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Pseudotumours are well recognised as a complication of metal-on-metal hip arthroplasties and are thought to develop on the basis of an innate and adaptive immune response to cobalt-chrome (Co-Cr) wear particles. We report a case of a large pseudotumour that developed following a knee endoprosthetic replacement (EPR) undertaken for Ewing sarcoma. The lesion contained necrotic and degenerate connective tissue in which there were numerous scattered metal wear-containing macrophages, eosinophil polymorphs, lymphocytes, plasma cells and aseptic lymphocyte-dominated vascular-associated lesion-like lymphoid aggregates. Metal ion levels were elevated. No evidence of infection or tumour was noted and it was concluded that the lesion was most likely an inflammatory pseudotumour developing on the basis of an innate and adaptive immune response to components of Co-Cr metal wear derived from the knee EPR.

Original publication




Journal article


Skeletal radiol

Publication Date





967 - 974


Endoprosthesis, Knee, Metal wear, Pseudotumour, Adult, Arthroplasty, Replacement, Knee, Female, Femoral Neoplasms, Granuloma, Plasma Cell, Humans, Magnetic Resonance Imaging, Metals, Positron-Emission Tomography, Postoperative Complications, Prosthesis Failure, Sarcoma, Ewing, Stress, Mechanical, Surface Properties