Aim This case report aims to present a rare instance of sphenoid sinus metastasis in a patient with hepatocellular carcinoma (HCC). The discussion contextualizes this case within existing literature. Method A 56-year-old man was admitted under General Medicine with progressively worsening headache, associated with photophobia, rhinorrhoea, and paranasal pain. Medical history included untreated chronic hepatitis B and a recent diagnosis of HCC. Cranial nerve examination was unremarkable. Computed tomography showed right maxillary opacification, and dehiscence of the left sphenoid sinus lateral wall. Multidisciplinary review suggested findings were consistent with invasive fungal sinusitis with osteomyelitis. Results The patient proceeded to functional endoscopic sinus surgery. Frank pus was encountered in the right maxillary sinus. Left sphenoidotomy revealed an encapsulated lesion with a necrotic core. There was no macroscopic evidence of brain parenchymal herniation or cerebrospinal fluid leak. Post-operatively, his photophobia and headaches improved. Histology from the left sphenoid sinus showed necrosis with cellular tumour elements, suggestive of a metastatic deposit. Fungal staining and cultures were negative. The patient was referred to Gastroenterology for further management. Conclusion The sphenoid sinus is a rare metastatic site, and a hepatic source is exceedingly rare. Surrounding anatomy can result in varied presentations. Literature suggests a poor prognosis is associated with sphenoid metastasis. A sphenoid lesion in the context of recent cancer diagnosis should raise suspicion for metastasis. Targeted pathological testing should be considered. References 1. Mickel RA, Zimmerman MC. The sphenoid sinus - A site for metastasis. Otolaryngol - Head Neck Surg. 1990;102(6):709–16. 2. Chang MH, Kuo YJ, Ho CY, Kuan EC, Lan MY. Metastatic tumors of the sinonasal cavity: A 15-year review of 17 cases. J Clin Med. 2019;8(4).