Sinonasal Squamous Cell Carcinoma Mimicking a Brain Abscess: Report of a Unique Case.

Sinonasal cancers are rare tumors with squamous cell carcinoma (SCC) being one of the more common histological subtypes. These carcinomas typically invade the sinus cavity from which they originate, progressively eroding surrounding bony structures and extending to adjacent anatomical regions. In rare instances, they may breach the posterior or superior walls to invade the anterior cranial fossa (ACF) and frontal lobes. The normal flora of the nasal cavity and paranasal sinuses includes Staphylococcus aureus, Staphylococcus epidermidis, α- and γ-streptococci, Propionibacterium acnes, and aerobic diphtheroids. To our knowledge, cases of sinonasal malignancies extending into the frontal sinus and ACF, leading to a frontal lobe abscess caused by these organisms, have not been well-documented. We present a case of a 36-year-old male who underwent surgery for a right frontal brain abscess caused by Staphylococcus aureus. Histopathological analysis of the abscess wall revealed moderately differentiated SCC arising from the paranasal sinuses, highlighting a rare and intriguing presentation of this disease.