Giant Cell Tumor of the Distal Ulna in an Elderly Patient on Hemodialysis: Diagnostic Challenge and Surgical Management.

Giant cell tumor of bone is a locally aggressive tumor that usually affects the epiphyseal region of long bones in young adults. Involvement of the distal ulna is rare, and the diagnosis in elderly patients with end-stage chronic kidney disease may be difficult because brown tumors related to secondary hyperparathyroidism can mimic giant cell tumor radiologically and histologically. We report the case of a 69-year-old woman with end-stage chronic kidney disease on hemodialysis who was admitted for a painful and progressively enlarging mass on the ulnar border of the left wrist that had been present for six months. Standard radiographs showed a well-defined, expansile osteolytic lesion of the distal ulna involving the epiphysis and metaphysis, with cortical thinning and no obvious periosteal reaction. Surgical biopsy demonstrated a proliferation of mononuclear stromal cells associated with numerous osteoclast-like multinucleated giant cells, compatible with a giant cell tumor. Given the hemodialysis background, a brown tumor was discussed; however, serum calcium, phosphate, and parathyroid hormone levels were within normal limits, and histology favored a giant cell tumor. The extension workup showed no secondary localization. The patient underwent en bloc resection of the distal ulna according to a Darrach-type procedure, associated with flexor carpi ulnaris tenodesis to improve the stability of the ulnar stump. Histopathological examination of the surgical specimen confirmed the diagnosis. At eight months of follow-up, the outcome was favorable, with satisfactory wrist function, a stable radiographic appearance, and no clinical or radiological recurrence. This case highlights the importance of clinicobiological and histopathological correlation when evaluating a giant-cell-rich bone lesion in a dialysis patient. It also supports the value of distal ulna resection associated with soft-tissue stabilization as a pragmatic option in selected elderly patients.