Diagnostic Dilemma: Atypical Giant Cell Tumor of Bone Versus Primary Giant Cell Sarcoma

Abstract

Abstract Giant cell tumors of bone (GCTBs) are rare tumors that are locally aggressive but benign. Malignant transformation is described after multiple resections, although more commonly after irradiation. However, there exists a rare variant of GCTB that is malignant in nature. We present a case of a 24-year-old man presenting with 6 weeks of thigh pain. Biopsy demonstrated a benign-appearing GCTB, and final pathology after intralesional curettage yielded the same diagnosis. At 12 weeks postoperatively, a biopsy was performed for a recurrence on imaging, and two independent pathologists confirmed a recurrent GCTB. Single-agent chemotherapy was initiated, yet the patient developed an enlarging soft tissue mass at the same location along with new pulmonary nodules. The patient underwent a third biopsy of the thigh mass as well as a pulmonary wedge resection. The diagnosis at this time was primary giant cell sarcoma of bone. The patient subsequently underwent osteosarcoma-based chemotherapy and above-knee amputation. At 14-month follow-up, patient was found to have biopsy-proven recurrent pulmonary metastatic disease. The differential diagnosis for giant cell rich tumors is broad, and it is often difficult to distinguish benign GCTB from their malignant counterparts. The importance of a multidisciplinary approach involving pathology, medical oncology, radiology, and orthopedic surgery is paramount in difficult and rare cases to establish the proper diagnosis and treatment plan.