Background and purpose: Giant cell tumor (GCT) of bone, a locally aggressive albeit benign neoplasm, accounts for 3%-8% of all primary bone tumors. Approximately 60%-70% of patients with GCTs of bone are 20-40 years of age, whereas GCTs are very rare in those above the age of 55 years. Although many case studies on GCTs have been published, extensive search of the literature reveals few reports of elderly patients with GCTs. One case series of ten elderly patients with GCT of bone has reported that there were no differences in the characteristics of GCTs including tumor location, radiographic features, and clinical course present the case of a 74-year-old female with aggressive GCT of the left femoral condyle with an extended lesion, which was misdiagnosed by imaging studies.