Cysts

Cysts

1. Radicular Cysts

   • A radicular cyst is generally defined as a cyst arising from epithelial residues (cell rests of Malassez) in the periodontal ligament as a consequence of inflammation, usually following the death of the dental pulp.Radicular cysts are the most common odontogenic cystic lesions of inflammatory origin affecting the jaws.
   • Infection
     • Cysts can become infected causing spread of the infection, cellulitis, Ludwig's angina and even death. 
   • Jaw Fracture
     • Removal of enough cortical bone can weaken the jaw enough for physiological forces to cause jaw fracture
   • Jaw Expansion
     • As a radicular cyst expands it cause cause expansion of the cortical bone of the mandible or resorption. This causes a widening of the jaw localised to the area of the cyst
   • Asymptomatic
     • Commonly asymptomatic when small, unless they become large enough to cause expansion or become infected
   • DPT Radiograph
     • Frequently incidentally found on DPT radiographs, PA's can give more detail if able to capture on one film/plate
   • Pathological Examination
     • The only way to assure diagnosis is with histological examination. 
     • As a radicular cyst is diagnosed relatively easily these are usually enucleated without pathologocal examination.
   • Vitality Tests
     • To be a radicular cyst, the tooth of origin has to be non-vital
   • Darker shows cortex expansion
     • Most of the radio density comes from the cortical bone. Early lesions reside within medullarly bone. As these expand they resorb cortical bone. 
     • The darker and more radiolucent the cyst appears the further it has progressed.
   • Non-vital tooth
     • A radicular cyst can only occur around a non-vital tooth, therefore vitality testing is essential. 
     • A non vital tooth alone is not enough to make the diagnosis of a radicular cyst
   • Cortication at periphery
     • The bodies attempt to wall off the cyst leads to bone deposition that can be seen as a radio opaque line surrounding the cyst
   • Round in shape
     • Expand in three dimensions, like a balloon, in the early stages moving adjacent structures such as teeth, the progressing onto resorption of structures such as corticated bone
   • Expands buccally and lingually
     • Eventually causing expansion of the mandible/maxilla or resorption of the cortical bone
   • Commonly incidentally found
     • As the early stages of most cysts are asymptomatic, these are commonly incidentally picked up on DPT taken for other reasons 
   • Non-keratinised epithelial lining
     • No red surface stained keratin on the epithelium, therefore lining the lumen of a radicular cyst is non-keratinised epithelium
   • Fibroblasts and inflammatory cells
     • Once the cell wall is inflammed the fibroblasts become mixed with infiltrating inflammatory cells. 
     • More inflammaed due to being of inflammatory origin compared with dentigerous cysts
   • Wall thickness around 1mm
     • A broad assumption, but usually the cyst wall is around 1mm thick
   • Haemorrhage
     • Blood Spilt at Operation - A large infiltration of RBC is an artifact from the removal of the cyst causing bleeding into the tissues surrounding the cyst wall
     • This must be fresh haemorrhage as the erythrocytes are still visible at high power and have not yet undergone autolysis to release cholesterol and haemosiderin
   • Cyst wall constituents
     • Mainly fibroblasts making and maintaining collagen and connective tissue ground substance 
   • Cholesterol clefts
     • Slit like spaces hystologically are evidence of cholesterol left from RBC autolysis leaking into the wall of the cyst as a result of inflammation. 
     • The cholesterol in their wall becomes detached and crystalises. Organic solvents remove the cholesterol on slide preperations leaving these voids
   • Haemosiderin
     • A pigment produced by the breakdown of red blood cells during autolysis. 
     • This is the same pigment that causes the colouring of a bruise 
   • Extraction of tooth and enucleation
     • As these cysts are associated with non-vital teeth the presence of a radicular cyst dramatically reduces the success of RCT. Therefore teeth are commonly extracted and the cyst enucleated 
     • Enucleation - Surgical removal of a mass without cutting into or dissecting it
   • Periapical Granuloma
     • Common differential diagnosis - can often cause the same signs and symptoms, the only way to completely estabilish between the two is through hystological examination. 
     • Periapical Granuloma - a mass of granulation tissue, new connective tissue and tiny blood vessels
     • Small radicular cysts may be indistinguishable from periapical granulomas
   • PA Description
     • A radiolucent lesion in the right body of the maxilla extending from the apices of the upper central and lateral incisors almost to the lower border of the maxillary antrum.  
     • The shape is rounded, almost circular, about 1cm in diameter. It is unifomly radiolucent with a well defined margin and a mild degree of cortication surrounding the entire cyst.
     • There is loss of lamina dura around the root apices of the central and lateral incisors and possibly slight resorption of the tips of the roots. Both teeth have been root canal treated and have extensive restorations.
   • Unilocular
     • Consisting of only one cavity - single chambered.
   • Hydrostatic Pressure
     • Radicular cysts expand due to an internal hydrostatic pressure
   • Residual Cyst

