A 45-year-old woman has a centrally located calcified lesion in the distal femur. CT shows a cartilaginous matrix with ring and arc calcification and endosteal scalloping exceeding two-thirds of the cortical thickness, with mild associated pain. Which finding BEST supports chondrosarcoma over a benign enchondroma?

• A Ring and arc pattern of matrix calcification
• B Endosteal scalloping greater than two-thirds of cortical thickness ✓
• C Central location within the medullary cavity
• D Occurrence in the long bones of an adult

Explanation

Deep endosteal scalloping beyond two-thirds of cortical thickness, cortical destruction, periosteal reaction, soft tissue mass, and pain favor chondrosarcoma over enchondroma. Ring and arc calcification merely identifies a cartilaginous matrix and is seen in both benign and malignant cartilage tumors. Central medullary location in adult long bones is typical of enchondroma, so it argues against malignancy rather than for it.

Reference: Radiology Review Manual, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.