Giant cell tumor of the bone: aggressive case initially treated with denosumab and intralesional surgery.

Giant cell tumor of the bone (GCTB) is a locally aggressive benign tumor, which has historically been treated with wide surgical excision. We report a case of a 29-year-old male with histology-proven GCTB of the distal ulna. The initial imaging study was a contrast-enhanced magnetic resonance imaging (MRI) examination of the left wrist, which was from an outside facility performed before presenting to our institution. On the initial MRI, the lesion had homogenous T2-hyperintense and T1-hypointense signal with expansive remodeling of the osseous contour. A radiographic study performed upon presentation to our institution 1 month later showed progression of the lesion with atypical imaging characteristics. After confirming the diagnosis, denosumab therapy was implemented allowing for reconstitution of bone and intralesional treatment. The patient was treated with five doses of denosumab over the duration of 7 weeks. Therapeutic changes of the GCTB were evaluated by radiography and a post-treatment MRI. This MRI was interpreted as suspicious for worsening disease due to the imaging appearance of intralesional signal heterogeneity, increased perilesional fluid-like signal, and circumferential cortical irregularity. However, on subsequent intralesional curettage and bone autografting 6 weeks later, no giant cells were seen on the specimen. Thus, the appearance on the MRI, rather than representing a manifestation of lesion aggressiveness or a non-responding tumor, conversely represented the imaging appearance of a positive response to denosumab therapy. On follow-up evaluation, 5 months after intralesional treatment, the patient had recurrent disease and is now scheduled for wide-excision with joint prosthesis.