2. Classification

   • Site
     • Location within jaw Location in relation to other structures Involvement with adjacent teeth
   • Shape
     • Unilocular Multilocular Round Well demarcated
   • Size
     • In cm x cm
   • Radio Density
     • Uniformity  Relative radiolucency Lamina dura  Cortication
   • Effect on adjacent structures
     • Resorption Displacement Removal of lamina dura ID canal Anturms Teeth 
   • Key
     • Radiographic signs that suggest diagnosis
     • Radiographic signs in common
     • Symptoms
     • Complications
     • Tests
     • Treatment
     • Common differential diagnosis
     • Histological Features
     • Other facts

3. Enlarge like a baloon

   • Circular expansion in three dimensions, dependent on surrounding structures

4. Uniformly radiolucent

5. Smooth Rounded Outlines

   • Well demarcated bounadries, unless infected or rapidly expanding 

6. Often Corticated

   • Thin white line at the boundary of a cyst formed of cortical bone

7. Early - Push Structures

   • Tilting of teeth  Movement of ID canal Pushing up of an antrum

8. Late - Resorb cortex and teeth

   • Root resorption Resorption of a lamina dura Destruction of ID canal Resorption of adjacent teeth

9. Dentigerous Cyst

   • A dentigerous cyst or follicular cyst is an odontogenic cyst - thought to be of developmental origin - associated with the crown of an unerupted (or partially erupted) tooth. The cyst cavity is lined by epithelial cells derived from the reduced enamel epithelium of the tooth forming organ.
   • Crown of unerupted tooth
     • One of the criteria for a dentigerous cyst is that it forms only on an unerupted or partially erupted tooth 
   • Mesial and distal extension
     • Commonly extend both mesially and distally to the affected unerupted tooth
   • Cemento-enamel junction lining attachment
     • The lining of the cysts connects to the tooth at the point of the cemento-enamel junction. The most characteristic of its features
   • Radiographs
     • Often commonly spotted on DPT radiographs, though a PA of the area can give more detail, unless the cyst is too large to fit onto a regular film/plate
   • Pathological examination to confirm diagnosis
     • The only way to insure a correct diagnosis is hystologically. Specimins can be sent to oral pathology for analysis 
   • Corticated margin
     • White radio opaque area surrounding a regular outline of the cyst
   • Non-keratinised
     • Develops from follicular epithelium, therefore it has more potential for growth, differentiation and degeneration than a radicular cyst. 
     • Typically bilaminar in appearance. Derived from reduced enamel epithelium 
   • Mucoepidermoid carcenoma
     • Due to its origin, and metaplastic ability it has a chance of developing into a mucoepidermoid carcenoma
   • Jaw fracture
     • Due to their ability to expand rapidly they may cause pathological fractures of the jaw bone.
   • Thin straw coloured fluid
     • On fine needle aspiration a thin straw coloured fluid will be found
   • Dental Follicle
     • A dental follicle surrounds teeth in physiology, the differentiation between the two is determined by size.  
     • Follicular space greather than 3mm is considered to be a dentigerous cyst.
     • The histological presence of mucous cells due to metaplasia can differentiate between a dental follicle and a dentigerous cyst
   • Unilocular
     • Consisting of only one cavity - Single chambered. 
     • Very rarely these can be multi-locular
   • Mandibular 3rd Molars Maxillar Canines
     • Most commonly affected teeth. 
     • Dentigerous cysts very rarely affect deciduous teeth 
   • Marsupialization
     • Large cysts are drained by cutting a slit into the cyst and suturing the edges to the surrounding tissue to make a continuous surface from the exterior surface to the interior surface. This can therefore drain freely
   • Excision
     • Smaller cysts -  unlike enucleation, the cyst may be cut during removal. The associated tooth is usually removed at the same time 
   • PA Description
     • A lesion in the lower ramus and retromolar region of the right mandible, approximately 2cm by 1cm, above the inferior dental canal and associated with the crown of the unerupted lower third molar, which is impacted vertically against the cortex of the anterior ramus. 
     • The lesion is uniformly radiolucent and has a well-defined smooth outline and corticated margin superiorly, but is less well demarcated inferiorly. 
     • There has been root resorption arround the third molar or the roots have yet to develop.
   • Less inflammation
     • Less inflammation than a radicular cyst due to it not being of inflammatory origin. Usually only inflammation in association with cholesterol clefts
   • Mucous cells
     • Differentiation due to metaplasia, mucous cells are not usually present in odontogenic epithelium. More common in the maxilla.  
     • Light blue bubbly cells within the epithelial lining.
     • Can be an indication of VERY rare salivary gland neoplasms to find these type of cells in this area.
   • Epithelial thickening
     • In sites adjacent to haemorrhage due to inflammation epithelial thickening can occur. 
     • Due to cytokine release from inflammatory cells inducing hyperplasia
     • Can also be due to compression against the periostium causing traumatisation, resulting in loss of the typical bilaminar epithelial appearance 
     • Inflammation makes histological differentiation of radicular and dentigerous cysts almost impossible. Therefore site is important
   • Bi-laminar
     • Diagnostic of dentigerous cysts, bi-laminar epithelium. Two layers.
     • One layer of small basal cells and another of cuboidal surface layer
   • Cholesterol clefts
     • Slit like spaces hystologically are evidence of cholesterol left from RBC autolysis leaking into the wall of the cyst as a result of inflammation. 
     • The cholesterol in their wall becomes detached and crystalises. Organic solvents remove the cholesterol on slide preperations leaving these voids
   • Haemorrhage
     • Blood Spilt at Operation - A large infiltration of RBC is an artifact from the removal of the cyst causing bleeding into the tissues surrounding the cyst wall
     • This must be fresh haemorrhage as the erythrocytes are still visible at high power
   • Vital teeth
     • As these are unerupted or partially erupted teeth they are always vital
   • AKA Follicular Cyst

