Cholesterol granuloma (CG) is common in the mastoid air cells, less common in the skull base and orbit, and uncommon in the paranasal sinuses. The most commonly affected sinus is the maxillary sinus, and it is very rare in the ethmoid and sphenoid sinus. CG is thought to be due to impair the venous and lymphatic drainage from the sinus cavity. In the early period of the disease, the patient has no symptoms but when the expanding cysts compress the surrounding structures, they cause bony erosion that leads to clinical symptoms such as nasal blockage, eye pain or visual loss. If the patients’ presentation does not correlate with physical examination, concerns are raised, and imaging should be performed.
This study reports a case of cholesterol granuloma of the ethmoid sinus treated with the endoscopic marsupialization
technique. This paper will remind physicians of the characteristics of cholesterol granuloma, which are useful for differential diagnosis of patients with this condition. In addition, it is the first reported case of cholesterol granuloma of the ethmoid sinus in the Thai literature.

Keywords: Cholesterol granuloma, Ethmoid sinus, Endoscopic marsupialization technique