BackgroundThe squamous cell carcinoma is the most common subtype of malignant sinonasal tumours, predominantly involving the maxillary sinuses and nasal cavities in 70 to 80% of cases, and the frontal sinus is extremely rarely involved, in less than 1% of cases. Early clinical and radiological diagnosis is difficult due to overlap of findings with inflammatory sinonasal disease.Case presentationA 55-year-old Caucasian male patient had presented to the emergency department with three-month history of progressive right frontal swelling, acute frontal pain, recent exacerbation of right eye vision impairment and new lid swelling. There was no recent history of trauma and no neurological deficit on examination. Contrast-enhanced CT head was performed which demonstrated large bony destruction of frontal sinus with partly enhancing necrotic-looking tumour within the sinus. There was further intraorbital and intracranial extension of disease. Subsequent MRI confirmed these findings with better demonstration of intracranial and intraorbital component of the disease. The PET imaging did not reveal any avid disease elsewhere. Histopathology confirmed squamous cell carcinoma.ConclusionsFrontal sinus squamous cell carcinoma is a rare and the least common site within the paranasal sinuses. Early clinical and imaging diagnosis could be challenging; however, the index of suspicion should be high with indeterminate imaging findings. CT and MRI are the complimentary imaging techniques.