Abstract
The incidence of distant metastases in head and neck squamous cell carcinoma (HNSCC) is relatively small in comparison to other malignancies and the rate of development of a bony second primary in a patient with HNSCC even smaller. Presence of a second primary
adversely impacts the survival and may significantly alter treatment planning . Pulmonary secondaries and second primaries are the most frequent in SCC. A bony second primary in HNSCC is rare and not reported. In this article, we report the case of a patient with oral cavity malignancy that developed osseous second synchronous primary to the distal end of the femur.
The diagnosis was made based on x-ray findings, bone scan findings and bone biopsy. We report this case because we believe that a second primary of osteoclastoma at the distal femur along with an oropharyngeal carcinoma has never been reported and to emphasize on the importance of awareness of the possibility of the development of osseous second primaries mimicking osseous metastasis in head and neck cancer, although it is not a common
phenomenon.

Key words: synchronous malignancy head and neck, head and neck malignancy and bone malignancy