CT and MR imaging characteristics of histological subtypes of head and neck ossifying fibroma.

OBJECTIVES The current study aimed to assess CT and MRI characteristics of histological subtypes of head and neck ossifying fibroma (OF). METHODS 12 patients with histopathologically-proven head and neck OF were included in this study. Lesions were pathologically classified into three histological subtypes: eight cement-OFs (COFs), three juvenile psammomatoid OFs (JPOFs), and one juvenile trabecular OF (JTOF). All patients underwent CT examination, while seven also underwent MRI. Imaging characteristics were retrospectively assessed. RESULTS On CT images, the lesion margins were well-defined in nine patients (75%) (seven COFs and two JPOFs), partially ill-defined in two (17%) (one COF and one JTOF), and ill-defined in one (8%) (one JPOF). The continuity of the eroded overlying bone cortex was maintained in nine patients (75%) (seven COFs and two JPOFs) but disrupted in three (25%) (one COF, one JPOF, one JTOF). With respect to lesion density, homogeneous ground-glass opacity was observed in five patients (42%) (five COFs), target-like appearance in three (25%) (two COFs, one JPOF), and mixture of hyper- and hypodense areas were observed in four (33%) (one COF, two JPOFs, one JTOF). MR signal intensity was homogeneous in two patients (29%) (two COFs) and heterogeneous in five (71%) (two COFs, two JPOFs, one JTOF). CONCLUSIONS COFs tended to exhibit well-defined margins and preserved continuity of the overlying bone cortex. COFs were usually homogeneous, whereas JPOFs and JTOF were always heterogeneous. Target-like appearance was one of the characteristics of OFs, but it was observed in both COF and JPOF.