Mandible / maxilla
Odontogenic cysts
Residual cyst

Author: Annie Morrison, M.D. (see Authors page)
Editor: Kelly R. Magliocca, D.D.S., M.P.H.

Revised: 21 June 2018, last major update April 2014

Copyright: (c) 2004-2018, PathologyOutlines.com, Inc.

PubMed Search: Residual cyst [title]

Cite this page: Morrison, A. Odontogenic cysts: residual cyst. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/mandiblemaxillaresidualcyst.html. Accessed August 16th, 2018.
Definition / general
  • Inflammatory fibrous and granulation tissue at the apex / periapical region of a tooth not removed / curetted at the time of dental extraction may give rise to residual cyst
Terminology
  • Odontogenic cysts: All odontogenic cysts found within the jawbones are inflammatory, developmental or less commonly (and more controversially) neoplastic
    • Source epithelium from which odontogenic cysts derive include:
      • Rests of Malassez
      • Dental lamina rests
      • Reduced enamel epithelium
      • Degenerated enamel organ
      • Rarely crevicular epithelium, or even surface epithelium
    • In general, inflammatory odontogenic cysts have proliferative epithelium, and developmental odontogenic cysts have a more uniform epithelium, although inflammation may lead to epithelial proliferation
      • Inflammatory odontogenic cysts appear to arise in response to inflammation
        • Clinicoradiographic variants include:
          • Apical (or periapical cyst, or radicular cyst) radicular cyst: present at root apex
          • Lateral radicular cyst: present at the opening of lateral accessory root canals
          • Residual cyst remains even after extraction of offending tooth
          • Buccal bifurcation cyst
      • Developmental odontogenic cysts: have unclear pathogenesis
    • Dental pulp:
    • Apical foramen: small opening at the apex of the tooth root that allows passage of neural and vascular supply of tooth
    • Periapical granuloma:
      • Apical / periapical acute or chronic inflammation admixed with fibrous or granulation tissue
      • Is devoid of epithelium (i.e. no cyst lining) which distinguishes it from a periapical cyst
      • Periapical granuloma is located at the apex of a necrotic or partially necrotic tooth
    • Epithelial rests of Malassez: discrete clusters of residual cells derived from Hertwig epithelial root sheath
      • Small spherules of 6 - 8 epithelial cells with high nuclear to cytoplasmic ratio
      • Little or no reverse polarity of cells
    • Reduced enamel epithelium (REE): ameloblastic and epithelial cells from the outer enamel that overly an unerrupted tooth, as the REE degenerates the underlying tooth is exposed
    • Dental lamina: band of epithelium that invades the underlying ectomesenchyme of the future dental arches at 6th week gestation
      • Is major component contributing to future tooth formation
    • Enamel organ: one recognizable step / stage in the formation of teeth
      • Formed from dental lamina
    • Crevicular epithelium: epithelium lining the inner aspect of the gingival sulcus
Epidemiology
  • 8% of all jaw cysts
Sites
  • Tooth bearing regions (or if dental extraction completed, former tooth bearing region) of maxilla and mandible
Pathophysiology
  • Pathophysiology of apical cyst and residual cyst similar
  • Activated T cells in periapical granulomas produce cytokines that act on rests of Malassez causing proliferation and altered differentiation leading to cyst formation
  • The proliferating epithelial masses become edematous, accumulate fluid and coalesce, forming microcysts containing epithelial and inflammatory cells
  • Cyst walls appear to have properties of a semi-permeable membrane, so osmosis contributes to increasing the size of cysts
  • Lytic products of the epithelial and inflammatory cells in the cyst cavity provide the greater numbers of smaller molecules which raise the osmotic pressure of the cyst fluid
Etiology
  • Trauma, carious lesion or bacterial colonization of developmental anomaly affecting tooth irreversibly injures dental pulp
  • Tooth pulp degenerates, inflammation ensues, and inflammatory products escape from tooth via apical foramen and access the surrounding / supporting periapical region of the jaw
Clinical features
  • Variable: range from asymptomatic and only incidentally detected on imaging, to expansion of affected jaw region, to pain and drainage
Diagnosis
  • By definition, the offending tooth has been removed, therefore the radiographic and clinical differential diagnosis of a radiolucent lesion in the jaws without a documented association to a tooth is broad
  • Diagnosis confirmed via removal of lesion and submission for microscopic examination
  • Ideal if have radiographic evidence of a necrotic or carious tooth (prior to dental extraction) to correlate
Radiology description
  • Round to oval radiolucency of variable size within the tooth bearing regions of jaws at the site of a previous tooth extraction
  • As the cyst ages, degeneration of the cellular contents within the lumen occasionally leads to dystrophic calcifications and radiographic opacities
Radiology images

