RESUMEN
Peripheral ossifying fibromas are benign mesenchymal lesions that usually arise in the anterior maxilla of young female patients. Histologically they consist of spindle cell proliferation with focal mineralisation. We reviewed 48 specimens from 41 patients and recorded the clinical data, sex, and age of the patients, site and size of the lesions, treatment, and postoperative outcome. Histologically the presence of mature, woven bone, cementum, and calcifications were evaluated and evaluated immunohistochemically. Lesions were more frequent in female patients in the third and fourth decade, and were usually in the lower maxilla and smaller than 2cm. All lesions were conservatively excised, and they relapsed in eight patients. Histopathologically, the lesions were poorly circumscribed, moderately cellular proliferations, with no discernible architectural pattern. All tumours showed some degree of mineralisation, the presence of immature bone being the most common. Immunohistochemical examination showed staining of tumoural cells for smooth muscle actin and CD68. Lesions tended to occur more commonly in female patients, but one decade later than usually reported. We found a higher recurrence rate in lesions that contained cementum-like material but without bone formation, suggesting a lack of maturation in this group. Immunohistochemical results were consistent with myofibroblastic differentiation but they added no information about the behaviour of the lesions.