Nonodontogenic cysts, cyst-like lesions, and myospherulosis

Clinical and radiographic findings

• This is most frequently encountered in the fourth and fifth decades of life with a slight male predilection, and it presents as a painless swelling of the anterior palate immediately posterior to the central incisors; teeth are vital but may have been endodontically treated on the assumption that the radiolucency represented periapical pathology.

• There is a well-demarcated, unilocular, round, ovoid, or heart-shaped radiolucency (because of the superimposed nasal spine seen in intraoral radiographs) between the maxillary central incisors, causing root divergence when large; while most cyst are in the midline and symmetric, some are not ( Fig. 16.1 ).

  

Etiopathogenesis and histologic features

The epithelium derives from remnants of the nasopalatine duct that runs within the incisive canal from the junction of the nasal septum and the floor of the posterior nasal cavity anteriorly on either side of the midline of the palate to exit in the incisive papilla just behind the maxillary central incisors.

• The cyst is lined by one of the following: nonkeratinized, stratified squamous epithelium (most common); pseudostratified, columnar, and ciliated epithelium with scattered mucous cells (30% of cases); low cuboidal epithelium; and often a combination of these. The basement membrane may be densely hyalinized ( Figs. 16.2 and 16.3 ).

  
  

• The nasopalatine neurovascular bundle is present in approximately half the cases and a cartilaginous rest or myxo-chondroid material may be present.

Differential diagnosis

• A cyst with the same histopathology removed in the same area but not within bone is the cyst of the incisive papilla (see Chapter 2 ).

• A cyst lined by nonkeratinized stratified squamous and respiratory epithelium in the anterior maxilla centered around endodontically teeth represents apical radicular (periapical) cyst often with mucous and ciliated cell prosoplasia.

Management and prognosis

• Curettage or enucleation is curative, and the recurrence rate is insignificant.

Clinical and radiographic findings

• This cyst occurs in the fourth decade of life, has a 4:1 male predilection, and presents as a painless swelling in the midline of the palate posterior to, and not in communication with, the nasopalatine foramen.

• It presents as a well-demarcated, round or ovoid, unilocular radiolucency in the midline of the hard palate ( Fig. 16.4 ).

  

Etiopathogenesis and histopathologic features

The lining putatively arises from entrapped epithelium during fusion of the lateral palatal shelves. Some suggest that a cyst in this location could represent a nasopalatine duct cyst that developed from remnants of the nasopalatine duct in the palate posterior to the incisive foramen.

• The cyst is lined by ciliated, pseudostratified columnar or uniformly thin, nonkeratinized, stratified squamous epithelium.

Differential diagnosis

• Posterior extension of the nasopalatine duct cyst should be considered if it communicates with the nasopalatine foramen.

• If it is parakeratinized and fulfills the histopathologic criteria for a keratocystic odontogenic tumor (odontogenic keratocyst), then it is likely a posterior extension of a primordial cyst of a mesiodens. If orthokeratin is present, it would represent an orthokeratinized odontogenic cyst.

Management and prognosis

• Enucleation or curettage is curative.