Why do these remnants proliferate? The origin of epithelial odontogenic neoplasms, hamartomas and cysts is inextricably bound up with a discussion of the parent cells of these lesions. Epithelial Remnants may develop into Cysts, Tumors, and Hamartomas.

1. Epithelial Remnants
Derivatives
Ahmad Amro Baradee

2. Definition
• The epithelial remnants are the rests of an epithelia
that served once as a meaningful tissue in embryonic
life or during the tooth formation.
• While this epithelial cells are supposed to disintegrate due
to ectomesenchymal invasion and/or programmed cell
death, others persist !!
• These Remnants may develop into Cysts, Tumors, and
Hamartomas.

5. Rests of Malassez

6. Reduced enamel epithelium

7. Rests of Serres
(Remnants of dental lamina)

8. Why do these remnants proliferate?
It is widely held that the majority of epithelial residues persist
throughout life as vital, by large inactive (resting) single cells or cell
clusters. Some of the cell rests seem to be triggered to proliferation by
hitherto unknown mechanisms (apart from instances of possible
inflammatory stimuli), resulting in production later in life of well-
recognized pathological entities.
The origin of epithelial odontogenic neoplasms, hamartomas and cysts is
inextricably bound up with a discussion of the parent cells of these
lesions.

9. • Radicular Cyst (+ Residual + Lateral)
Rests of
Malassez
• Paradental Cyst (Craig 1976)
• Calcifying Odontogenic Cyst(Prætorius et al. 1981)
• Dentigerous cyst
• Eruption Cyst
Reduced
enamel
epithelium
• Odontogenic keratocyst
• Lateral periodontal Cyst
• Gingival Cyst
• Glandular odontogenic Cyst
Rests of
Serres
cysts originated from odontogenic epithelial remnants

11. • Ameloblastomas
• Squamous Odontogenic Tumour
Rests of
Malassez
• Ameloblastomas
Reduced
enamel
epithelium
• Ameloblastomas (Peripheral Ameloblastoma)
• Squamous Odontogenic Tumour
• Calcifying Epithelial Odontogenic Tumor
• Adenomatoid Odontogenic Tumour
• Keratinising Cystic Odontogenic Tumour
• Odontogenic Gingival Epithelial Hamartoma
Rests of
Serres
Tumours originated from odontogenic epithelial remnants

13. • Arises from epithelial remnants of
the embryonic thyroglossal duct.
Thyroglossal
tract cyst
• Arises from epithelial remnants (of the
branchial arches or of salivary origin) within
cervical lymph nodes.
Branchial
cleft cyst
• Arises from epithelial remnants of the
embryonic nasopalatine duct.
Nasopalatine
Canal Cyst
Derivatives of other epithelial remnants in H&N

14. • Arises from epithelial remnants of the
lower part of the embryonic
nasolacrimal duct.
Nasolabial
Cyst
• Arises from epithelial remnants in the midline
during closure of 1st & 2nd branchial arches
Dermoid &
Epidermoid
cyst
• Arises from salivary epithelium
remnants in extracapsular lymphnodes
Warthin’s
Tumour
Derivatives of other epithelial remnants in H&N

15. In recent years, the existence of this group of lesions as separate entities has
been questioned and they were excluded from the 1992 WHO Classification of
epithelial jaw cysts (Kramer et al., 1992).
Previously, it had been thought that these cysts developed from epithelium
entrapped in the process of fusion of embryonic processes.
It is now believed that they represent :
- posterior extension of an incisive canal cyst in the case of median palatine cyst;
- anterior extension in the case of median alveolar cyst;
-and a range of other odontogenic cysts, frequently an odontogenic keratocyst, in
the case of the globulomaxillary cysts.
- Moreover, the so-called median alveolar cyst may also, in a number of instances,
be a keratocyst derived from dental lamina in the midline of the maxilla.
“NOTE ON THE SO-CALLED : MEDIAN PALATINE, MEDIAN
ALVEOLAR, MEDIAN MANDIBULAR AND GLOBULOMAXILLARY
CYSTS”

16. Radicular
Cyst
Paradental
Cyst
Dentigerous
Cyst
Eruption
Cyst

17. Odontogenic keratocyst
Lateral periodontal CystGingival Cyst
Glandular odontogenic Cyst

18. Ameloblastoma Calcifying Odontogenic Cyst
Peripheral AmeloblastomaSquamous Odontogenic Tumor

19. Calcifying Epithelial
Odontogenic Tumour
Adenomatoid
Odontogenic Tumour

20. Odontogenic Gingival
Epithelial Hamartoma
Dermoid & Epidermoid cyst
Keratinising Cystic
Odontogenic Tumour

21. Thyroglossal
tract cyst
Branchial cleft cyst
Nasolabial Cyst Nasopalatine Canal Cyst

22. References
• Philipsen HP, Reichart PA . The Development
and Fate of Epithelial Residues after
Completion of the Human Odontogenesis with
Special Reference to the Origins of Epithelial
Odontogenic Neoplasms, Hamartomas and
Cysts. Oral Biosci Med. 2004; 1: 171-179.
• Regezi JA, Sciubba JJ, Jordan RCK. Oral
Pathology: Clinical Pathologic Correlations, 5th
ed. St. Louis: Saunders; 2007.
• Soames JV, Southam JC. Oral pathology, 4th
ed. New York, Oxford University Press 2005.
• Shear M, Speight P. Cysts of the Oral and
Maxillofacial Regions 4th ed. Oxford: Blackwell
Munksgaard 2007.
• Neville BW, Damm DD, White DH. Color Atlas
of Clinical Oral Pathology 2nd ed. Ontario: BC
Decker 2003.

23. Questionnaire Session