts are not epithelial lined, but are included because they are important in the radiological differential diagnosis of cystic jaw lesions. As discussed above, we are content to use ‘cyst’ as a diagnostic term for the simple bone cyst, since this is clearly understood and widely used by clinicians who recognise that they present clinically and radiologically as a cystic lesion. Stafne bone cavity is neither a cyst nor a pseudocyst, but is an anatomical anomaly causing an indentation of the mandible that appears as a cystic lesion on radiology or imaging. It is often included in classifications and we include it here because of its importance in the radiological differential diagnosis of cystic lesions. Osteoporotic bone marrow defects are controversial lesions, but they present as cystic radiolucencies and must also be considered in the differential diagnosis.

      1 Nasopalatine duct cyst

      2 Nasolabial cyst

      3 Mid‐palatal raphe cyst of infants (Epstein pearls)

      4 Surgical ciliated cyst

      1 Simple bone cyst

      2 Stafne bone cavity

      3 Osteoporotic bone marrow defects

      Cysts affecting the salivary and minor mucous glands of the head and neck are common and may be developmental or reactive in nature. Retention and extravasation cysts (mucoceles) are the most common and may arise at any site associated with minor glands that are found throughout the submucosa of the upper aerodigestive tract and paranasal sinuses. Here we include cystic lesions of the major salivary glands as well as cysts associated with minor glands of the oral cavity and maxillary sinus. Ranula is included as a separate lesion because it has distinctive and specific clinical features and problems of management. Cystic neoplasms are not included. Intraoral lymphoepithelial cysts are included in this category even though their origin is uncertain. Some arise from intraoral tonsillar tissue, while others appear to be associated with dilated ducts of minor salivary gland.

      1 MucocelesMucous extravasation cystMucous retention cystRanula

      2 Salivary duct cyst (of the major glands)

      3 Intraoral lymphoepithelial cyst

      4 Lymphoepithelial cysts of the parotid gland

      5 Polycystic disease of the parotid gland

      1 Mucoceles

      2 Retention cyst

      3 Pseudocysts

      1 Dermoid and epidermoid cysts

      2 Cysts of foregut originHeterotopic gastrointestinal cystBronchogenic cyst

      3 Branchial cleft cysts

      4 Thyroglossal duct cyst

      5 Nasopharyngeal cyst

      6 Thymic cyst

      Frequency statistics differ from incidence studies in that they are not standardised against known population data, such as age, sex, and ethnicity. For data to be comparable between populations and internationally, age‐standardised incidence rates per 100 000 are compared with a standard world population. Incidence data are a requirement for all national cancer registries, but most benign lesions, including cysts, are not registered and thus incidence data is not available for the odontogenic cysts. Epidemiological data are therefore presented as the relative frequency of each cyst type as a proportion of the total number of cysts encountered within a population, or of the total number of specimens received. This gives clinicians an estimate of the likelihood of encountering these lesions in everyday practice.

      Frequency studies are rarely based on the general population, but are usually derived from archival records of diagnoses made in a hospital department, usually pathology departments. While these provide useful data on the behaviour and treatment of different diseases, they are of limited use in international comparative studies. Table 1.3 shows the wide variation in the frequency of the three most common odontogenic cysts in different parts of the world. Almost without exception, these data are derived from retrospective analyses of pathology records and the frequency of each cyst type may depend on local protocols for patient referral and management, or even on individual pathologists' criteria for diagnosis. For example, a high frequency of radicular cysts may reflect a high caries rate in the local population, or a high rate of referral of periapical lesions. Conversely, a low frequency of radicular cysts may arise if the local practice is not to submit periapical lesions for histological analysis. In Chapter 4 we discuss the very low frequency of paradental cysts in some countries, where the lesion does not seem to be recognised as an entity and is therefore not diagnosed.

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