1. Cysts of the head & neck
Cyst : is a pathologic cavity lined by epithelium ,contains fluid or semisolid material .

2. General notes
Cysts that possess an epithelial lining are called true cysts.
Pseudocysts are lesions such as traumatic bone cysts , aneurismal bone cyst ,& static bone cyst .
The epithelial lining could be : keratinized , non keratinized , stratified squamous , pseudostratified , columnar , cuboidal.
The wall is composed of connective tissue containing fibroblasts & blood vessels .
Cysts often exhibit various degrees of inflammation . cysts are often destructive.

3. Epithelial rest of malassiz part of the periodontal ligament cells around a tooth. They are discrete clusters of residual cells from Hertwig's epithelial root sheath (HERS) that didn't completely disappear. Reduced enamel epithelium overlies a developing tooth and is formed by two layers: a layer of ameloblast cells and the adjacent layer of cuboidal cells (outer enamel epithelium) from the dental lamina. As the cells of the reduced enamel epithelium degenerate, the tooth is revealed progressively with its eruption into the mouth. Epithelial rests of Serres remnants of dental lamina epithelium entrapped within the gingiva.

4. Classification of cysts of the jaws (WHO — modified) Developmental cysts 1.Odontogenic Dentigerous (follicular) cyst. Odontogenic keratocyst ('primordial' cyst). Eruption cyst. Lateral periodontal cyst. Gingival cyst of adults. 'Gingival cysts' of infants (Epstein pearls). Glandular odontogenic(sialo-odontogenic cyst). 2.Non-odontogenic cysts Nasopalatine duct cyst. Nasolabial cyst. Inflammatory odontogenic cysts Radicular. Residual. Lateral. Paradental.

6. Key features of the jaw cyst 1
Key features of the jaw cyst 1.Form sharply-defined radiolucencies with smooth borders 2.Fluid may be aspirated and thin-walled cysts may be transilluminated 3.Grow slowly, displacing rather than resorbing teeth 4.Symptomless unless infected and are frequently chance radiographic findings 5.Rarely large enough to cause pathological fracture 6.Form compressible and fluctuant swellings if extending into soft tissues 7.Appear bluish when close to the mucosal surface

7. Odontogenic cysts : Derived from rests of Malassez .
1 Periapical radicular cyst : is an odontogenic cyst derived from rest of Malassez that proliferated due to inflammation . It could be located laterally & thus called lateral cyst.
2 Residual cyst .

8. Derived from reduced enamel epithelium .
1 . Dentigerous cyst : is the most common odontogenic cyst (20-24 % of all epi. Lined jaw cysts) that surrounds the crown of an impacted tooth thus the arch will have at least one missing tooth. It is caused by fluid accumulation between reduced enamel epithelium & the enamel surface resulting in a cyst which the crown is located within the lumen & root (or roots ) outside.

10. Dentigerous cyst

11. Histopathology :
Lining: non keratinized stratified squamous epi 2-10 cells in thickness.
Sometimes becomes inflamed (chronic or acute) changing the lining to hyperplastic or atrophic or ulcerated.
Other microscopic features include :-
1.Cholesterol deposits.
2.Hemosidrein deposits.
3.Hylaline (rushton) bodies.
4.Lipid laden macrophages.
5.Mucus cells
Long standing dentigerous c. will occasionally exhibit areas of keratinization or premalignant (dysplastic ) changes.

12. Pathogenesis ;unknown , but it has been suggested that periapical inflammation from a deciduous tooth may stimulate follicular tissue of the corresponding unerupted permanent tooth to detach & undergo cystic change.
Teeth involved : 3rd molars , max. permanent canines , & in rare instances unerupted decidous teeth .

13. May also involve unerupted supranumerary teeth & odontomas.
Most often detected in teenagers & young adults .
May display considerable growth potential leading to destruction of medullary bone & expansion of the jaw .

14. Treatment
Encleation ( if the tooth is a molar ; extraction with encleation ) . if the tooth is the maxillary canine the cyst may be excised or marsupialized & tooth brought in proper alignment by orthodontic treatment.
Recurrence is uncommon.
Sometimes different epithelial neoplasms can arise :
1.Ameloblatoma.
2.Mucoepidermoid carcinoma .
3.squamous cell carcinoma .

