Fig. 6

Crystal Deposits. a Calcium pyrophosphate (CPP). Synovial sclerosis with large amount of CPP (× 100), CPP positive birefringent crystals with rhomboid shape under polarized light, inset (× 200). b Monosodium urate. Macrophage and giant cell reaction to fascicles of dissolved urate crystals (black arrow) (H&E × 200), residual negative birefringent crystals under polarized light in inset (× 400). c Oxalate. Deposition of oxalate crystals in bone marrow in a case of primary oxaluria (H&E × 200). Positive birefringent crystals under polarized light in inset (× 400). d Cholesterol. Clefts of cholesterol crystals in long-standing chronic bursitis with macrophage reaction with numerous foamy forms to particulate wear debris of MoM THA implant (H&E × 200). e Hydroxyapatite (calcinosis). Spherical and targetoid deposits of calcium hydroxyapatite in calcific bursitis of shoulder joint (H&E × 200). f Hydroxyapatite (calcinosis). Bone marrow stromal reaction to deposits of calcium hydroxyapatite (black arrow) with brisk osteoblatic activity and thick osteoid seam (white arrow) in a femoral head with periarticular tumoral calcinosis in a case of long-standing scleroderma. Undecalcified bone section (Goldner’s Masson Trichrome × 200) with black calcium hydroxyapatite deposits evident in inset (blue arrow) (Von Kossa × 200)