A biopsy of bone shows prominent cement lines, irregular woven bone replacing lamellar bone, and mosaic pattern on H&E. Which histological finding is characteristic of Paget's disease of bone?

• A Bone marrow replaced by adipocytes with empty lacunae (osteocyte death)
• B Woven bone with abundant osteoclasts in giant cell tumour-like pattern
• C Prominent basophilic cement lines creating a 'mosaic' or 'jigsaw puzzle' pattern due to repeated cycles of resorption and deposition ✓
• D Lamellar bone with concentric osteons (haversian systems) and periosteal new bone only

Explanation

Paget's disease (osteitis deformans) is characterised on histology by a mosaic or 'jigsaw puzzle' pattern: numerous prominent, irregular, deeply staining basophilic cement lines (reversal lines) that demarcate areas of previously resorbed bone refilled with new bone. Each cycle of resorption (osteoclastic phase) followed by rapid, disorganised deposition (osteoblastic phase) creates an additional cement line. Over time, the cortical bone is replaced by coarse-fibered woven bone with thickened trabeculae and a mosaic appearance. Empty lacunae (osteocyte death) with fatty marrow is characteristic of avascular necrosis. Giant cell tumour histology is distinct.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.