10. Incisive Canal Cyst

    • Surround the incisive canal
      • Can only surround the incisive canal, and there for is one of the most important distinguishing features
      • As the cyst enlarges it can expand asymetrically making the diagnosis more difficult
    • Radiographs
      • DPT may be inaccurate as the location is generally outside the plane of focus. Therefore additional radiographs are required to assess its extent. 
      • Periapicals and upper standard occlusals can help to determine if the cyst is around the incisors or palatal to them 
    • Root displacement
      • Commonly displaces roots of the upper anterior teeth 
    • Non-odontogenic
      • Non-tooth associated - does not develop from the root or crown of a tooth 
    • Hydrostatic pressure
      • Cyst enlarges under hydrostatic pressure, therefore the origin of the cyst can usually be found towards the centre of the lesion. Which in this case lies on the incisive canal
    • Lamina dura loss
      • Pressure on the roots causes loss of the lamina dura 
      • Lamina dura - Bundle bone that lines the tooth socket next to the periodontal ligament where Sharpey's fibres of the peridontium perforate 
    • Root Resorption
      • Can cause root resorption in the late stages generally causes a small amount of root tip resorption 
    • Vital Teeth
      • Always associated with vital teeth, an incisive canal cyst cannot be confirmed without affected teeth vitality testing 
    • Cortication
      • Cortication would be expected and the outline well defined, if there is no cortication this could be due to inflammation or infection when the edge becomes fuzzy radiographically
    • AKA Nasopalatine Duct Cyst
      • Also known as Nasopalatine duct cyst due to its relativity to this duct 
    • Residual ductal epithelium
      • Nasopalatine duct epithelium usually regress in fetal life. The persistance of ductal epithelium results in the formation of a cyst 
      • Humans do not usually have a nasopalatine duct as it degenerates before birth
    • Most common non-odontogenic cyst
      • Most common cyst that is not of tooth origin 
    • Swelling
      • Swelling in the anterior palate 
    • Pain
      • Can cause palatal pain and drainage
    • Incisive foramen
      • An incisive foramen is rarely bigger than 6mm, though you cannot use size alone to distinguish between an incisive foramed and an incisive canal cyst
    • Ciliated Respiratory epithelium
      • Arounf 30% of cases histologically contain respiratory epithelium. Difficult to find as it is non keratinised and therefore damages easily on removal
      • Pseudostratified ciliated columnar epithelium, due to their origin of connecting the mouth and nose 
    • Unilocular
      • Consisting of only one cavity - Single chambered. 
    • Enucleation
      • Usually curative, recurrence is rare histological confirmation s recommended 
      • Enucleation - Surgical removal of a mass without cutting into or dissecting it
    • Pathological Examination
      • Recommended to confirm diagnosis after enucleation
    • Periapical granuloma
      • Tooth associated usually at the apex of the tooth. Histological confirmation of the two
    • Schwannoma
      • Within the incisive canal region. Benign tumour of the schwann cells. Most common benign tumour of the peripheral nerves 
    • Site of Origin
      • More important for diagnosis, as histologically difficult to differentiate from other types of cyst
    • Stratified non-keratinised epithelium
      • With a mixture of respiratory epithelium 'pseudostratified ciliated columnar epithelium'
    • Mucoid glands
      • Found in the wall of pseudostratified ciliated columnar epithelium due to being respiratory epithelium derived 
    • Neurovascular bundle
      • Due to the long sphenopalatine nerve running through the incisive canal, the enucleated specimen may contain nerve bundes associated with blood vessels 
    • Little inflammation
      • Due to not being of inflammatory origin, the histological slides will show little inflammatory infiltrate 

