The 'ring and arc' calcification pattern on plain radiograph or CT within a bone lesion is characteristic of which tissue type?

• A Osteoid matrix (osteosarcoma)
• B Fibrous tissue (fibrous dysplasia)
• C Haemorrhagic tissue (aneurysmal bone cyst)
• D Chondroid matrix (enchondroma or chondrosarcoma) ✓

Explanation

Ring and arc (also called rings-and-arcs or lobulated) calcification represents mineralisation of the periphery of chondroid lobules and is pathognomonic of cartilaginous tumours — enchondroma, chondrosarcoma, and periosteal chondroma. Osteoid matrix produces dense, cloud-like or ivory (fluffy) calcification. Fibrous dysplasia shows a 'ground-glass' matrix. Aneurysmal bone cysts are predominantly lytic without this specific calcification type.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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