Cysts of the Oral and Paraoral Regions

Cysts of the Oral and Paraoral Regions

• Definition: A cyst is a pathological cavity lined by epithelium, containing fluid or semi-fluid material. Pseudocysts are cysts not lined by epithelium.
• Classification: Odontogenic or Non-Odontogenic cysts.
  • Odontogenic Cysts: Arise from odontogenic epithelial cells.
    • Periodontal Cysts:
      • Inflammatory: 1) apical, 2) lateral, 3) residual
      • Developmental: 1) lateral developmental, 2) gingival cyst of adults, 3) gingival cyst of newborn (Bohn's nodules)
    • Dentigerous Cyst: (Central, lateral, circumferential)
    • Primordial Cyst, Odontogenic Keratocyst.
  • Non-Odontogenic Cysts:
    • Nasopalatine Cysts: 1) Incisive Canal Cyst, 2) Cyst of palatine papilla
    • Fissural Cysts: 1) Globulomaxillary, 2) Nasolabial, 3) Median (maxilla: median palatal, mandible: median mandibular)
    • Pseudocysts: 1) Traumatic bone cyst, 2) Aneurysmal bone cyst, 3) Static bone cyst
    • Soft tissue cysts of the jaw and neck: 1) Dermoid and epidermoid cysts, 2) Thyroglossal tract cyst, 3) Benign lymphoepithelial cyst (branchial-cleft cyst), 4) Mucous retention and mucous extravasation cysts

Epithelium and Odontogenic Cysts

• Origin of epithelium: Epithelium associated with odontogenic cysts originates from enamel organ, reduced enamel epithelium, epithelial rests of Malassez, and epithelial rests of Serres.
  • Periodontal Cysts: 65% of all cysts, result from inflammatory hyperplasia of epithelial rests of Malassez in periodontal ligament.
  • Periapical Cysts: Develop from periapical granulomas due to inflammatory hyperplasia within the granuloma. Cells in the central portion can be separated from nutrients within capillaries, resulting in necrosis and liquefaction.

Mechanism of Enlargement

• Breakdown of complex proteins: Remnants of cellular debris break down complex tissue proteins into simpler molecules, increasing the osmotic pressure of cystic fluid.
• Fluid transport: Resulting in fluid transport across the semipermeable epithelial lining into the lumen, leading to cyst enlargement.

Clinical Features (Apical Periodontal Cysts)

• Age: Adult (third to sixth decades), more common in men
• Site: Maxilla, especially the anterior region
• Symptoms: Usually asymptomatic, discovered during routine x-ray. Slowly progressive painless swelling, painful swelling if infected. Swelling hard at first, eggshell crackling of bone later.
• Radiographic Findings: Well-defined unilocular radiolucency, thin opaque margin, varying dimeter from 5 mm to several centimeters. May show infection which causes outline to be hazy, small radicular cyst and periapical granuloma may appear radiographically similar.

Microscopic Variations in Cyst Walls

• Epithelial Lining: Can include stratified squamous epithelium, respiratory or pseudostratified ciliated columnar epithelium (maxillary sinus cysts), or embryonic epithelium.

Cyst Wall Connective Tissue

• Composition: Contains collagen fibers, fibroblasts, capillaries, inflammatory cells (acute and chronic), foci of dystrophic calcification as haematoxylin masses, cholesterol clefts, Degenerated plasma cells (Russel bodies), eosinophilic Hyaline bodies or Rushton bodies.

Cyst contents and differential diagnosis

• Cyst fluid: Contains serum albumin, globulin, cholesterol, and nucleoproteins.
  • Infected: May be purulent
• Differential Diagnoses: 1) Periapical granuloma, 2)Periapical scar, 3) Early phase of periapical cemental dysplasia

Cysts of the Palatine Papilla and Fissural Cysts

• Etiology and Pathogenesis: Develop from dental lamina remnants in soft tissue between oral epithelium and periosteum.
• Clinical appearance: Soft, painless swelling less than 1 cm in diameter, same color as adjacent normal mucosa.
• Radiographic features: Dental x-ray film is negative.
• Histopathologic features: Thin, flattened squamous epithelial lining.

