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Dx: Odontogenic Myxoma KEY FACTS Terminology Definition : Benign tumor of odontogenic ectomesenchyme Imaging Mandible > maxilla; premolar-molar regions Unilocular or multilocular radiolucency with thin, straight internal septa Septa may form right angles or geometric shapes In larger lesions, septa may be coarse, curved ( soap bubble ) and mimic ameloblastoma Borders may be well defined or ill defined; if well defined, often lobular or scalloped Top Differential Diagnoses Ameloblastoma Central giant cell granuloma Aneurysmal bone cyst Central hemangioma Osteosarcoma Clinical Issues Uncommon ; only 3-6% of odontogenic tumors Wide age range; average 25-30 years No gender predilection May demonstrate rapid growth and expansion Infiltrates surrounding bone; does not metastasize Treatment: Curettage for small lesions Extensive resection for large lesions Complete removal difficult with 25% recurrence rate : Follow-up required for at least 5 years Diagnostic Checklist Look for thin cortical margin to rule out osteosarcoma when pseudoperiosteal reaction present TERMINOLOGY Synonyms Myxoma, myxofibroma, fibromyxoma Definitions Benign tumor of odontogenic ectomesenchyme IMAGING General Features Best diagnostic clue: Multilocular radiolucency with thin, often straight, internal septa at right angles Location Any area of jaws; mandible > maxilla (3:1) Most common in premolar-molar regions Size: Variable, depending on when discovered Imaging Recommendations Best imaging tool: CT or CBCT: Evaluation of extent & margins Radiographic Findings Radiography Small lesion may be unilocular and well defined Larger lesion may be well defined or ill defined Lobular or scalloped edges ± cortication Internal septa often thin: May form right angles with each other or make geometric shapes May be coarse and curved ( soap bubble ) and mimic ameloblastoma May extend at periphery in radiating pattern giving pseudoperiosteal reaction If large, may displace teeth; tooth resorption rare CT Findings CBCT or bone CT Better determines extent of larger lesions Thin cortical margin helps differentiate from osteosarcoma when pseudoperiosteal reactions are present MR Findings T2WI: ↑ signal: Establishes tumor extent DIFFERENTIAL DIAGNOSIS Ameloblastoma Multilocular radiolucency, corticated border, and coarse, curved internal septa ( soap bubble ) Most common in posterior mandible May displace, resorb teeth Central Giant Cell Granuloma Multilocular radiolucency; well defined, noncorticated Wispy septa, some at right angles to periphery Painless, expansile; may displace, resorb teeth Anterior mandible most common; may cross midline Aneurysmal Bone Cyst Multilocular radiolucency with well-defined borders that are curved or hydraulic Internal septa wispy, ill defined, some at right angles to periphery Rapid expansion in posterior mandible typical Fluid-fluid levels on T2WI MR Central Hemangioma Multilocular radiolucency: Corticated or ill defined May see small compartments internally, similar to large marrow spaces surrounded by coarse trabeculae Slow enlargement of jaw, may or may not be painful May produce linear spicules ( sun ray ) at periphery Osteosarcoma Spiculated periosteal reaction ( sun ray ); cortex not intact PATHOLOGY Gross Pathologic & Surgical Features Not encapsulated Loose gelatinous consistency ; pathognomonic Microscopic Features Resembles developing tooth mesenchyme (dental papilla) Stellate, spindle-shaped, or round cells in abundant loose myxoid stroma May see small islands of epithelium CLINICAL ISSUES Presentation Most common signs/symptoms May expand bone Slow growing, painless Demographics Age: Wide range; average: 25-30 years Gender: No gender predilection Epidemiology: Uncommon; only 3-6% of odontogenic tumors Natural History & Prognosis Infiltrates surrounding bone but does not metastasize May demonstrate rapid growth and expansion Treatment Curettage for small lesions Extensive resection for large lesions Follow-up required for at least 5 years; complete removal difficult with 25% recurrence rate DIAGNOSTIC CHECKLIST Image Interpretation Pearls Look for thin cortical margin to rule out osteosarcoma when pseudoperiosteal reaction present
