486 Aggressive fibro-osseous lesion of the temporal bone

Purpose of study To present a rare case of a clinically aggressive temporal bone tumour that was described as a benign fibro-osseous lesion (BFOL) on pathology, as well as to highlight the surgical resection approach and literature on temporal bone BFOLs. Methods used A 53-year-old male presented with several months of left-sided hearing loss and non-pulsatile tinnitus. Imaging revealed a destructive lesion eroding through the left temporal bone toward the jugular foramen. The patient received a mastoidectomy followed by a revision mastoidectomy a year later. All pathological specimens were consistent with a BFOL. The patient developed left facial weakness 3 months after the revision as the erosive lesion continued to invade the temporal bone and approach the jugular bulb despite its benign histopathologic appearance. Summary of results Two years later, the patient received a resection via a lateral skull base approach which resulted in dramatic improvement of compressive symptoms. Conclusions Temporal bone BFOLs are rare and even more rarely feature an aggressive clinical course. This case demonstrates a particularly destructive presentation of a temporal bone BFOL and also emphasises that temporal bone tumours benign on histopathology may be clinically aggressive. Early and complete resection seems to be required for such histologically benign yet locally destructive lesions. These aggressive clinical entities should be considered when fine needle aspirates or biopsies suggest benign-appearing fibro-osseus lesions.