XRay shows an eccentric multiloculated lytic lesion with sclerotic margins abutting the cortex in the distal diaphysis of the femur.
Bland multinucleated giant cells are scattered throughout.
The classic picture is that of an interwoven fascicular fibroblastic proliferation with moderate numbers of multinucleated giant cells.
A storiform pattern of spindle cells with somewhat plump vesicular nuclei is appreciated. Note the hemosiderin deposition (top center).
Clusters of foamy macrophages are also not uncommon. In fact, if composed predominantly of foamy cells and cholesterol crystals, the lesion is termed a xanthoma and may represent at end stage of nonossifying fibromas (Fletcher).
Some areas have more stromal collagenization than others, again with interspersed xanthomatous cells.
The term metaphyseal fibrous defect is preferred over nonossifying fibroma by some authors, as it is a benign reactive lesion rather than a true neoplasm. These lesions arise in the metaphysis of skeletally immature individuals (younger than 20), often in the insertion of tendons. As the bone grows, these lesions migrate toward the diaphysis. It is thought to be an exaggerated osteoclastic resorption of bone (Fletcher, Folpe).
Imaging shows a muliloculated radiolucent defect with a sclerotic, scalloped border. Histologically, the picture is that of a proliferation of spindled cells in a storiform pattern. Giant cells, foam cells and hemosiderin pigment deposition are randomly distributed (Fletcher).
In an area with giant cells, you might think of giant cell tumor of bone in your differential, however, GCT occurs in skeletally mature individuals and is centered on the epiphysis, whereas nonossifying fibromas arise in skeletally immature individuals and arise in the metaphysis.
80% of cases arise in the distal femur and proximal tibia. Most patients are teenagers and are usually discovered incidentally. Rarely, multiple nonossifying fibromas are seen with cafe-au-lait spots in the setting of Jaffe-Campanacci syndrome.
Usually self healing lesions that do not usually require treatment. Larger lesions that expand the bone are prone to fracture and may require curettage and bone grafting.
→Proliferations of fibrous tissue that arise in the metaphysis of long bones in skeletally immature individuals.
→Usually asymptomatic and discovered incidentally on imaging.
→Multiple nonossifying fibromas with cafe-au-lait spots occur in the setting of Jaffe-Campanacci syndrome.
Fletcher CDM, ed. Diagnostic Histopathology of Tumors. 3rd Ed. Philadelphia, PA: Elsevier; 2007: 1638.
Folpe AL, Inwards CY. Bone and Soft Tissue Pathology: Foundations in Diagnostic Pathology Philadelphia, PA: Elsevier; 2010: 355-358.