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Oral Pathology Exam 3 > 4. Odontogenic Cysts > Flashcards

4. Odontogenic Cysts Flashcards

1
Q

What is an Odontogenic Cyst?

A
  • Pathologic cavity lined by epithelium derived from tooth-formative cells
    • Must be a cavity, and lined by epithelium to be a true cyst
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2
Q

What are the 4 possible sources of odontogenic epithelium?

A
  1. Dental lamina gets left in the jaws and gingiva
  2. Rests of Malassez
    • ​​Broken off pieces of Hertwig’s sheath that reside in PDL
  3. REE that lines the follicle
  4. Rests of Serres
    • ​​Small buds of resting odontogenic epithelium (dental lamina) that live in the gingiva
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3
Q

What is the most common odontogenic cyst?

A

Periapical Cyst

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4
Q

How do PA cysts develop and grow? (3)

A
  • Within pre-existing PA Granuloma from inflammatory stimulation of rests of Malassez
  • As the rests proliferate, the central epithelium degenerates (becomes necrotic) to form the cyst lining
  • Continues to grow from hemodynamic pressure = Oncotic Edema
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5
Q

Location of Periapical Cyst

A

ONLY around the apex of a non-vital root

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6
Q

What age group is affected by Periapical Cysts?

A

Adults

  • Rare in children, because a rxn to a non-vital deciduous tooth occurs in the furcation, not the apex.
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7
Q

What is the radiographic appearance of Periapical Cysts? (4)

A
  • Well-demarcated, spherical RL
  • Epicentered over apex of non-vital root
  • Absent lamina dura around apex
  • No PDL space
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8
Q

Which are more likely to be larger, cysts or granulomas?

A

Cysts

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9
Q

What is the clinical presentation of Periapical Cysts? (4)

A
  • Typically no signs or symptoms
  • May show mild discomfort to percussion or tooth “feeling different” from adjacent teeth, not pain.
  • Painful ONLY if secondarily infected, typical pa cysts are not infections
  • Some are large, expansile, and produce flutuant swelling, and can erode bone
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10
Q

What is the Histology of a Periapical Cyst? (2)

A
  • Stratified squamous, non-keratinizing epithelium overlying an inflammed collagenous cyst wall
  • Inflammatory Changes due to:
    • Epithelial Rxn
      • ​Thinned out and hyperplastic epithelium
    • Cholesterol​
      • _​_Deposited as slits in CT, “white crystal” appearance
      • Gets gobbled up by macs, forming foam cells
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11
Q

What is the treatment for a Periapical Cyst? (3)

A
  • Root Canal Therapy with follow-up to ensure resolution
  • Apical Surgery with Biopsy if …
    • RL remains > 6 months OR grows
    • Failed RCT
    • Misdiagnosis
  • If the pt denies RCT, extraction of tooth
    • Biopsy of curetted periapical soft tissue
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12
Q

What is the rationale for treating Periapical Cysts?

A
  • Known to become malignant SCCA
  • Other pathology can mimic pa cysts, rct done on vital teeth all the time
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13
Q

What is the 4th most common odontogenic cyst?

A

Residual Cyst

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14
Q

What is the pathogenesis of a Residual Cyst? (3)

A
  • Formed from rest of Malassez
  • A cyst that remains after the associated tooth is removed
    • ​Most are Periapical Cysts that were left after the tooth was extracted
  • No relationship to teeth
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15
Q

What is the most likely odontogenic cyst to transform into SCCA?

A

Residual Cyst

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16
Q

What is the 4th most common odontogenic cyst?

A

Residual Cyst

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17
Q

What is the only way to diagnose a Residual Cyst?

A

Histology + No assoc tooth

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18
Q

What is the 2nd most common odontogenic cyst?

A

Dentingerous Cyst

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19
Q

What is a Dentingerous Cyst?

A

Developmental cyst of the follicle of an unerupted or impacted tooth

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20
Q

What is the cyst lining of a Dentingerous Cyst derived from?

A

REE lining the follicle

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21
Q

What is the cyst wall of a Dentingerous Cyst derived from?

A

CT of the follicular sac

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22
Q

What age is affected by Dentingerous Cysts?

A
  • Any age, but peaks in 3rd decade
  • Rare in children
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23
Q

Where are Dentingerous Cysts found, what is the most common of the locations?

A

Areas most likely to have impacted teeth

  1. Mandibular 3rd Molar
  2. Canines
  3. Maxillary 3rd Molars
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24
Q

What is the radiographic appearance of Dentingerous Cysts? (4)

A
  • Circular, uni-locular, peri-coronal RL, around an impacted OR unerupted tooth
  • NEVER multilocular
  • Attaches at cervical area of crown at acute angle
  • Can get huge and fill up entire ramus
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25
Q

What is the clinical presentation of a dentingerous cyst? (3)

A
  • Most cases asymptomatic
  • Large examples can cause swelling
  • Can become secondarily infected and inflamed
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26
Q

What is the Histology of Dentingerous Cyst? (3,1)

A
  • Identical to PA Cyst
  • May show secondarily inflammation if it breaks through the bone (food and other stuff can enter the cyst)
  • REE is pluripotent and can transform into more significant pathology
    • REE commonly produces mucous cells in Dentingerous Cysts
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27
Q

What complications are associated with Dentingerous Cysts? (4)

A
  • Malignant Transformation due to REE pluripotent potential
    • Ameloblastoma can arise in pre-existing dentingerous cysts
    • MEC that started out centrally (jaws) in a DC
  • Infection
    • DC’s that become infected can transform into SCCA
  • Resorption of roots or PD of 2nd molar
  • Pathologic fracture at the angle of the jaw, if big enough
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28
Q

What is the treatment and prognosis for a Dentingerous Cyst?

