Giant Cell Tumor of the Distal Humerus: A Rare Location With a Good Response to Denosumab.

Giant cell tumors (GCTs) are rare, benign, locally aggressive neoplasms. They typically affect the metaphyseal region; their occurrence at the distal humerus is rare, making their management challenging. We report the case of a 13-year-old girl, skeletally immature, admitted for a painful, progressive mass at her right elbow (circumference 26 cm) with functional limitation. Radiological evaluation by magnetic resonance imaging (MRI revealed a large osteolytic epiphysometaphyseal lesion of the right distal humerus, centered on the medial epicondyle and measuring 36 × 35 × 60 mm, with cortical rupture and soft-tissue invasion (Campanacci grade III). The bone biopsy revealed a GCT with no signs of malignancy. The staging workup was negative. Given the complex joint location and the patient's young age, the multidisciplinary team decided to initiate anti-receptor activator of nuclear factor-κB ligand (RANKL) therapy with denosumab (70 mg/m² subcutaneously (SC)) on days 1, 8, 15, and 28, followed by monthly administration, along with calcium and vitamin D supplementation. The seven-month follow-up was favorable: regression of the swelling (circumference 20 cm), complete joint release, and lesion stability on the follow-up MRI, with no calcium-phosphate complications. Denosumab is used in situations where surgery is not an option to reduce tumor size and control its progression. Its use increases the risk of calcium-phosphorus abnormalities and growth disorders. Our case demonstrated that a well-defined treatment regimen combined with calcium-phosphorus supplementation could control the aggressiveness of GCTs.