Osteoblastoma of the Hyoid Bone

Discussion

Solid primary tumors of the hyoid bone are exceedingly rare, and reported cases have included plasmacytoma, osteosarcoma, giant cell tumor, aneurysmal bone cyst, osteoma, and chondrosarcoma.¹

Osteoblastoma is a rare bone tumor first described by Lichtestein and Jaffe as a distinct neoplasm in 1956. This disease accounts for 1%^3,4 or less⁵ of all bone tumors and most commonly involves the spine and sacrum of young individuals.² The second most common location is the mandible, followed by other craniofacial bones.³ Other more rare locations in the head and neck include the temporal bone, where 10 cases have been reported.⁴ Osteoblastomas of the larynx are also extremely rare, with only 4 cases reported up to 2008. Presumably most of these laryngeal osteoblastomas arose within ossifying cartilage, but one of them was thought to be extraosseous.⁶

Clinically, osteoblastomas present mainly with pain, swelling, and expansion of the bone cortex.² An osteoid osteoma is histopathologically similar but is smaller and is associated with pain that is often nocturnal and relieved with the use of aspirin or other NSAIDs.³ These typical symptoms occur in approximately 80% of the patients.³ Unlike osteoid osteoma, the pain of osteoblastoma usually does not respond to NSAIDs and is not generally more severe at night.⁵

Radiographic features of osteoblastoma are variable, usually showing a combination of radiolucent and radiopaque patterns, depending on the degree of lesional calcification, but without a sclerotic border or periosteal reactions.² An osteoid osteoma should demonstrate a radiographic nidus of <1 cm, whereas an osteoblastoma should measure >2 cm in greatest dimension. Neoplasms that measure between 1 and 2 cm fall into an arbitrary zone in which classification is determined by individual preference.³

The radiographic differential diagnosis for osteoblastoma includes other benign bone tumors. If a central calcified matrix is present, chondrosarcoma or enchondroma is an important consideration. If the lesion is lucent, aneurysmal bone cyst or other bone cysts should be considered. Other calcification patterns may suggest diagnoses such as ossifying fibroma or fibrous dysplasia.

Histologically, osteoblastoma is considered benign.⁵ It is a bone-forming tumor characterized by osteoid and woven bone deposition and abundant osteoblasts that are frequently in close association with newly formed bone. Occasionally, osteoblastomas may appear richly cellular, contain an abundant osteoclast-like component, and show plump osteoblasts that may evoke a diagnosis of osteosarcoma, thus leading to unnecessary overtreatment.² The histopathologic features are similar to those described for osteoid osteoma,³ and such resemblance is a particular challenge to the pathologist.⁵

In summary, this is the first report of a proved osteoblastoma of the hyoid bone. The radiographic appearance is most easily confused with low-grade chondrosarcoma or other benign calcifying bone tumors.