Non-epithelial cysts (not true cysts)

Solitary bone cyst

Radiology

The solitary bone cyst appears as a well-defined but non-corticated radiolucency. Typically, it has little effect
on adjacent structures and 'arches' up between the roots of teeth .

The inferior dental canal may not be displaced, but the cortical margins of the canal may be lost where it overlies the lesion. Expansion is rare.

Pathology

The cyst is lined by fibrovascular tissue that often includes haemosiderin and multinucleate giant cells.

Aneurysmal bone cyst

Radiology

The aneurysmal bone cyst typically presents as a fairly well-defined radiolucency. Sometimes it has a multilocular appearance because of the occurrence of internal bony septa and opacification. Marked expansion is a feature.

Pathology

The predominant feature of an aneurysmal bone cyst is the presence of blood-filled spaces of variable size lying in a stroma rich in fibroblasts, multinucleate giant cells and haemosiderin. Deposits of osteoid are also seen
 

• SLE → IgG, IgM, IgA deposits at BMZ + superficial lamina propria
• Lichen Planus (Erosive/Atrophic) → Autoimmune T-cell; BMZ involvement
• Cicatricial Pemphigoid → Subepidermal blistering from anti-BMZ antibodies

• Actinomycosis (Sulfur Granules):

  • Yellow sulfur granules: Are actually bacterial colonies.

  • Histopathology: Colonies appear "cotton wool" shaped. (Note: "Cotton wool appearance" is seen radiographically in Paget's disease).

• Tuberculosis (TB):

  • Diagnosis (Gold Standard): Presence of acid-fast bacilli in sputum.

  • Staining Method: Ziehl-Neelsen staining method is used to identify acid-fast bacilli.

  • Scrofula: TB of cervical lymph nodes.

  • Lupus Vulgaris: TB of skin.

• Tongue & Gingival Appearance in Systemic Conditions:

  • Strawberry tongue and Raspberry tongue: Seen in stomatitis of Scarlet Fever.

  • Strawberry Gingivitis: Seen in Wegener's Granulomatosis.

• Dentigerous Cyst (Follicular Cyst):

  • Most common Developmental Odontogenic Cyst.

  • Always associated with the crown of an unerupted/impacted tooth.

  • Derived from Reduced Enamel Epithelium (REE).

  • Differential diagnosis: Eruption cyst, Paradental cyst (also from REE).

• Nasopalatine Duct Cyst (Incisive Canal Cyst/Median Anterior Maxillary Cyst - MAMC):

  • Most common Developmental Non-odontogenic Cyst.

  • Located in the midline of the anterior maxilla.

• Radicular Cyst (Periapical Cyst):

  • Most common Odontogenic Cyst overall.

  • Always associated with a non-vital tooth.

  • Inflammatory origin.

• Odontogenic Keratocyst (OKC) / Keratocystic Odontogenic Tumor (KCOT):

  • Primordial Cyst: An OKC found in place of a missing tooth.

  • Protein Content: Less than 4 gm/dL.

  • Aggressive Behavior: High mitotic activity, high PCNA index, and Ki67 activity.

  • Derived from Rests of Serres (remnants of dental lamina).

• Mucocele:

  • Common term for:

    • Mucous Extravasation Phenomenon (Pseudocyst): No epithelial lining.

    • Mucous Retention Cyst (True Cyst): Has an epithelial lining.

• Class III (Underdeveloped Maxilla) → Cleidocranial dysplasia, Craniofacial dysostosis, Achondroplasia, Down syndrome, Osteogenesis imperfecta
• Class II (Underdeveloped Mandible) → Treacher Collins syndrome, Pierre Robin syndrome
• Both Jaw Underdevelopment → Hypopituitarism
• Maxillary Enlargement → Metastatic fibrous dysplasia
• Mandibular Enlargement → Acromegaly
• Bimaxillary Enlargement → Paget’s Disease
• Mandibular Asymmetry → Caffey’s Disease
• Prominent Premaxilla → Thalassemia
• Underdeveloped Premaxilla → Congenital Syphilis

• Epithelial Plaques (localized thickenings): Found in:

  • Lateral Periodontal Cyst

  • Botryoid Odontogenic Cyst

  • Gingival Cyst of Adults

  • Glandular Odontogenic Cyst