15. 2 . Eruption cyst :
Is an odontogenic cyst with the histologic features of a dentigerous cyst that surrounds a tooth's crown that has erupted through bone but not the soft tissue . It forms from the accumulation of fluid or blood in the dilated follicle & is clinically visible as a soft fluctuant mass on the alveolar ridge if it contains blood it may have a blue or purplish color.
No treatment is required as it ruptures spontaneously .

16. Eruption cyst

17. 3. Paradental cyst :
Is a cyst of odontogenic origin commonly located subgingivally on the buccal aspect of an erupted mandibular molar (bifurcation cyst ) or the distal surface of a partially erupted mandibular third molar .

18. pathogenesis
The first theory claims that the predisposing factor is that the crown exhibits an anomaly called cervical enamel projection . When inflammation is associated with the cyst formation in a superficial intraosseous location in young patients this may induce reactive periosteal proliferation or localized form of Garrres osteomylitis that resolves when the cyst is removed.

19. The second theory claims that the rests are stimulated around the furcation area because the tooth fails to quickly attain a state of full eruption so the margin of free gingival above the height of contour on the buccal surface of the crown , will allow for continuous impaction of food particles & bacteria into the sulcus resulting in an inflamed deep pocket or paradental cyst that eventually extends to the bifurcation area.

20. Histopathology
Lining :hyperplastic layer of non keratinized squamous epi. Infiltrated by neutrophils.
Capsule is chronically inflamed.

21. Derived from dental lamina .
1. Odontogenic keratocyst : is a cyst derived from the remnant of dental lamina with a biologic behavior similar to a benign neoplasm , with a distinctive lining of cells in thickness & that exhibits a basal cell layer of palisaded cells & a surface of corrugated parakeratin .

22. 2/3 of all cases are found in the mandible
2/3 of all cases are found in the mandible . ( mainly posterior & ramus area ) .
3-12% of all odontogenic cysts.
Grows in an anterioposterior direction & may reach a large size without clinical expansion of the jaw .
Multilocular .
If multiple in all 4 quadrants it is called Garlin Goltz syndrome.
Sometimes it could develop around crown of an unerupted tooth giving an appearance similar to dentigerous cyst .
Has a remarkable growth potential & can grow to large sizes with massive bone destruction.
Peak incidences during 2nd – 3rd decades of life.
Recurrence rate 25% -60% ( like ameloblastoma ).

23. Radiographic features : well defined solitary lesion , smooth or scalloped margins , multilocular , polycystic , radiolucency with thin corticated margin.In % maybe associated with crown of unerupted tooth. In edentulous area cannot be differentiated from residual cyst .It could occur between teeth (like lat. Pd cyst ) or in the midline of the max mimicking nosopalatine duct cyst .
Orthokeratinized odontogenic cyst is not considered as a keratocyst because it has different histopathological & clinical features (forms a distinctive layer of orthokeratin).It occurs in posterior mandible (75%with unerupted 3rd molar )in the 2nd & 3rd decade of life with a male predilection . Recurrence rate 2%

24. Odontogenic keratocyst

25. Orothokeratinized odontogenic cyst

27. Treatment :
Enuclation or marsupialization ( to reduce the size before complete surgical removal ).
Recurrence is expected (5-10 years after surgey).

28. Gorlin-Goltz syndrome is heritable as an autosomal dominant trait
Gorlin-Goltz syndrome is heritable as an autosomal dominant trait. It consists essentially of the triad of multiple basal cell naevi, keratocysts of the jaws and skeletal anomalies. Key features of Gorlin-Goltz syndrome • Characteristic face with frontal and parietal bossing and broad nasal root. • Multiple keratocysts of the jaws. • Multiple, naevoid basal cell carcinomas of the skin • Skeletal anomalies (usually of a minor nature) such as bifid ribs and abnormalities of the vertebrae • Intracranial anomalies may include calcification of the falx cerebri and abnormally shaped sella turcica • Cleft lip and palate in approximately 5%

30. 2. lateral periodontal cyst :
Is a slowly growing non- expansile developmental odontogenic cyst derived from one or more rests of the dental lamina , exhibiting a lining of 1-3 cuboidal cells& distinctive focal thickenings.
Radiographically it appears as a well defined , unilocular radiolucency between the roots of vital teeth .(less than 1cm in diameter ).
Most common in mandibular premolar region & in anterior maxilla between the canine & lateral incisor .
Age group : approximately 50 years.

