“…We present a case of synchronous gnathic OS and B-LBL in a teenager. Osteosarcoma was confirmed by histopathology, then a PET/CT scan revealed a suspicious distal lower limb activity discordant with metastasis; particularly given there were no pulmonary nodules (the typical primary site of mandibular OS metastases) [4] . Subsequent biopsy and histopathology revealed another primary B-LBL.…”