A
  • Enucleation (shell it out) and biopsy to rule out pathology
  • No recurrences if completely removed
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29
Q

What population are Eruption Cysts found in?

A

Kids

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30
Q

What is the pathogenesis of Eruption Cysts?

A

Dentingerous Cyst that forms in soft tissue during tooth eruption

  • Area of RL seen as DC is formed
  • As eruption occurs the tooth pushes the cyst to the surface
31
Q

Where are Eruption Cysts found? (2)

A
  • 1st molars
  • Maxillary Central Incisors
32
Q

What is the clinical appearance of an Eruption Cyst?

A

Fluctuant, soft blue dome, before the tooth erupts

33
Q

What is a Hyperplastic Dental Follicle?

A

Not a Cyst

Represents a thickening of the fibrous wall of the dental follicle

34
Q

What is the size of a Hyperplastic Dental Follicle?

A

Small, 2-4mm from the tooth to the lesion border

If > 5mm = Dentingerous Cyst

35
Q

What is the histology of a Hyperplastic Dental Follicle? (3)

A
  • Normal follicular REE lining, and fibrous wall thickened with myxoid ground substance
  • No squamous epithelium
  • Can look like an Odontogenic Myxoma
36
Q

What is the least common odontogenic cyst?

A

Lateral Periodontal Cyst (2%)

37
Q

Where are Lateral Periodontal Cysts found?

A
  • Always appears in interradicular bone, in-between 2 teeth
  • Only 2 Locations
    • Mandibular Premolar Area (75%)
      • Has to have a pm on at least 1 side
    • Maxillary Incisor Area (20%)
38
Q

What population are Lateral Periodontal Cysts most common in?

A

Males > 40 yrs

39
Q

What are Lateral Periodontal Cysts derived from?

A

Post-functional dental lamina sitting in bone

40
Q

What is the diagnostic radiographic appearance of Lateral Periodontal Cysts? (4)

A
  • Small (4-10mm) innocuous cyst
  • Circular RL, with corticated upper border within interradicular bone
  • Associated with vital teeth
    • ​Lamina dura and PDL space are intact
  • No swelling or symptoms
41
Q

What is the super diagnostic histology of lateral periodontal cysts? (3)

A
  • Cyst wall = thin, densely collagenous non-inflammatory
  • Cuboidal odontogenic epithelial lining,
  • With focal (mural) thickenings of plaques of swirled/clear cells that project into lumen
42
Q

What is the treatment for Lateral Periodontal Cysts? (3)

A
  • Completely Innocuous
    • Will not grow, cause any symptoms, or turn into cancer
  • Enucleate without harming adjacent teeth
  • Must biopsy, counterintuitive
    • 25% that radiographically look like LPC are actually OKC’s under the microscope
43
Q

What is the only cyst exclusively in soft tissue (not in bone)?

A

Gingival Cyst

44
Q

What is the gingival cyst derived from?

A

rests of Serres that live in gingiva

Same cells that cause LPC, but these aren’t in bone

45
Q

Where are Gingival Cysts found?

A
  • ONLY on the buccal aspect of mandibular premolar area
  • Occasionally in upper incisor area
  • Soft tissue equivalent of the LPC, same location
46
Q

What population is affected by gingival cysts?

A

ONLY in Adults

47
Q

What is the 3rd most common cyst?

A

ODontogenic Keratocyst (OKC)

48
Q

What is the clinical presentation of an Odontogenic Keratocyst?

A
  • An aggressive, cystic neoplasm that continues to expand within medullary bone, producing a large destructive lesion
    • ​Expansion due to active growth, rather than inflammation/hemodynamic causes
49
Q

What are OKCs derived from?

A

rests of dental lamina

Not post-functional dental lamina like in LPC, this still has growth potential

50
Q

What population do OKCs occur in?

A

Any age, prefers Adults

51
Q

What location do OKC’s occur in?

A
  • Any location of tooth formative epithelium
    • Prefers mandibular 3rd molar region (50%)
  • Never begins in the ramus, below the level of the mand canal
    • It may expand there eventually
52
Q

In the mandibular 3rd molar region what do OKC’s mimic?

A

Dentingerous Cysts

53
Q

What percent of Dentingerous Cysts were dx incorrectly and are actually OKC’s?

A

9%

54
Q

What percent of Periapical Cysts were dx incorrectly and are actually OKC’s?

A

<1%

This is actually alot because PA Cysts are so frequent

55
Q

What percent of Residual Cysts were dx incorrectly and are actually OKC’s?

