Are expansile bone lesions helpful in differentiating benign from aggressive disease?

• A. No; they range from aneurysmal bone cysts to malignant neoplasia, therefore of low utility
• B. Yes; they are highly diagnostic
• C. They indicate infection
• D. They are only seen in benign lesions

Answer: (A)

Expansile growth is a non-specific pattern. It describes bone that expands and thins the cortex, but this outward remodeling can occur in a wide range of conditions—from benign lesions like aneurysmal bone cysts or fibrous dysplasia to malignant processes such as osteosarcoma or metastasis. Because both benign and malignant disorders can be expansile, this feature provides little reliable information about whether the disease is aggressive. More telling clues come from other imaging signs (cortical destruction, soft tissue mass, permeative or moth-eaten lysis, and aggressive periosteal reactions) and, when needed, biopsy for definitive diagnosis. Hence expansile lesions have low utility for differentiating benign from aggressive disease.