Giant cell tumor of bone of the skull mimicking multicentric giant cell tumor of bone revealed after dental consultation.

Giant cell tumor of the bone (GCTB) is a benign osseous neoplasm that primarily occurs in the epiphyses. Approximately 2% of GCTBs occur in the head and neck regions. Herein, we report a rare case of GCTB in the skull, which was discovered during a dental consultation. The patient was a 74-year-old man who had discomfort in the left temporomandibular joint for 3 months. During the initial visit, there were no remarkable clinical or radiological findings, and the patient was placed under observation. After 3 months, the patient was referred owing to a rapid, progressive swelling on the left side of the head. CT images revealed a slight area of contrast enhancement around the temporomandibular joint, where the patient initially experienced symptoms, but no definite mass was detected, whereas an expansive lesion with cortical thinning and erosion was identified in the left temporal region. Contrast-enhanced magnetic resonance imaging (MRI) revealed heterogeneous enhancement of the temporal lesion and a separate 10-mm lesion with similar enhancement on the inferior surface of the greater wing of the sphenoid bone. Aspiration biopsies of both lesions confirmed the diagnosis of GCTB. Initially, imaging raised the possibility of multicentric GCTB. Nevertheless, while the temporal lesion clearly originated from the bone, a characteristic feature of GCTB, the sphenoid lesion showed no evidence of an intraosseous origin on either CT or MRI. Therefore, this is a rare case of GCTB of the skull with a distinct progression pattern.