A

12%

56
Q

What percent of Lateral Periodontal Cysts were dx incorrectly and are actually OKC’s?

A

25%

  • This is why we do biopsies on them, even though they are innocuous.
  • A radiograph isn’t sufficient, but their histology is diagnostic.
57
Q

What occurs when OKCs are left alone?

A
  • They become multilocular RL
  • They can mimic Ameloblastomas or Myxomas
    • OKCs are more common than both of these combined
58
Q

What are the Characteristic Histologic Findings of a non-inflamed OKC? (5)

A
  • Thin epithelium w/o rete ridges
    • Flat, no rete ridges to hold it into the CT so it sloughs away from CT
  • Striking BASAL CELL layer - hyperchromatic & polarized
  • Persistence of crowded basal cells into stratum spinosum
  • Abrupt transition to refractile, glassy like parakeratin with a corrugated surface
  • Mitotic activity epithelium is expanding because it wants to
59
Q

How does the histology of Odontogenic Keratocysts (OKC) change when it becomes inflammed? (4)

A
  • Cyst Lining:
    • Loses keratin
    • Thickens
    • Loses hyperchromatic basal layer
    • Develops rete ridges
  • Resembles other non-descript cysts
  • Cannot be dx histologically
60
Q

What occurs when an odontogenic keratocyst has keratin? (4)

A
  • More aggressive
  • Grew bigger
  • Harder to remove
  • Recur with a vengance
61
Q

What is the recurrence for Odontogenic Keratocysts? (5)

A

30% Recurrence

  • Difficulty in removal
    • _​_The thin epithelium sloughs off as soon as you touch it
    • Larger ones are multilocular
  • Neoplastic potential of remaining epithelium
    • The lining just wants to keep growing
  • 10 yr follow-up, it has been known to recur up till 25 yrs
  • Higher recurrence than everything except Ameloblastoma (55%)
  • This is the ONLY odontogenic cyst that recurs
62
Q

What treatment is preferred on larger Odontogenic Keratocysts (OKC)?

A

Partsch Procedure

  1. Decompress cyst
  2. Curette as much as possible
  3. Leave it open to allow drainage
  4. Bone begins to fill in and it will be smaller
  5. Go back in later on and remove the rest
  6. Sterilize peripheral bone

Similar to what is done for Ameloblastoma’s

63
Q

In rare cases what has odontogenic keratocysts transformed into?

A
  • Ameloblastoma
  • SCCA
64
Q

What are Odontogenic Keratocysts associated with?

A

Basal Cell Nevus Syndrome

65
Q

What lesion is 10x less common than OKCs and produces ONLY orthokeratin?

A

Orthokeratinized Odontogenic Cyst

66
Q

What population is most affected by Orthokeratinized Odontogenic Cysts?

A

Young-adult, males (2:1)

  • Lateral Periodontal Cyst is the other cyst that prefers males, but they will be > 40 yrs old
67
Q

What are 2 characteristics of Orthokeratinized Odontogenic Cysts?

A
  • 2/3 in a Dentingerous Relationship
    • Mimic a big dentingerous cyst
  • Unilocular
68
Q

What is the histology of the Orthokeratinized Odontogenic Cyst? (4)

A
  • Basal Cells are:
    • Flat
    • Non-proliferative
    • Innocuous
    • Inconspiciuous

Exact opposite of OKC, whose basal cells are proliferative, polarized, and hyperchromatic

69
Q

What is the recurrence of Orthokeratinized Odontogenic Cysts?

A

2% Recurrence

Much less aggressive than OKC’s (recur in 30%)

70
Q

What is the etiology of Basal Cell Nevus Syndrome?

A

Autosomal Dominant

High penetrance, with variable expressivity

Relatively common

71
Q

What are the defining characteristics of Basal Cell Nevus Syndrome? (11)

A
  1. Multiple BCCA in childhood
    • Non-sunexposed areas (arms, chest, back)
  2. Multiple OKC’s ​​
  3. Palmar Pitting in 65%
  4. Hypertelorism
  5. Depressed mid-face
  6. Saddle Nose - widened nasal bridge
  7. Relative frontal bossing
  8. Relative mandibular prognathism
  9. Calcification of falx cerebri - midline
  10. Bifid ribs
  • ​Mental Retardation/Schizophrenia - some may have Hydrocephalus
72
Q

In Basal Cell Nevus Syndrome what are the skeletal findings due to?

A

Peripheral resistance to PTH

73
Q

What is the most common finding in the jaws of a pt with Basal Cell Nevus Syndrome?

A

Multiple OKCs

74
Q

What is the treatment for Basal Cell Nevus Syndrome? (4)

A
  • Topical Chemotherapy (5 FU)
    • Watch for and eliminate BCCA when they 1st occur (superficial, hasn’t invaded yet)
    • If you do not tx BCCA they can become aggressive and coalesce
  • Remove OKCs until they stop developing
  • Genetic Couseling + examination of family members
  • Continual Follow-Up
    • ​In rare cases they can develop a Medulloblastoma Brain Tumor

Oral Pathology Exam 3 (8 decks)

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