Overview and definition
The lateral periodontal cyst (LPC) is a rare, benign, developmental odontogenic cyst that arises within the alveolar bone adjacent or lateral to the root of a vital erupted tooth.[1][2] It is classified as a non-keratinized, non-inflammatory cyst and is considered the intraosseous counterpart of the gingival cyst of the adult.[2] The prevailing hypothesis attributes its origin to rests of the dental lamina, although some authors have favored reduced enamel epithelium as the source; the exact histogenesis remains debated.[2][3] LPC characteristically presents as a small, well-defined, unilocular radiolucency in the mandibular canine–premolar region and is managed by conservative surgical enucleation with a low recurrence rate.[1][2]
Terminology and classification
- Lateral periodontal cyst (LPC) is the accepted term in the current WHO Classification of Head and Neck Tumours, where it is listed among developmental odontogenic cysts.[2]
- The botryoid odontogenic cyst (BOC) is recognized as a multilocular (multicystic) variant of LPC with distinct clinical behavior.[2]
- The gingival cyst of the adult (GCA) is the extraosseous (soft-tissue) counterpart sharing histological features with LPC.[2]
- The term "lateral periodontal cyst" should not be applied to inflammatory cysts that happen to occupy a lateral periodontal position (e.g., lateral radicular cyst); the diagnosis requires exclusion of a pulpal etiology and confirmation of the characteristic non-inflammatory, non-keratinized histology.[2][4]
Epidemiology
- Frequency: LPC is rare, accounting for less than 1% of all jaw cysts.[3]
- Age: Peak prevalence in the fifth decade, with a broad range from the second to ninth decades.[2][3]
- Sex: Approximately equal sex distribution or a slight male preponderance.[2][3]
- Jaw distribution: The mandible is affected in the majority of cases, with the canine–premolar region being the most common site. The anterior maxilla is the next most frequent location. Posterior jaw involvement is uncommon.[1][2][3]
- Mean lesion size: Approximately 1.0 cm (range 0.2–3.0 cm), larger on average than the gingival cyst of the adult.[2]
Clinical presentation
LPC is characteristically asymptomatic and discovered incidentally on routine radiographic examination.[1][2] When clinical signs are present, they may include:
- A small, painless, firm swelling of the attached gingiva or alveolar mucosa, occasionally with a bluish hue[5][6]
- Loss of the interproximal buccal bone plate, detectable as localized soft-tissue fullness[5]
Tooth vitality
Adjacent teeth are vital unless previously endodontically treated; this is a key clinical feature distinguishing LPC from inflammatory periapical pathology.[1][2]
Tempo and complications
Growth is slow and progressive.[1] Cortical expansion is uncommon, and cortical perforation is rare.[1][2] Root resorption and tooth displacement are not statistically significant features of LPC compared with its botryoid variant.[2] Rare reported associations include ameloblastoma and squamous cell carcinoma arising within or adjacent to an LPC.[1]
Radiographic findings
Location and distribution
The characteristic location is the interradicular alveolar bone between the roots of adjacent erupted teeth, or along the lateral surface of a tooth root between the alveolar crest and the root apex.[1][2] The mandibular canine–premolar region is the most common site; the anterior maxilla is the second most frequent.[2] Occasional cases arise in a periapical position, mimicking endodontic pathology.[7]
Periphery and shape
LPC presents as a well-defined, corticated radiolucency with a thin sclerotic border.[1][7] The shape is characteristically round, oval, or teardrop-shaped.[1] The well-circumscribed sclerotic margin is a consistent feature that aids recognition on both periapical and panoramic radiographs.[5][7]
Internal architecture
The internal structure is uniformly radiolucent (unilocular) without internal septation, calcification, or mixed density.[1][2] A multilocular radiographic appearance should raise suspicion for the botryoid odontogenic cyst variant, which demonstrates multiple cystic compartments histologically.[2]
Size
Most lesions measure less than 1 cm in diameter.[1] The mean size across large pooled data is approximately 1.0 cm, with an upper range of about 3.0 cm.[2]
Effects on teeth and adjacent structures
- Root resorption: Uncommon; adjacent roots typically maintain normal morphology.[1][2]
- Root divergence: Larger lesions may cause mild displacement or divergence of adjacent roots.[1]
- Lamina dura: Loss of the lamina dura of the adjacent tooth socket in contact with the lesion may be observed.[5]
- Periodontal ligament space: Secondary widening of the periodontal ligament space on the root surface abutting the cyst can be identified, particularly on cross-sectional imaging.[1]
Cortical involvement and extent
Expansion or perforation of the buccal or lingual cortical plates is rare.[1][2] The lesion is typically confined to the alveolar process without extension into the body or ramus of the mandible. Cross-sectional imaging can confirm cortical integrity and precisely localize the cyst relative to the buccal and lingual plates, which is useful for surgical planning.[1]
Variants
- Botryoid odontogenic cyst: The multicystic variant may present as a multilocular radiolucency, tends to be larger (mean ~2.8 cm), favors the mandible more strongly, occurs in older patients (sixth–seventh decades), and carries a substantially higher recurrence rate. Importantly, a multilocular histological pattern does not always produce a multilocular radiographic appearance.[2]
- Periapical presentation: Occasional LPCs arise at the apex rather than the lateral root surface, appearing as a well-corticated periapical radiolucency indistinguishable from a radicular cyst on imaging alone; vitality testing is essential.[7]
Differential diagnosis
The differential for a small, well-defined, unilocular radiolucency lateral to a vital tooth root in the canine–premolar region is narrow but includes entities with markedly different management requirements.
