Fibrous dysplasia-like appearance of the frontal process of the maxilla on CT: prevalence in North China.

The frontal process of the maxilla occasionally shows a localized FD-like appearance. The purpose of this study was to determine its prevalence and findings on CT. A retrospective study of 1000 consecutive paranasal sinus CT scans was preformed on outpatients without a history of trauma or previous surgery in our hospital during 6 months. CT images were interpreted independently by 2 experienced head and neck radiologists on a PACS system in a bone window setting. Of the 1000 patients (546 males; 454 females), 51 (5.1%,41 males and 10 females) had an FD-like appearance in the frontal process of the maxilla. There was a statistically significant difference between sexes (P < .001). Twenty-nine (56.9%) entities arose from the right frontal process and 22 (43.1%) from the left frontal process. These entities, with well-defined margins, were located at the base of the frontal process of the maxilla, appearing as an ovoid or triangular configuration on axial-plane CT and as a spindle or elliptic shape on the coronal plane. The mean maximal diameter was 9.8 mm (range, 3.6-16.1 mm). These entities exhibited a pagetoid appearance (type I) in 37 (72.5%), a ground-glass appearance (type II) in 8 (15.7%), and a cyst-like appearance (type III) in 6 (11.8%) patients on CT. The FD-like appearance of the frontal process of the maxilla is not rare and can be readily detected by CT.