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Residual jaw cyst

Prognostic factors
  • Vast majority have excellent prognosis
  • True residual cysts do not recur after appropriate treatment and are not premalignant - they have no increased risk of squamous cell carcinoma
  • Occasionally a secondary pathology, such as squamous cell carcinoma, arises from the epithelial lining of radicular, or other (odontogenic) gnathic cysts; careful patient questioning and clinical examination are necessary to exclude a primary oral mucosal neoplasm or metastases
    • Must also rule out an epithelial neoplasm which underwent secondary cystic change
    • Histological evidence of cyst lining with transition to epithelial dysplasia and infiltrating squamous carcinoma provides acceptable proof
Treatment
  • Any number of odontogenic and nonodontogenic cysts and tumors can mimic the appearance of a residual periapical cyst, therefore, these lesions should be excised surgically, even in the absence of symptoms
  • Residual cysts do not recur after appropriate management
  • Intraosseous fibrous scars are possible, especially when both cortical plates have been lost; this can give the appearance of a persistent radiolucent lesion
Clinical images

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Residual cyst in adentulous lower jaw

Microscopic (histologic) description
  • Epithelial lining of cyst: stratified squamous epithelium which may demonstrate exocytosis, spongiosis, or hyperplasia
    • Epithelium may be discontinuous in part and range in thickness from 1 to 50 cell layers
    • The majority are 6 - 20 cell layers thick
    • The nature of the lining may depend on the age or stage of development of the cyst, or on the intensity of the inflammation
    • In early cysts, the epithelial lining may be proliferative and show arcading with an intense associated inflammatory process but, as the cyst enlarges, the lining becomes quiescent and fairly regular with a certain degree of differentiation to resemble a simple stratified squamous epithelium
    • Rarely, scattered mucous cells or areas of ciliated pseudostratified columnar epithelium are noted
  • Cyst epithelium may also demonstrate:
    • Linear or arch shaped calcifications known as Rushton bodies
      • The bodies measure up to about 0.1 mm and are linear, straight or curved or of hairpin shape and sometimes they are concentrically laminated
      • Although the origin of hyaline bodies remains obscure, it is generally now thought that they represent a secretory product of odontogenic epithelium
    • Dystrophic calcifications
  • Cyst lumen may demonstrate fluid and cellular debris
  • Cyst lumen or wall may demonstrate:
    • Cholesterol clefts with multinucleated giant cells, red blood cells and areas of hemosiderin pigmentation
    • In histological sections, the cholesterol crystals are dissolved out and clefts are seen surrounded by dense aggregations of multinucleate giant cells
    • The cholesterol may be due to disintegrating red blood cells in a form that readily crystallizes and incites a foreign body giant cell reaction
  • Cyst wall may demonstrate
    • Dense fibrous connective tissue, often with an inflammatory infiltrate containing lymphocytes variably intermixed with neutrophils, plasma cells, histiocytes, and (rarely) mast cells and eosinophils
    • Occasionally will contain scattered hyaline bodies (pulse granuloma giant cell hyaline angiopathy)
      • These bodies appear as small circumscribed pools of eosinophilic material that exhibits a corrugated periphery of condensed collagen often surrounded by lymphocytes and multinucleated giant cells
    • Spicules of remodeling bone
    • Russell bodies are commonly seen
Microscopic (histologic) images

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Stratified squamous epithelial cyst lining

Differential diagnosis