Juvenile Ossifying Fibroma: An Immunohistochemical Study

Abstract

Juvenile ossifying fibroma (JOF) is a nonmetastasizing, but locally aggressive and highly recurrent fibro-osseous lesion of the craniofacial skeleton. Microscopically, JOF consists of a cellular fibrous stroma containing a mineralized component in a psammomatoid or trabecular pattern. JOF should be distinguished from other bone tumors, including ossifying fibroma (OF) and osteosarcoma (OS). This study presents 5 cases of biopsy-proven JOF, trabecular-type, affecting 3 male and 2 female patients with a mean age of 11.8 years. Three cases arose in the maxilla and 2 occurred in the mandible. All cases were treated by enucleation; 2 cases recurred and were retreated with wide surgical excision. Immunohistochemical study of the OS-associated molecules CDK4, MDM2, and p53 was performed in all cases in addition to 5 control cases of OF. CDK4 positivity was noted in all JOF cases; the staining pattern was diffuse and strong in 4 cases and focal and weak in 1 case. In contrast, 4 cases of OF were weakly and focally CDK4 positive. Immunostaining for MDM2 was observed in 3 JOF cases; all OF were MDM2 negative. All cases of OF and JOF were negative for p53, except 1 focally positive JOF case. Considering the combined results of our previously published immunohistochemical studies of 34 head and neck OS, CDK4 expression is noticed in a high percentage of JOF, OS and OF, although the latter shows diminished staining. MDM2 expression is seen only in JOF and OS, being absent in OF. Finally, p53 expression is detected almost exclusively in OS, with the exception of a single case of JOF. Although significant overlap exists, differential protein expression patterns can elucidate the pathogenesis and facilitate the determination of aggressive or malignant behavior of bone tumors in the head and neck region.