Pathology · patient case question
What is the most likely diagnosis?
Patient case: Fine straight septa in the posterior mandible
Patient: Female, 28 years old
Chief Complaint: “This side of my jaw has slowly got bigger over the last year.”
Background: Healthy, no medications. Painless throughout.
Vital Signs: BP 116/72 mmHg · HR 70 bpm
Findings: Painless buccolingual expansion of the posterior left mandible. The panoramic radiograph shows a multilocular radiolucency whose internal septa are FINE, STRAIGHT and set at angles to one another. The adjacent teeth are DISPLACED but their roots are NOT resorbed. All teeth in the region are vital.
Show answer and explanation
Correct answer: D. Odontogenic myxoma
- A. The odontogenic keratocyst characteristically grows ANTEROPOSTERIORLY through the marrow spaces with minimal buccolingual expansion, and shows a thin corticated, often scalloped border. Marked expansion argues against it.
- B. Ameloblastoma is the main differential, but its septa are COARSE and CURVED, producing the soap-bubble or honeycomb pattern, and it characteristically RESORBS the roots of adjacent teeth with a knife-edge appearance. This lesion displaces rather than resorbs.
- C. Central giant cell granuloma favours the ANTERIOR mandible in patients under 30 and characteristically CROSSES THE MIDLINE, with wispy, ill-defined granular septa. It is histologically identical to a brown tumour, so parathyroid function must be checked before accepting the diagnosis.
- D. CORRECT. The ODONTOGENIC MYXOMA is defined radiographically by septa that are FINE, STRAIGHT and set at angles to each other, giving the TENNIS RACQUET or STEP-LADDER appearance. It arises from dental papilla mesenchyme, favours the posterior mandible in the second to fourth decades, and characteristically DISPLACES teeth and grows between them rather than resorbing them. Because it is gelatinous, unencapsulated and infiltrates marrow spaces, it recurs after simple curettage — resection with margins is usually required.
Note: For any MULTILOCULAR radiolucency of the posterior mandible, read the SEPTA and read what happens to the ROOTS. Coarse curved septa with root resorption → ameloblastoma. Fine straight angular septa with tooth displacement → myxoma. Minimal expansion with anteroposterior growth → OKC. Anterior, crossing the midline, under 30 → central giant cell granuloma. Also keep the vascular lesions in mind, since biopsying an arteriovenous malformation is catastrophic.