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.