Cysts that sinus mucosa, often due to pressure and thinning, so that the cells lose cilia, but also due to chronic inflammation and fibrosis, the normal pseudostratified ciliated columnar epithelium can be seen under the chronic inflammatory infiltration, sometimes polyp-like, between the visible glands are cystic enlargement, cyst contents are mostly yellowish, tan or dark green viscous liquid, sometimes bloody, containing cholesterol, the longer the disease, the higher the concentration, from plasma, mucus The longer the disease, the higher the concentration, from plasma, mucous, cheese-like to gum-like, secondary infection, the liquid is filled with pus cells, cysts develop slowly, gradually increasing, sinus wall bone compression thinning, sinus wall smooth, larger pterygoid sinus cysts can compress and destroy adjacent bone such as optic nerve foramen, orbital tip, supraorbital fissure, saddle back and sieve sinus, etc., late frontal sinus mucous cysts can destroy the posterior wall of the frontal sinus, so that the mucosa and dura mater adhesion to form epidural mucous cysts. 1.X-ray: X-ray examination often reveals cloudy sinus shadow with enlarged sinus cavity on the affected side. 2.Ultrasound: cystic masses have a typical presentation on ultrasound. ultrasound shows: the lesion is usually located above or medial to the orbit, the lesion shape is round or oval or irregular shaped occupying lesion, and the internal echo is very weak. The posterior border of the cyst may be smooth or irregular, and a large cystic mass may be found superiorly or medially in the orbit on pars plana scan.A ultrasound shows: a typical image of a cystic mass with large volume, low internal reflection, poor attenuation, and a clear lesion border with a high wave crest in and out of the cyst. At this point, it is easy to misdiagnose as an intraorbital lesion. If the diameter of the lesion is found to be significantly larger than the distance between the eye and the orbital wall, the possibility of intraorbital spread of sinus tumor should be considered first, and of course, the possibility of intraorbital spread of the lesion to the sinus cannot be excluded. The echogenicity or reflection within the cyst may vary slightly according to the content of the lesion: if the mucus is of uniform density, the ultrasound may show no echogenicity or liquid flat segment; if there is a mass of pus or other organic components mixed with the mucus, the ultrasound may show weak echogenicity. 3.CT scan: The lesion is seen to originate from the frontal sinus, septal sinus or frontal septal sinus, with enlarged sinus cavity, increased density and homogeneity, and coronal CT better shows the relationship between the lesion and the orbit. The sinus wall often disappears due to chronic compression, and the cyst invades the orbit, causing displacement of intraorbital structures. If the intracapsular fluid enters the orbit through the ruptured orbital periosteum, orbital abscess or cellulitis symptoms and imaging appear. If the cyst occurs in the frontal sinus and the lesion invades superiorly to the orbit, it is easily misdiagnosed as an orbital primary tumor on transaxial CT because transaxial CT cannot show the relationship of the lesion to the sinus. Larger mucus cysts may compress the orbital bone wall and become thin, resorb or even absent. 4.MRI: Different periods of the lesion may have different signal intensities. At the beginning of the lesion, due to the large amount of water in the mucus, the T1WI is low signal and the T2WI is high signal. In the chronic phase protein concentration increases water absorption gradually, the cyst is high signal in T1WI and T2WI, longer lesions are low signal in T1WI and T2WI If it is a mucus abscess, the viscosity of the infected component increases leading to T1 shortening, the cyst itself has no enhancement phenomenon, while the cyst wall has signal enhancement.