Dedifferentiated giant cell tumour of bone in the form of low-grade fibroblastic osteogenic sarcoma: case report of a unique presentation with follow-up

A. Nahal, A. Ajlan, T. Alcindor, R. Turcotte


Giant cell tumour (GCT) of bone is a locally aggressive benign tumour. It can, however, undergo dedifferentia­tion, either de novo or secondarily after local recurrence or radiation. Whether spontaneously occurring or in­duced by previous irradiation, this malignant transfor­mation is typically defined as a high-grade anaplastic sarcoma devoid of giant cells. Dedifferentiation of GCT into low-grade-appearing sarcoma has not been reported yet. Here, we describe the first case of dedifferenti­ated GCT in the appearance of low-grade fibroblastic osteogenic sarcoma with distant bone metastases. This disease progression occurred without previous irradiation. We confirm the aggressive behaviour of this tumour despite the deceptively bland appearance of the malignant component. We also alert others to the importance of recognizing this rare histology to avoid underdiagnosis and subsequent undertreatment.

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ISSN: 1198-0052 (Print) ISSN: 1718-7729 (Online)