1. Chapter 15: Odontogenic cysts and tumors

2. Overview:
Odontogenic cysts & tumors arise from the odontogenic apparatus.
The odontogenic apparatus consists of:
Epithelium:
• Remnants of dental lamina
• Reduced enamel epithelium
• Odontogenic rests
• Lining of odontogenic cysts
• Basal cell layer of oral mucosa
Ectomesenchyme:
• Dental papilla
Q: What is a cyst?
A: An abnormal space within tissue lined by epithelium.
Q: Name some “cysts” that are not really cysts:
A: Aneurysmal bone cyst, Stafne bone cyst, Traumatic bone cyst,
Simple bone cyst, Eruption cyst
Q: Why are they not cysts?
A: No epithelial lining!

3. The Cysts and Tumors of Chapter 15:
Odontogenic cysts:
Inflammatory:
•Periapical (radicular) cyst
•Residual periapical (radicular) cyst
•Buccal bifurcation cyst (usually first
molars)
–Paradental cysts (partially
erupted third molars
Developmental:
•Dentigerous cyst
•Odontogenic keratocyst (KOT)
•Orthokeratinized odontogenic cyst
•Gingival (alveolar) cyst of the newborn
•Gingival cyst of the adult
•Lateral periodontal cyst
•Calcifying odontogenic (Gorlin) cyst
•Glandular odontogenic cyst
•Eruption cyst
Odontogenic Tumors:
Epithelial Tumors:
•Ameloblastoma
•Adenomatoid odontogenic tumor
•Calcifying epithelial odontogenic
tumor (Pindborg tumor)
•Squamous odontogenic tumor
•Clear cell odontogenic carcinoma
Ectomesenchymal Tumors:
•Odontogenic myxoma
•Granular cell odontogenic tumor
•Central odontogenic fibroma
•Cementoblastoma
Mixed Odontogenic Tumors:
• Odontoma
–Compound
–Complex
• Ameloblastic fibroma
• Ameloblastic fibro-odontoma
• Ameloblastic fibrosarcoma
• Odontoameloblastoma

5. Periapical cyst or granuloma (chronic localized osteitis)
▪ Impossible to tell radiographically which one it is – only histologically, so you
must include both in your differential diagnosis.
Q: Why does a periapical cyst form instead of just a granuloma?
A: If by chance there are Rests of Malassez in the area of inflammation.
▪ The rest cells proliferate due to the inflammation
▪ The ball of cells gets too large, cells in the center die, center then has a higher protein
concentration, water rushes in to equalize the osmotic pressure.
▪ Osmotic pressure can continue to grow the cyst independent of the inflammation.
Other unilocular radiolucencies located periapically:
▪ (early) periapical cemento-osseous dysplasia – teeth are vital
▪ Dentin dysplasia type I – teeth are vital, multiple radiolucencies
With a periapical cyst or granuloma, the tooth is NON-VITAL
Take a vitality test!!
▪ Tx for a non-vital tooth is root canal.
▪ Must biopsy a radiolucent lesion beneath a vital tooth.

7. Dentigerous cyst ▪ Radiolucency associated with an unerupted tooth
▪ encloses the crown of the unerupted tooth and is attached at the CEJ
▪ Most common developmental odontogenic cyst
▪ Should be the first differential diagnosis for any radiolucency associated with an
unerupted tooth
Others: Odontogenic Keratocyst (KOT), Ameloblastoma

8. (Vital teeth)

9. Odontogenic Keratocyst (Keratocystic Odontogenic Tumor)
Can be in the location of ANY other type of odontogenic cyst or can be isolated in the jaws!
• a benign uni-or multicystic, intraosseous tumor of odontogenic origin
• lining is parakeratinized stratified squamous epithelium
• potential aggressive, infiltrative behavior
• solitary or multiple (multiple usually related to Gorlin syndrome)
Three important things associated with this diagnosis:
1. High recurrence rate (up to 60%)
2. Highly aggressive (now considered by W.H.O. to be an odontogenic tumor)
3. Relation to Gorlin syndrome
Arises from the dental lamina or its remnants
PTCH gene is a significant factor in the development of KOT

10. Nevoid Basal Cell Carcinoma Syndrome (Gorlin Syndrome)
• Multiple basal cell carcinomas
• Multiple jaw cysts (odontogenic keratocysts)
• Numerous bone abnormalities including bifid ribs, intracranial calcification,
vertebral anomalies
PTCH gene has been mapped to chromosome 9q site of Gorlin Syndrome
Anyone with multiple KOTs should be tested for Gorlin Syndrome

12. Lateral Periodontal Cyst
▪ The lateral periodontal cyst is generally quite small and well demarcated. It occurs most frequently in the mandibular bicuspid area adjacent to vital teeth.
Radiolucencies are generally small and ovoid
▪ Derived from remnants of the dental lamina
Tx: conservative enucleation
▪ Considered to be the intrabony counterpart to the Adult Gingival Cyst

14. Biopsy:

15. Calcifying Cystic Odontogenic Tumor (Gorlin’s cyst)
• Uncommon lesion that demonstrates considerable histopathologic diversity and
variable clinical behavior
• Can be unilocular or multilocular, can be associated with an unerupted tooth
Tx: simple surgical excision, prognosis is usually good
“Ghost” cells calcify

17. Biopsy:

18. Ameloblastoma
• Slow growing, non-painful, multilocular, radiolucent lesion
• Most common clinically significant odontogenic tumor
• Epithelial origin
• Average age = 33
Tx: resection beyond the margins
(tumor is to difficult to remove, and tends to recur)
Peripheral, palisaded cells with nuclei polarized away from the basement membrane

20. Unicystic Ameloblastoma
• Account for 10-15% of intraosseous ameloblastomas
• Usually occur in younger patients
•Because all of the ameloblastoma is inside the lumen of the cyst, Tx. is removal of the cyst (not jaw resection)
But… If ameloblastoma is in the wall of the cyst, treatment must be standard for ameloblastoma = resection
Can often resemble a dentigerous cyst around an unerupted 3rd molar

22. Biopsy:

23. Adenomatoid Odontogenic Tumor “A.O.T”
•Young patients
•Anterior jaws
•Usually associated with impacted teeth
•Easily removed, therefore small chance of recurrence
Tx: curettage
“Gland-like” structures in a solid
tumor of odontogenic cells

25. Biopsy:

26. Calcifying Epithelial Odontogenic Tumor (Pindborg Tumor)
• Uncommon (less than 200 cases reported to date)
Radiolucent lesion with calcified radiopacities inside
(calcifications are most often seen in association with an impacted tooth)
Tx: local resection
Protein in the “amyloid”
areas is a new, recently
discovered protein
*With Congo Red stain the
lesion will exhibit apple-green
bifringence when viewed with
polarized light

28. Ameloblastic Fibroma Tumor of both ectodermal and epithelial layers
• Younger patients
• Not generally aggressive, easily removed if discovered and treated early
If the lesion contains calcifications, then it is an Ameloblastic Fibro-odontoma

29. A. B.

30. Odontoma “Tooth tumor” – mixed odontogenic tumor
A.) Compound: look like little teeth, tooth material is in correct relation
B.) Complex: everything mixed together, no normal relation of tooth material
Tx: simple local excision – prognosis is excellent

32. Biopsy:

33. Odontogenic Myxoma • “soap bubble” appearance
• aggressive- may displace or cause resorption of teeth
• Derived from odontogenic ectomesenchyme
Tx: small lesions can be treated by curattage, but since the lesion is not encapsulated, the site should be closely monitored, and large lesions may require more extensive resection.
Hisologically odontogenic myxomas look just like dental papilla