This article focuses on describing nonodontogenic cysts of the oral and maxillofacial region. The lesions described include nasopalatine duct canal cyst, nasolabial cyst, traumatic bone cyst, Stafne bone cyst, aneurysmal bone cyst, focal osteoporotic bone marrow defect, dermoid cyst, epidermoid cyst, pilar cyst, and sebaceous cyst. The intent of this article is to make general dentists aware and knowledgeable of the nonodontogenic cysts they may encounter in everyday practice, so they can adequately manage or make an appropriate referral to improve treatment outcomes and reduce patient morbidity.
Key points
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Nonodontogenic cysts of the jaws are not a common occurrence and occur much less frequently than odontogenic cysts of the jaws.
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Nonodontogenic cysts of the jaws most commonly encountered are the nasopalatine duct canal cyst, nasolabial cyst, traumatic bone cyst, Stafne bone cyst, aneurysmal bone cyst, and focal osteoporotic bone marrow defect.
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Nonodontogenic cysts of the oral and maxillofacial complex (excluding the jaws) commonly seen are the dermoid cyst, epidermoid cyst, pilar cyst, and sebaceous cyst.
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It is important that general dentists are able to recognize these nonodontogenic cysts of the oral and maxillofacial complex to adequately manage or make an appropriate referral to reduce patient morbidity.
Introduction
A cyst is a pathologic cavity lined by epithelium and filled with fluid or semifluid content and may either locate in soft tissue or within the jaw bone, originating in odontogenic or nonodontogenic tissues. Jaw bones show predilection for odontogenic cysts, whereas nonodontogenic cysts are uncommon. Both odontogenic and nonodontogenic cysts produce radiolucent defects causing destruction of osseous structure. Hence it is essential to understand clinical behavior and management strategies, and failure to treat at the right time may increase patient morbidity. This article focuses on the clinical presentation, investigation findings, and treatment options of nonodontogenic cysts of the jaw. The conditions discussed in this article are listed in Box 1 .
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Nasopalatine duct canal cyst
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Nasolabial cyst
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Traumatic bone cyst
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Stafne cyst
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Aneurysmal bone cyst
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Focal osteoporotic bone marrow defect
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Epidermoid cyst
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Dermoid cyst
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Pilar cyst
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Sebaceous cyst
Nasopalatine Duct Canal Cyst
Nasopalatine duct canal cyst is also known as an incisive canal cyst or median palatine cyst when it is located more posterior in the palate ( Fig. 1 ). These cysts are typically located in the nasopalatine canal or in the palatal soft tissues where the canal opens. This cyst is the most common nonodontogenic cyst in the oral cavity. Prevalence of this cyst is 2.2% to 11.6% of the population, or 1 out of every 100 individuals. A nasopalatine duct canal cyst forms from the proliferation of the right and left palatine processes to the premaxilla. Anatomically, the exit of the canal is slightly posterior to the incisive papilla. Typically, the nasopalatine duct degenerates in humans; however, the epithelial remnants remain and have the potential for cystic enlargement. The most likely cause of the nasopalatine duct canal cyst is persistence of the epithelial remnants following duct degeneration. The exact stimulus to cystic formation at this time is unknown.
Patient history
Nasopalatine duct canal cyst has a male predilection of 3:1. Median palatine cyst has a male predilection of 4:1. They are most common in the fourth to sixth decades, although they can be seen at any age. Median age is 42.5 years. Usually they are identified as an asymptomatic palatal midline swelling by the patient or the dentist on clinical examination. The patient may complain of symptoms if the cyst is secondarily inflamed or infected.
Intraoral examination
Cysts present as symmetric swelling in the anterior region of the midline palate or as midline radiolucency on radiographs ( Fig. 2 ). They are usually asymptomatic, with midline swelling that is suspicious for a lesion on clinical examination. Symptoms can arise from secondary infection. Sinus formation and drainage at the palatine papilla may be seen if infected. The rates of symptomatic lesions are variable in the literature and do not follow any predictable patterns, such as age or size.
Imaging and additional testing
Radiographically, the lesion is a well-circumscribed, round, ovoid, or heart-shaped radiolucency near the maxillary incisors ( Figs. 3 and 4 ).The nasopalatine duct cysts range in size from several millimeters to centimeters; the average size is 1.5 cm. Lamina dura of adjacent teeth is intact, but lesions can cause divergence of the roots of the maxillary incisor teeth and less commonly are known to cause external root resorption. The lesion can appear heart-shaped because of the superimposition of the anterior nasal spine. Histopathologically, the epithelial lining of this cyst ranges from stratified squamous to pseudostratified columnar in areas close to the nasal cavity. The connective tissue contains a nasopalatine neurovascular bundle composed of arteries and nerves ( Fig. 5 ).
Treatment
Treatment via surgical enucleation is curative without recurrence. Marsupialization of larger lesions before enucleation can be considered. The recurrence rate of this lesion is low.