31. Histopathology :
Thin lining of non keratinized epi. (1-3 cells) with glycogen rich clear cells .
Wall contains rests of serres.

32. Treatment :
Enucleation , recurrency uncommon.

33. 3. Gingival cyst of adults
is a small developmental odontogenic cyst of the gingival soft tissue derived from the rests of dental lamina.
The gingival cyst of adults is the counterpart of the lateral periodontal cyst the difference between them is that the gingival cyst is outside the bone (extraosseous ) while the lateral is inside the bone (intraosseous ) .
Clinically it occurs as a firm but pressible fluid filled swelling on the mandibular or maxillary facial gingiva in the premolar cuspid & incisor region.

34. Histopathology :
-Lining (like L. Pd. Cyst ) thin (2-5 cells ) thickness.
-Clear cells are present .
Treatment:
Enucleation , no recurrency.

35. Gingival cyst of the adult

36. 4. Gingival cyst of newborn (Epstein pearls) are small white or yellow cystic vesicles (1 to 3 mm in size) often seen in the median palatal raphe of the mouth of newborn infants (occur in 65-85% of newborns). They are filled with fluid They are caused by entrapped epithelium during the development of the palate. They do not require treatment because they resolve spontaneously over the first few weeks of life.

37. 5. Glandular odontogenic cyst :
is a unilocular or multilocular odontogenic cyst derived from the rests of dental lamina (includes mucus cells ) .
It is similar to polycystic lateral p.d. cyst but has a much greater growth potential & propensity to recur.
Radiographically is not specific but commonly large well defined uni or multilocular radiolucency . ( primarally in the mandible ).
Treatment:
Enucleation with curettage.

38. Glandular odontogenic cyst : (sialo-odontogenic cyst ).
A unilocular or multilocular odontogenic cyst derived from the rests of dental lamina & characterized by a lining of various numbers of small intra epithelial glandular structures lined by cuboidal or columnar cells often including mucus cells.

39. * Histological features resemble the polycystic variant of lateral Pd cyst .
Thin sq. epi. Lining with focal thickenings(plaques).
Small glandular structures or microcysts( within the lining )with a lining of single layer of columnar or cuboidal cells.
the glandular spaces contian secretory products.
It has a greater growth potential .
It has propensity to recur.
Treatment : enucleation & curettage.

40. Non odontogenic cyst
1.Nasopalatine duct cyst The nasopalatine duct connects the organ of Jacobson in the nasal septum to the palate in many animals. Jacobson's organ is joined centrally to an accessory olfactory bulb. Cats, for instance,may sometimes be noticed to sense an interesting odour by inhaling through the mouth, and in most species Jacobson's organ is used to assess the state of sexual readiness of potential mates. Jacobson's organ has disappeared in the human, and only a few epithelial cells lying along the line of the nasopalatine duct, persist. These cells can give rise to nasopalatine duct cysts. Nasopalatine cysts, which form in the midline of the anterior maxilla, are uncommon. The nasopalatine, incisive canal, median palatine and median alveolar cysts are variants of the same lesion, varying slightly in position in relation to the postulated line of the incisive canal.

41. 2.Nasolabial cyst This very uncommon cyst forms outside the bone in the soft tissues, deep to the nasolabial fold. It probably arises from remnants of the nasolabial duct and is occasionally bilateral. The lining is pseudo-stratified columnar epithelium with or without some stratified columnar epithelium. If allowed to grow sufficiently large, the cyst produces a swelling of the upper lip and distorts the nostril. Treatment is usually by simple excision but occasionally may be complicated if the cyst has perforated the nasal mucosa and discharged into the nose.

42. Thyroglossal tract cyst.
A cyst located above the thyroid gland & beneath the base of the tongue with a lumen lined by a mixture of epi. cell types derived from remnants of of the embryonic thyroglossal tract & often containing thyroid tissue in the capsule .
Appears in MRI & CT scan investigations .
The patient has dysphagia.
In aspiration a hormonal fluid will be detected.
Treatment: Complete surgical excision because recurrence is possible .

43. Cysts of embryonic skin :
1. dermoid cyst : cyst of the midline of upper neck or the anterior floor of the mouth of young patients with one or more skin appendages (hair , sweat or sebaceous gland ).
Could be below or above mylohyiod muscle .
2. epidermoid cyst : cyst of skin filled with keratin no skin appendages in the capsule wall .
Treatment : surgical excision.