What is non ossifying fibroma?

➢ Benign, likely reactive, mesenchymal proliferation ➢ May be present in as many as 50% of children and young adults aged 2–25 years. ➢ It is synonymous with fibrous cortical defect or metaphyseal fibrous defect if localized to the cortex or medulla, respectively. ➢ The findings are sufficiently specific on plain radiography that biopsy is rarely necessary. ➢ Fibroblastic cells arranged in a storiform (pinwheel) pattern admixed with lymphocytes and macrophages with foamy cytoplasm or multinucleated cells