Osteoclast-like multi-nucleated giant cells in uraemic tumoral calcinosis

A 46-year-old woman under 6-year haemodialysis was admitted for uncontrollable hip pain. An X-ray film revealed calcified mass around the 'left femur head', which was diagnosed as calcium deposition by percutaneous biopsy. Calcinotic tissues were removed surgically, and the resected specimen revealed tumoral calcinosis caused by low bone turnover. A complete resolution of calcinotic lesions around the 'left knee' occurred 6 months after treatment modification. Immunohistochemistry showed recruitment of multi-nucleated giant cells positive for CD68, tartrate resistant acidic phosphatase and calcitonin receptor, indicative of osteoclast-like features. We propose the involvement of osteoclast-like cells in active resorption of tumoral calcinosis.