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Non-odontogenic cysts

Nasopalatine duct or incisive canal cyst

The formation of a cyst in the incisive canal is surprisingly common in some studies, accounting for around 5% of jaw cysts and making this the commonest non-odontogenic cyst of the jaws. They are also known as incisive canal cysts. 

Clinical features

These cysts arise in the incisive canal, and the presentation depends on where in the canal they form. They may form a superficial soft tissue cyst in the incisive papilla if at the oral end  grow primarily into the nose if at the superior end or grow slowly in the bone of the anterior palate if they arise in the middle. Often they burst into the mouth or nose, producing intermittent salty discharge. Cysts from the middle of the canal expand the bone of the palate downward and upward, while they grow forward, over or between the central incisor apices to expand the anterior alveolus in the midline.

Nasopalatine cyst. Typical presentation with a dome-shaped bluish enlargement overlying the incisive canal.

Radiography features

 A rounded radiolucent area with a corticated outline at the site of the incisive canal. In anterior occlusal or periapical films they may appear heart-shaped because of superimposition of the anterior nasal spine.

They are usually symmetrical but become asymmetrical when large.

 The root apices of the central incisors are often pushed apart.

 Nasopalatine cyst. The usual appearance is a rounded or pear-shaped area of radiolucency, at the site of the incisive canal.

 

Nasopalatine duct cyst: key features

  • Often asymptomatic, chance radiographic findings
  • Form in the incisive canal region
  • Arise from vestiges of the nasopalatine duct
  • Lined by squamous or columnar respiratory epithelium
  • The long sphenopalatine nerve and vessels may be present in the wall
  • Can usually be recognised radiographically
  • Do not recur after enucleation

Aneurysmal bone cyst

Aneurysmal bone cysts are pseudocysts because they appear radiographically as cyst-like lesions but microscopically exhibit no epithelial lining.

 This lesion represents a benign lesion of bone that may arise in the mandible, the maxilla, or other bones.

Within the craniofacial complex, approximately 40% of lesions are located in the mandible and 25% are located in the maxilla.

Aneurysmal Bone Cyst

Etiology:  An aneurysmal bone cyst (ABC), usually considered as a reactive lesion of bone rather than a cyst or true neoplasm, is believed to represent an exaggerated, localized, proliferative response of vascular tissue in bone.

 The etiology of ABCs remains unclear, and they are occasionally seen to develop in association with other primary lesions such as fibrous dysplasia, central hemangioma, giant cell granuloma, and osteosarcoma

Clinical & radiographic  features

Teenagers and young adults affected

An ABC in the jaw usually manifests as an occasionally painful and a fairly rapidly enlarging bony swelling (usually buccal or labial). The involved area may be tender on palpation.

 Mandible is affected more often than maxilla (3:1).  with slight female predilection.

ABCs rarely occur in jaws, with an incidence rate of 2% reported so far.

Most of the cases have had a unilocular occurrence.  Bilateral occurrence in the mandible  is rare.

Multilocular lucency,

 Bilateral occurrence in the mandible

Mandibular aneurysmal bone cyst in an elderly patient

Radiographic features include the presence of a destructive or osteolytic process with slightly irregular margins.

 When the alveolar segment of the mandible and the maxilla is involved, teeth may be displaced with or without concomitant external root resorption.

Differential diagnosis

central giant cell granuloma, hyperparathyroidism, cherubism.

Treatment

Excision: no bleeding hazard

Traumatic (simple) bone cyst

A traumatic bone cyst is an empty intrabony cavity that lacks an epithelial lining. The designation of pseudocyst relates to the cystic radiographic appearance and gross surgical presentation of this lesion. It is seen most often in the mandible.

Etiology

Unknown; trauma sometimes suggested

May be related to bleeding in the jaw with clot resorption

Clinical features

Lucency discovered on routine examination

Empty “dead” space in medullary bone, especially mandible

Teenagers most commonly affected

Simple bone cyst

Radiographically

A well-delineated area of radiolucency with an irregular but defined edge is noted. Inter-radicular scalloping of varying degrees is characteristic, and occasionally slight root resorption may be observed.

Traumatic bone cysts have often been seen in association with florid osseous dysplasia. The relationship between these two entities is not understood.

Treatment

Surgical entry to initiate bleeding and stimulate healing

Some may heal spontaneously

Stafne bone cavity (SBC), is an asymptomatic bone depression which is referred to as pseudocyst without epithelial lining. 

Commonly they occur in the mandibular molar region, related to the submandibular gland below the mandibular canal.

Rarely, they appear in the apical region of the premolars and canines of the anterior mandible, associated with the sublingual glands above the mylohyoid muscle.

 Etiology of SBC is unknown, but the surrounding tissue or facial artery mechanical pressures can be the origin of this developmental anomaly.

Radiographic Features:

They are unilocular, round or ovoid radiolucent cyst like defects with well-defined, thick and corticated border and their diameter size varies 1-3 cm.  They may  be sometimes  seen as  multilocular with irregular borders.  If SBC have well-defined, thick and corticated borders and oval shape under the mandibular canal in contact with the base of the mandible, differential diagnosis can be easy.

 However, if they are noticed higher or above the mandibular canal and have no connection with the mandibular base with irregular borders, they can cause misdiagnose.

Computed tomography (CT) or magnetic resonance imaging (MRI) should be useful for differential diagnosis.

The radiolucent area, which was located at the posterior right molar region of the mandible below the inferior dental canal on panoramic radiography

 (a) The cross-sectional images presented the invagination of the lingual cortex up to the buccal cortex. (b) The axial images of the cone beam computed tomography scan showed a mandibular lingual wall defect at the molar region with vestibular extension

Three-dimensional cone beam computed tomography volume rendering reconstructed images of the patient showed lingual bone defect field

 Oval shaped, well-bordered cystic lesion (white arrow) between the second molar and the mandibular angle, slightly above the inferior mandibular line in panoramic radiograph.

Key features

Diagnostic on panoramic film

 No symptoms

 No biopsy or treatment—radiographic diagnosis

Differential diagnosis

 The  mandibular depressions includes several pathologic entities, such as, odontogenic cyst, simple bone cyst, ameloblastoma, hemangioma, myxoma, central giant cell lesion, fibro-osseous lesions, multiple myeloma, eosinophilic granuloma, benign salivary gland tumors, neurogenic tumors, and metastatic disease.

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