A panoramic radiograph shows a well-defined radiolucency in the mandibular ramus. Each of the following belongs in the differential diagnosis EXCEPT:

Correct answer: A. A periapical (dentoalveolar) abscess

• A. CORRECT — this is the EXCEPTION. A periapical ABSCESS is by definition ODONTOGENIC — it arises from a necrotic pulp and is anatomically tied to a tooth apex. The ramus is EDENTULOUS bone with no tooth apices, so a periapical abscess cannot originate there.
• B. A Stafne defect (static bone cavity / lingual salivary gland depression) is a well-corticated radiolucency, classically below the inferior alveolar canal near the angle — a normal anatomic variant containing salivary or fatty tissue that requires no treatment.
• C. A traumatic (simple) bone cyst can occur in the ramus, classically as a well-defined radiolucency; in the tooth-bearing region it scallops between roots.
• D. Osteomyelitis CAN involve the ramus, producing an ill-defined moth-eaten radiolucency, sometimes with sequestra and periosteal new bone.

Note: Ramus radiolucency differential also includes: keratocyst, ameloblastoma, central giant cell lesion, and vascular malformation.