Bone tumour of the finger. Giant cell tumour (GCT) affecting the finger of a 90 year old female patient. GCTs, or osteoclastomas, are rare benign (non-cancerous) tumours that affect the bone. They normally occur in adults between 20 and 40 years of age. If not treated, the tumour will continue to grow and eventually destroy the bone. Surgical removal is the most effective treatment.