Giant Cell Tumor of the Temporal Bone

Significance Statement

GCTB is a rare benign tumor that is aggressive and can destroy the surrounding bone. GCTB arising in the temporal bone is exceptionally rare. Treatment of GCTB requires surgery, and denosumab is a treatment option. We present the characteristic imaging features with osteolytic extension and the management of GCTB of the temporal bone.

Giant cell tumor of bone (GCTB) is an exceptionally rare benign tumor that typically arises at the ends of long tubular bones. ¹ GCTB is not cancerous, but is aggressive and can destroy the surrounding bone. Treatment for GCTB almost always involves surgery to remove the tumor. Another treatment option is denosumab, a monoclonal antibody against the receptor activator of nuclear factor kappa-B ligand (RANKL). Denosumab is effective in locally advanced disease and in metastatic GCTB.

The temporal bone is much less commonly affected by GCTB than the long tubular bones. The temporal bone is anatomically complex because it is located near the brain and contains many vital nerves and vessels. This anatomical and functional complexity makes it difficult to treat GCTB of the temporal bone, and surgery alone can lead to severe morbidity. In such cases, a multidisciplinary treatment approach of surgery in combination with denosumab may balance disease cure with function preservation. Here, we present a case of GCTB in which imaging played a critical role in evaluation of a rare tumor of the temporal bone.

A 68-year-old woman was referred to our department for evaluation and treatment of a mass lesion in the right temporal bone. The patient had first noticed a fullness sensation in the right ear a month earlier, but denied vertigo, facial nerve palsy, or ear pain. On examination, the external auditory canal was narrowed due to pulsatile swelling of the anterior wall. A pure-tone audiogram revealed moderate conductive hearing loss in the right ear. Non-contrast computed tomography (CT) showed a 2.5-cm diameter mass lesion in the right temporal bone with osteolytic extension (Figure 1A and B). The lesion had partially destroyed the mastoid air cells; the remaining intact air cells were filled with soft tissue density. The tympanic cavity was also affected, with no evidence of erosion of the ossicles or facial nerve canal. The otic capsule, including the vestibule, semicircular canals, and cochlea, was preserved. The skull base bone of the middle cranial fossa, which was in contact with the mass lesion, was absent. A 3D reconstruction of dynamic CT angiography showed vessels branching off from the middle meningeal artery, which supplied blood to the mass (Figure 1C). T1-weighted magnetic resonance imaging showed the lesion as low-intensity signals (Figure 2A) that were enhanced by gadolinium administration (Figure 2B). The mass lesion pressed locally on the brain parenchyma, but with no direct effect. T2-weighted imaging showed heterogeneous low-intensity signals without clear demarcation from adjacent soft tissue. Mastoid effusion was also shown.

Figure 1.

(A) Axial temporal bone CT scan shows a right-sided expansive osteolytic mass lesion (arrow). The tympanic cavity and mastoid air cells are involved, but there is no erosion of the ossicles, otic capsule, and facial nerve. (B) Coronal temporal bone CT scan shows the absence of the right mastoid tegmen (arrows). (C) Three-dimensional reconstruction of dynamic CT angiography of the right external carotid artery system shows vessels (arrows) branching off from the middle meningeal artery that supply blood to the mass lesion (asterisk).

Figure 2.

(A) Axial non-contrast T1-weighted image shows a heterogeneous low-intensity mass occupying the temporal bone. (B) Axial post-contrast T1-weighted image shows an enhancing mass with forward displacement of the temporal lobe. The brain parenchyma is not directedly affected. (C) Axial T2-weighted image shows a heterogeneous hypo-intense mass in contact with the temporal lobe. Mastoid air cell effusion is apparent.

A biopsy was performed from the external auditory canal, which resulted in diagnosis of GCTB. Treatment consisted of a transtemporal approach to the skull base with resection of the mass and adjuvant denosumab administration. During surgery, the lesion was found to be a well-vascularized, soft, gray mass involving the dura of the middle cranial fossa. The mass lesion was firmly fused to the dura and was gradually removed with bipolar coagulation. The wound defect was filled with an abdominal fat graft. Histopathology was suggestive of GCTB. The differential diagnosis includes giant cell granuloma ² and fibrous dysplasia. In the younger population, rhabdomyosarcoma and osteosarcoma should also be differentiated.