Surgical management of GCT of the sacrum is more complicated, mostly as a result of late discovery, large size, spinal or pelvic instability, and frequent involvement of nerve roots [15–17]. In case of extended involvement of the proximal part of the sacrum, total sacrectomy has been advocated, as it has been associated with low local recurrence rates (0–8%) [18]. However, as there is a high risk of infection (18–46%), neurological deficits (24–38%), and bladder, rectal, or sexual dysfunction (18–47%), it could be considered overtreatment for an essentially benign tumor [64, 71]. Partial sacrectomy is less mutilating and can be performed for sacral involvement distal to the S2 segment, allowing for preservation of bowel and bladder function without the need for lumbopelvic reconstruction [4]. Marginal resection can be performed for lesions distal to the S3 segment.

Curettage is less invasive, permitting salvage of nerve roots and visceral structures and maintenance of intrinsic spinal or pelvic support. However, curettage results in relatively high recurrence rates, ranging from 10 to 37% [25]. Caution is warranted with the application of local adjuvants such as phenol or liquid nitrogen in the vicinity of neurovascular structures, as they can induce local necrosis and transient nerve damage [18]. After curettage, spinal or pelvic stability should be assessed and stabilization performed if needed. If at least S1 is preserved after intralesional resection, reconstruction is generally unnecessary. If S1 is partially or completely resected, stabilization with iliolumbar screw fixation is preferred [25].

Selective arterial embolization can be performed serially as primary treatment, or a precursor to surgery to reduce bleeding, as these tumors can be associated with occasional catastrophic intraoperative hemorrhage [16, 33–35]. Systemic therapy alternatives for GCT include bisphosphonates, IFN-a, and denosumab. Denosumab is a human monoclonal antibody and RANKL inhibitor that blocks osteoclast maturation and thus its osteolytic properties. It is currently approved for osteoporosis treatment in postmenopausal women at risk for fracturing, to increase bone mass in patients with prostate or breast cancer who are at risk for fracture due to androgen deprivation therapy or aromatase inhibitor therapy, respectively, and for the prevention of skeletal-related events in patients with bone metastases from solid tumors. It has also been approved by the FDA for the treatment of adults and skeletally mature adolescents with GCTB that is unresectable, or when surgical resection is likely to result in severe morbidity [72]. A recent study has shown clear clinical benefits of denosumab therapy [73]. Finally, another GCT treatment modality is represented by radiotherapy. More used in the near past, it has now gone in misuse, due to concerns for radiation-induced sarcoma. The reported risk of malignant transformation varies between 0 and 5% [74, 75]. Nowadays, radiotherapy should be restricted to those rare cases of unresectable, residual, or recurrent GCTB in which treatment with RANKL inhibitors is not possible or has been proven to be ineffective and when surgery would lead to unacceptable morbidity.