General Information

• Primary intraosseous epithelial neoplasm
• Low-grade malignancy and predilection for tibia
• Associated with intraosseous fibro-osseous proliferation (osteofibrous dysplasia)
• Classic vs. Differentiated
• Classic – grow beyond cortex, older patients, sometimes metastasize
• Differentiated – confined to cortex, earlier age, do not metastasize

Clinical Presentation

Signs/Symptoms:

• pain & Swelling, painless swelling, or pain alone
• 50% have history of localized trauma

Prevalence:

• males and females affected equally

Age:

• range 3-72 years old
• ~50% present in second or third decade

Sites:

• Predilection for tibia (90%)
• favoring diaphyseal portion of bone

Radiographic Presentation

• Sharply defined osteolytic defect (lobulated, multicystic, or “soap bubble”)
• May be considerable perilesional sclerosis

Roll over the images for more information

Gross Pathology

• Sharp demarcation and lobulated configuration may be seen
• Solid areas are soft to firm, gray or white, granular or fibrous
• Cystic spaces and areas of intralesional hemorrhage are common
• Length: 5 cm to entire shaft

Microscopic Pathology

• Four histologic patterns:
• spindled
• basaloid
• tubular
• squamoid
• Situated in a loose or dense fibrous stroma
• May form tubular structures lined by one or two cells, which may branch and anastomose
• Appear as small, vascular tubules with lumens in cross section
• May have squamous differentiation
• Nuclei are usually bland

Roll over the images for more information