Odontogenic Cysts

Inflammatory:

Periapical cyst (Radicular cyst): When the pulp of the tooth undergoes necrosis due to caries or trauma a granulation tissue response known as a peri-apical granuloma may develop. This can stimulate proliferation of epithelium (Malassez rests) near the tooth to proliferate and become cystic forming a periapical cyst. Ocassionally the epithelium will contain linear and hairpin-shaped hyaline bodies known as Rushton bodies.

Developmental:

Dentigerous cyst: Before tooth formation if fluid accumulates between reduced enamel epithelium (dental follicle epithelium) and the crown of the tooth. Varible histo appearances. Cyst lined by a thin flattened non keratinising epithelium. Loose connective tissue stroma with scattered odontogenic epithelial rests. These may undergo dystrophic calcification.

Keratocystic Odontogenic Tumour/Odontogenic keratocyst: Higher rate of recurrence. Assoc with nevoid basal cell carcinoma syndrome (Gorlin’s syndrome). Cyst lined by stratified squamous epithelium of uniform thickness wtih desquamated keratin within the cyst lumen. Epithelial lining shows a palisaded cuboidal to columnar basal layer and a corrugated parakeratinising surface. No granular cell layer.

Orthokeratinising Odontogenic cyst: (Important to differentiate from KOT) Cyst lined by stratified squamous epithelium with orthokeratosis. Granular cell layer present. No palisaded columnar basal layer or corrugated/wavy layer of keratin.

Gingival (alveolar) cyst of the newborn: Common, multiple small pearl like nodules on the alveolar ridge. Stratified squamous lining with desquamated parakeratin in lumen. (From remnants of dental lamina epithelium)

Gingival cyst of the adult: Uncommon. Cyst with a thin attenuated lining. (From remnants of dental lamina epithelium).

Lateral periodontal cyst (Botryoid Odontogenic cyst): Lined by a thin layer of epithelium with focal nodular thickening. Radiologically presents as a well circumscribed, unilocular radiolucency located lateral to the roots of vital teeth.

Calcifying odontogenic (Gorlin) cyst/ Calcifying cystic odontogenic tumour: Given apparent neoplastic potential discussed under tumours in text. Aka Dentinogenic ghost cell tumour (in WHO text). Well defined unilocular radiolucency with scattered radioopacities. Proliferation of odontogenic epithelial cells associated with the cystic lumen. Palisaded basal cell layer of the lesional epithelium and the ghost cell change with areas of dystrophic calcification.

Glandular odontogenic cyst: Stratified squamous epithelial lining that exhibits ciliated columnar cells on the surface. The epithelium contains prominent gland like spaces that are also lined by columnar cells.

Eruption cyst: Fluid/haemorrhage between dental follicle and crown assoc with a erupting tooth. Esp in children.

Carcinoma arising in odontogenic cysts

References:

Gnepp. Diagnostic Surgical Pathology of the Head and Neck.

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