Gingival Cyst of Newborn (Bohn's Nodules)

• Multiple small white nodules: On alveolar ridge, less than a few mm, asymptomatic.
• Origin: Remnants of dental lamina, forming small keratinized cysts.
• Spontaneous resolution: Ruptures and resolves spontaneously in most cases.

Dentigerous Cysts (Follicular Cysts)

• Definition/Characteristics: Contains unerupted tooth, attached to the neck of the tooth (15-17% of all jaw cysts)
• Etiology and Pathogenesis: Cystic change from reduced enamel epithelium, after complete enamel formation, in the space between reduced enamel epithelium and the tooth crown.
• Clinical Features: No symptoms in small cysts, possible pain and infection in larger cysts
• Radiographic Features: Well-defined unilateral radiolucency associated with the crown of an unerupted tooth; may be surrounded by a thin sclerotic layer.
• Histopathologic Features: Lined by a thin, regular, non-keratinized, stratified squamous epithelium, Inflammatory cells are absent in the connective tissue wall, Cholesterol clefts and foreign body giant cells may also be present.

Other Cysts (Incisive Canal Cyst, Nasopalatine Cyst, etc)

• Etiology: Originates from the remainder of epithelium tissue remnants from the embryonic nasopalatine ducts that are present inside Nasopalatine canal,
• Clinical Features: Asymptomatic, discovered in routine x-ray. Pain, salty taste, numbness of anterior palate, and swelling if infected.
• Radiographic Features: Round/ovoid well-defined radiolucency in midline between the roots of the maxillary central incisors. May not exceed 6mm in diameter
• Histopathologic Features: Pseudostratified ciliated columnar epithelium in some cases, stratified squamous epithelium, and combinations. The connective tissue wall shows signs of inflammation.

Eruption Cysts

• Description: Uncommon superficial dentigerous cyst occurring in the soft tissue of the gum or alveolar mucosa over an erupting tooth.
• Clinical Features: Soft, rounded swelling, same color as adjacent normal mucosa; possibly filled with blood ("eruption hematoma").
• Treatment: No treatment needed; typically disappears spontaneously.

Odontogenic Keratocyst (Primordial Cyst)

• Least Common: 7% of odontogenic cysts
• Age: 2nd and 3rd decades
• Location: Usually in the mandible, followed by maxilla
• Symptoms: Asymptomatic unless infected
• Radiographic Features: Unilocular radiolucency, smooth margins; seldom larger than 1 cm in diameter, but may be larger in infected cases.
• Histopathologic Features: Thin, regular, stratified squamous epithelium; parakeratosis (high recurrence rate) or orthokeratosis (lower recurrence rate)

Benign Cervical Lymphoepithelial Cyst

• Location: Lateral neck, anterior to sternomastoid muscle.
• Origin: Remnants of epithelial cells of branchial grooves, entrapped in cervical lymph nodes
• Symptoms: Asymptomatic; movable mass
• Histopathology: Lined by stratified squamous epithelium (sometimes pseudostratified columnar epithelium), with lymphoid follicles.

Mucous Extravasation Cyst

• Etiology and Pathogenesis: Mechanical trauma to minor salivary gland excretory duct, resulting in extravasated mucous inducing inflammatory reaction in connective tissue surrounding.
• Clinical Features: Painless swelling, smooth surface, translucent; varies from mm to cm in size
• Site: Lower lip, buccal mucosa, ventral surface of the tongue, floor of the mouth (Ranula).
• Histopathology: Mucous pool surrounded by fibrous/granulation tissue, with neutrophils, macrophages, lymphocytes, and possibly plasma cells.
• Treatment: Surgical excision

Other Cysts (Aneurysmal Bone Cysts, Static Bone Cysts)

• These descriptions are incomplete in the provided context and require further information from the original texts.