Fibrous Histiocytoma in the Far Lateral Frontal Sinus-A Rare Observation.

This report describes a rare occurrence of benign fibrous histiocytoma in the frontal sinus of a 38-year-old male. The patient presented with acute symptoms, including sudden-onset headache, nausea, and general discomfort, although neurological, otorhinolaryngological and laboratory examinations showed no abnormalities. A cranial CT scan revealed a cystic, osteodestructive lesion measuring 2.5 cm in the far lateral right frontal sinus, initially suspected to be a mucocele due to radiological characteristics and the patient's history of recurring frontal headaches and retrobulbar pressure. Elective surgical excision was performed via an external supraorbital approach due to the lesion's lateral location. Histopathological examination of the excised tissue revealed characteristic features of benign fibrous histiocytoma, including spindle cell proliferation and the presence of histiocytes and siderophages. Immunohistochemistry further supported the diagnosis, showing EMA, S100, and creatinine negativity with SMA positivity. This case is unique, as it represents the first reported benign fibrous histiocytoma in the frontal sinus. During regular follow-up, the patient remained symptom-free and showed no recurrence. This report underscores the importance of considering rare diagnoses for cystic skull lesions and supports tailored surgical approaches based on lesion location.