Epidemiology
It usually appears in young adults, near joints, once the growth plates have closed. Because it usually sits next to the joint, treatment aims to control the lesion without unnecessarily damaging the joint surface.
Basic features
Locally aggressive; it can destroy subchondral bone and cause pain, joint effusion, or fracture. The diagnosis is supported by the characteristic mutation of the H3-3A gene (H3F3A G34W), detectable on the biopsy, which separates it from other giant cell-rich lesions that look similar.
Usual treatment
Extended curettage with grafting or cement filling is the most common treatment, because it preserves the joint. En-bloc resection is the alternative, and is preferred when the bone or the joint surface is badly destroyed, when there is a pathologic fracture that cannot be reconstructed, in recurrences after curettage, or in expendable bones; it controls local disease better, but it means the segment has to be reconstructed. Denosumab is used in specific situations (unresectable tumors, complex recurrences, or to facilitate a difficult operation): it controls the lesion and hardens its rim, but it does not cure it. It is not used routinely before curettage, because in that sequence it has been associated with more local recurrence. In addition, the disease often reactivates when it is stopped, so the decision to start it and for how long is taken by an experienced team. In young patients, withdrawal also requires medical and laboratory monitoring, because stopping it can cause a marked rise in blood calcium.
Outcomes and prognosis
Moderate risk of local recurrence after extended curettage and low after wide resection. In a small proportion it produces benign lung implants, so it requires prolonged follow-up.