Pathology of the Head and Neck

Maxillofacial Skeleton and Teeth Chapter 4 109Gingival cysts of infants occur either singularly ormultiply on the edentulous alveolar ridge of the newborninfant. When occurring at the midline of the palate,they are known as palatal cysts of infants. These tinylesions, usually not larger than 3 mm, disappear spontaneouslywithin a short time. Histologically, they resembleepidermoid cysts [24, 94]. Historically, Epstein’spearls and Bohn’s nodules are terms that have been usedfor these lesions.4.3.3 Non-Odontogenic Cysts4.3.3.1 Nasopalatine Duct CystNasopalatine duct cysts arise within the nasopalatinecanal from epithelial remnants of the nasopalatine duct.Radiologically, they present as radiolucent lesions situatedbetween the roots of both maxillary central incisorteeth. The cyst lining may be pseudostratified columnarciliated epithelium, stratified squamous epithelium,columnar or cuboidal epithelium and combinations ofthese. As surgical treatment comprises emptying thenasopalatine canal, the specimen always includes theartery and nerve that run in this anatomic structure.These are seen within the fibrous cyst wall and formthe most convincing diagnostic feature, as the specificepithelial structures may be obscured by inflammatorychanges. Recurrences are rarely seen, and are probablydue to incomplete removal [168].4.3.3.2 Nasolabial CystNasolabial cysts are located in the soft tissue just lateralto the nose at the buccal aspect of the maxillary alveolarprocess and are thought to arise from the nasolacrimalduct. Non-ciliated pseudostratified columnar epitheliuminterspersed with mucous cells form the epitheliallining. These features may be lost through squamousmetaplasia [180]. Apocrine metaplasia of the cyst lininghas also been reported [83]. Treatment consists ofenucleation.4.3.3.3 Surgical Ciliated CystSurgical ciliated cysts arise from detached portionsof the mucosa that line the maxillary antrum and areburied within the maxillary bone. This may occur aftertrauma or surgical intervention in this area [93]. Mostly,the cyst is an incidental radiographic finding, observedas a well-defined unilocular radiolucency adjacent to themaxillary antrum.The cyst lining is similar to the normal mucosal surfaceof the paranasal cavities: pseudostratified ciliatedcolumnar epithelium with interspersed mucous cells.Treatment consists of simple enucleation.4.3.4 Pseudocysts4.3.4.1 Solitary Bone CystThe solitary bone cyst , also known as traumatic bone cystor simple bone cyst is confined to the mandibular body.Its pathogenesis is ill-understood; a remnant of intraosseoushaemorrhage is the most favoured hypothesis. Radiographsshow a cavity that varies from less than 1 cmin diameter to one that occupies the entire mandibularbody and ramus. At surgical exploration, one encountersa fluid-filled cavity. Material for histologic examinationmay be difficult to obtain as a soft tissue liningof the bony cavity may be entirely absent or very thin.If present, it usually consists only of loose fibrovasculartissue, although it may also contain granulation tissuewith signs of previous haemorrhage such as cholesterolclefts and macrophages loaded with iron pigment [136].Sometimes, this cyst develops simultaneously with a varietyof fibro-osseous cemental lesions [62].4.3.4.2 Focal Bone Marrow DefectThe focal bone marrow defect represents an asymptomaticradiolucent lesion of the jaws that containsnormal hematopoietic and fatty bone marrow. It is alsocalled osteoporotic bone marrow defect . This conditionis mostly seen at the angle of the mandible where it revealsits presence as a radiolucency with more or lesswell-defined borders. Due to the lack of radiographicspecificity, the lesion is usually biopsied. Then, histologicexamination will reveal the presence of normalhematopoietic marrow [141]. Of course, further treatmentis superfluous.4.4 Odontogenic TumoursOdontogenic tumours comprise a group of lesions thathave in common that they arise from the odontogenictissue. They develop from the epithelial part of the toothgerm, the ectomesenchymal part or from both. Theirbehaviour varies from frankly neoplastic, includingmetastatic potential, to non-neoplastic hamartomatous.Some of them may recapitulate normal tooth developmentincluding the formation of dental hard tissues suchas enamel, dentin and cementum [129]. Table 4.2 gives