| Entity | Why it is considered | Best discriminator |
|---|---|---|
| Odontogenic keratocyst | Well-defined radiolucency in the premolar–anterior region with possible gingival swelling | OKC is frequently misdiagnosed as LPC in this location; OKC tends to be larger, may show scalloped margins, and has a much higher recurrence rate—biopsy is essential[4][8] |
| Radicular (periapical) cyst | Periapical or lateral radiolucency associated with a carious or restored tooth | Adjacent tooth is non-vital in radicular cyst; pulp vitality testing reliably separates the two entities[1][9] |
| Botryoid odontogenic cyst | Multilocular or large unilocular radiolucency in the same region, older patient | Multilocular radiographic pattern, larger size, and multicystic histology distinguish BOC; higher recurrence rate mandates more aggressive follow-up[2] |
| Glandular odontogenic cyst | Multilocular or unilocular radiolucency, anterior mandible, may cross the midline | Larger size, tendency to cross the midline, and complex epithelial lining with mucous cells and microcysts on histology differentiate from LPC[10][11] |
The highest-risk diagnostic pitfall is the clinical and radiographic mimicry between LPC and odontogenic keratocyst in the premolar–anterior region: in one large biopsy database, 182 of 742 OKCs were submitted with a preoperative clinical diagnosis of LPC.[8] Because OKC requires more aggressive surgical management and long-term surveillance, histopathological confirmation is mandatory for every lesion clinically suspected to be an LPC.
Histopathology
Epithelial lining
The cyst is lined by a thin, non-keratinized epithelium of one to five cell layers, resembling reduced enamel epithelium or cuboidal to low columnar cells.[2][3][12] The lining is characteristically non-inflammatory, distinguishing it from radicular cysts.[2]
Plaque-like thickenings
Focal epithelial thickenings (plaques) are the hallmark histological feature.[2][3][12] These nodular proliferations project into the cyst lumen or the fibrous wall and often contain glycogen-rich clear cells.[3][12] Glycogen positivity is present in the epithelium of the majority of cases, though not exclusively within the clear cells.[3]
Cyst wall
The fibrous connective tissue wall is typically thin, with minimal or absent inflammation.[7][12] Small islands of odontogenic epithelium may be present within the wall.[2]
Radiologic–pathologic correlation
The well-defined corticated radiographic margin corresponds to the thin fibrous capsule and the slow, non-aggressive growth pattern. The unilocular radiolucent interior reflects the single cystic cavity filled with thin fluid. Identification of multiple cystic compartments on histological examination—even when the radiographic appearance is unilocular—reclassifies the lesion as a botryoid odontogenic cyst, which carries a significantly higher recurrence rate.[2]
Differential histological considerations
- Odontogenic keratocyst: Distinguished by a parakeratinized stratified squamous epithelium with a palisaded basal layer.[4][11]
- Glandular odontogenic cyst: Shares plaque-like thickenings but additionally shows mucous cells, intraepithelial microcysts, ciliated cells, and hobnail cells. Rare LPC cases with glandular-type features have raised the question of a shared clinicopathologic spectrum.[3][10][11]
Management and prognosis
Treatment
Conservative surgical enucleation is the standard treatment for LPC.[2][5] Curettage is an alternative approach used in a minority of cases.[2] Tooth extraction is generally not required, as adjacent teeth are vital and can be preserved.[5]
Bone grafting
When enucleation creates a significant osseous defect with loss of the buccal cortical plate, guided bone regeneration with autologous/heterologous bone graft and a collagen membrane has been reported to achieve complete bone and periodontal healing.[5]
Recurrence
The recurrence rate for LPC is very low, approximately 2.4%.[2] No demographic or clinical factor has been shown to significantly influence recurrence.[2]
Surveillance
Radiographic follow-up is recommended for several years after surgery; most lesions show complete osseous healing within 6–12 months.[1] Long-term monitoring is warranted because rare late recurrences have been documented.[2]
Botryoid odontogenic cyst
The botryoid variant carries a substantially higher recurrence rate of approximately 21.7%, comparable to that of the odontogenic keratocyst.[2] Multilocular radiographic appearance is associated with increased recurrence risk.[2] Adjunctive measures after enucleation—such as peripheral ostectomy, cryotherapy, or Carnoy's solution—have been suggested for BOC, though evidence remains limited.[2]
Prognosis
Overall prognosis for LPC is excellent. Rare associations with ameloblastoma and squamous cell carcinoma have been reported, underscoring the importance of histopathological examination of all excised specimens.[1]
Special considerations
Relationship to gingival cyst of the adult
LPC and the gingival cyst of the adult are considered intraosseous and extraosseous manifestations of the same entity, respectively, sharing histological features and anatomic predilection.[2] Concurrent LPC and GCA in the same patient have been documented.[6] GCA presents as a small, soft-tissue swelling of the attached gingiva without a radiographic osseous component and is managed by simple excision with a similarly low recurrence rate.[2]
Histopathologic overlap with glandular odontogenic cyst
Rare LPC cases exhibit epithelial crypt formation and superficial palisaded columnar cells resembling glandular odontogenic cyst, raising the possibility of a shared clinicopathologic spectrum.[3] This overlap makes thorough histological sampling important, as glandular odontogenic cyst has a higher recurrence rate and may require more aggressive management.[2][10]