Nasolabial Cyst
Nasolabial cysts are soft tissue cysts of the upper lip. These cysts are very rare, comprising 0.7% of all jaw cysts. The cyst is found in the upper lip, lateral to the midline or in the region of the lateral and canine teeth. The pathogenesis of the cyst is unclear; although a few theories do exist. One theory suggests that this cyst arises from nasolacrimal duct ectopic epithelium. Another theory suggests that this cyst arises from epithelial remnants at the fusion line of the medial and lateral nasal processes during embryogenesis.
Intraoral examination
This lesion presents as upper lip swelling, elevated ala of the nose, obliteration of the vestibule, and elevation of the mucosa of the nasal vestibule ( Fig. 6 ). Patients commonly complain of facial deformity. Nasolabial cysts are bilateral in 10% of cases ( Fig. 7 ).
Imaging and additional testing
Because nasolabial cysts are soft tissue lesions, they are not seen on traditional plain film radiographs. Cone beam computed tomography (CT), traditional CT, and MRI show a well-circumscribed soft tissue mass of varying size ( Fig. 8 ). Histopathologically, the epithelial lining of the cyst is pseudostratified columnar epithelium with abundant goblet cells. Some cysts have stratified squamous epithelium as well as cuboidal epithelium ( Fig. 9 ).
Treatment
The traditional approach to treatment is surgical excision via an intraoral or sublabial approach. Because of proximity to nasal mucosa and floor, nasal mucosa may need to be excised in order to completely remove the cyst. This treatment can lead to an oronasal fistula, which requires surgical repair. Endoscopic marsupialization via a transnasal approach is another treatment modality.
Pseudocysts
Traumatic Bone Cyst
This lesion is also known as a simple bone cyst, hemorrhagic cyst, intraosseous hematoma, idiopathic bone cyst, extravasation bone cyst, solitary bone cyst, or solitary bone cavity. The term cyst is a misnomer because this lesion lacks an epithelial lining. The pathogenesis of traumatic bone cyst formation is not known. Some cases can be attributed to prior trauma, which results in hematoma formation within the intramedullary region of bone. Rather than going through the organization process, the clot breaks down, leaving an empty cavity. Other causes include cystic degeneration of primary tumors of bone, such as central giant cell granuloma; ischemic necrosis of bone; and calcium metabolism disorders.
Patient history
Teenagers are most commonly affected, but traumatic bone cysts have been reported in many age ranges. There is an equal gender predilection, and it can be associated with swelling. Patients are usually asymptomatic. It can be seen in association with florid osseous dysplasia.
Intraoral examination
Traumatic bone cyst usually presents as an asymptomatic lesion. Traumatic bone cavity is an empty dead space in medullary bone. It is most frequently reported in the mandible, with a predilection for the anterior region. There are a few reports of bilateral cases. Surrounding teeth are usually vital.
Imaging and additional testing
Traumatic bone cyst is most often found as an incidental finding on dental radiographs. On dental radiographs, the lesion is a well-circumscribed irregularly shaped area of radiolucency with poorly defined borders ( Fig. 10 ). Inter-radicular scalloping and mild root resorption may be seen. Histopathologically, minimal amounts of fibrous tissue from the bony wall may be seen ( Fig. 11 ). Lesions can be empty or include blood or sanguinous fluid. This cyst lacks epithelial lining, and hence is called a pseudocyst. Giant cells adjacent to the bone surface are seen in some cases.
Treatment
The lesion is managed by a surgical procedure, and surgical entry into the lesion initiates bleeding to assist in normal healing. Blood clot formation results in bony repair without recurrence.
Stafne Bone Cyst
Stafne cyst is a pseudocyst. It is also known as a static bone cyst. It is a developmental defect that is an anatomic indentation of the posterior lingual cortex of the mandible into the medullary space and resembles a cyst on radiographs. This bone pseudocyst usually contains submandibular salivary gland tissue or fat. The cause of the lesion is unknown. Some investigators suggest that the lesion is caused by entrapment of salivary gland or other soft tissue during mandible development. Other possible explanations include lingual mandibular cortical erosion from hyperplastic salivary gland tissue.
Patient history and intraoral examination
Almost all cases involve adults, most often men. The lesion is always asymptomatic and is often discovered as an incidental finding on dental panoramic radiographs. The patients are usually asymptomatic, and no specific clinical changes are observed.
Imaging and additional testing
On a dental panoramic radiograph, it appears as a well-circumscribed oval radiolucency located between the inferior alveolar canal and inferior border of the posterior mandible ( Fig. 12 ). Occasionally it is bilateral and, rarely, anterior to the mandibular first molar. CT and MRI show tissue with the same appearance as fat in the defect, or salivary gland tissue from adjacent salivary gland into defect ( Fig. 13 ).
