Expansile solid lesion of the subarticular distal radius destroying cortex, which measures 2.9 x 2.7 x 3.8 cm (AP x ML x CC). Signal characteristics are low T1, high T2 and homogeneous enhancement. Narrow zone of transition to normal marrow proximally. Tumour destroys cortex on the dorsal surface. Abnormal enhancing tissue within the extensor tendon sheaths in continuity with the solid mass. Tumour also destroys cortex on the volar aspect but is contained by pronator quadratus. Flexor tendons and carpal tunnel contents appears normal. Buckling of the cortex medially and laterally in keeping with pathological fracture and associated soft tissue oedema. Conclusion: Distal radius lesion most in keeping with giant cell tumour with evidence of local extension into the extensor compartment.