A Rare Case of Osteoblastic Osteosarcoma of the Temporal Bone and Comprehensive Review of the Literature.

Introduction: Although osteosarcoma represents the most common primary malignant bone tumor in children, they comprise only 0.2% of all cancers. Osteosarcoma frequently involves long bones; however, 8% of osteosarcomas involve the skull or mandible. Osteosarcoma is generally categorized based on location within the bone (central, surface, or extraskeletal) and histological grade (high-grade or low-grade). Osteoblastic osteosarcoma is a central, high-grade subtype and may be difficult to diagnose; it may present similarly to osteoblastoma, another rare, but benign, type of osteoblastic bone tumor. In this report, we present a rare case of osteoblastic osteosarcoma involving the temporal-occipital skull.

Study Design: Case report and systematic review.

Setting: Tertiary referral center.

Results: A 21-year-old male presented for assessment of a mass appearing over his left mastoid region, first noticed within the previous 12 months. He experienced growth of the lesion and pain that increased when pressure was applied to the mass. Results from fine needle aspiration and CT-guided core biopsy were positive for osteosarcoma, osteoblastic-type. Magnetic resonance imaging of the brain and skull base revealed the mass to be 2.8 cm in maximal diameter. Given a somewhat favorable location, the tumor could be completely excised en bloc with negative margins, and the patient subsequently received adjuvant chemotherapy. The patient is doing well at last follow-up 10 months after surgery, with no evidence of recurrence to date.

Conclusion: The temporal bone is an uncommon location for a primary osteosarcoma, and there are numerous conditions that could present in a similar manner. This case highlights this rare occurrence of osteoblastic osteosarcoma of the temporal bone without previous exposure to radiation. There are a limited number of similar cases in the literature, and our report serves to bring awareness to this potential diagnosis and considerations related to treatment.