11. Odontogenic Keratocyst

    • AKA Keratocystic Odontogenic tumour
      • Some feel it is a benign neoplasm, hence the differentiation in the name 
    • Vitality test
      • A vital tooth rules out radicular cysts
    • Lamina dura Loss
      • Can be the sign of any cyst type, but odontogenic keratocysts usually do not cause root resorption due to the low pressure on expansion
    • No root resorption
      • Low pressure expansion of the cyst means no root resorption on affected teeth
    • Low pressure expansion
      • Unlike most other cysts, odontogenic keratocysts do not cause root resorption due to low pressure expansion and are generally not as circular.
    • Peripheral cortication
      • Along with a smooth rounded periphery
    • No tooth displacement
      • Due to not expanding due to internal pressure, these do not displace teeth until very late stages
    • Path of least resistance
      • Does not expand by internal pressure by the epithelium grows and burrows insidiously along the path of least resistance. Thesefore these rarely expand cortical bone and follow medullary bone.
    • Multilocular
      • Usually have a septum dividing the created cavity. Can be unilocular
    • Tendency to recur
      • As these have a tendencey to recur they have to be resected if large enough or enucleated. Then treated with Carnoy's solution
    • Resection
      • Large odontogenic keratocysts need to be resected (removal of the cyst and some of the normal tissue around it to confirm complete removal)
    • Enucleation
      • Smaller cysts can be enucleated then treated with carnoy's solution. Which is a fixative that kills residual cyst lining which makes it firmer and easier to peel away from the bone and remove
    • Carnoy's Solution
      • Used to aid enucleation, a fixative that makes the cyst firmer and easier to peel away from bone and remove
    • Biopsy is always required
      • To determine its cause due to its increased chance of recurance
    • Posterior mandible
      • Most commonly affects the posterior mandible
    • Flat basement membrane
      • Without the usual rete pegs usually associated with keratinised tissue
    • Corrugated keratinised layer
      • A red staining layer of keratinised tissue is defining histologically for an odontogenic keratocyst
    • Parakeratin
      • Occasionally a nucleus remains in the surface layers
    • No granular cell layer
      • Unlike most epithelium, there is no granular cell layer
    • Palisaded basal cells
      • Long type cells laying perpendicular to the adjacent tissue. These look like preameloblasts
    • Reverse polarity cells
      • Cells facing in the oposite direction with their nucleus away from the basal membrane, just like ameloblasts which do this to produce enamel at the other end
    • Epithelium 5-12 cells thick
    • Uninflammed fibrous wall
      • Usually very thin, and tears easily, possibly contributing to the high rate of recurrance
    • Split epithelium
      • The epithelium often splits from the fibrous wall, possibly a factor than contributes to the reoccurence
    • Mitotic figures
      • Due to expansion by epithelial invasion, these have a higher growth rate than other cysts so many cells may be found during mitosis
    • Histological diagnosis
      • Only cyst that can be diagnosed entirely histologically
    • Ameloblastoma
      • Next most likely diagnosis for similar radiographic findings
    • Hyaline bodies
      • Red string like structures between cells.
    • Basal cell naevus
      • A syndrome where 75% of patients have odontogenic keratocysts. 
      • Caused by a mutation in the patched gene

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