Benign Fibrous Histiocytoma of Bone

Benign fibrous histiocytoma of bone (also known as fibroxanthoma, fibrous xanthoma, xanthofibroma, and xanthogranuloma) is a rare benign lesion that is histologically indistinguishable from non-ossifying fibroma, but with location and clinical or radiographic presentation atypical for non-ossifying fibroma.

In contrast to non-ossifying fibroma, patients are often older, with 60% older than 20 years of age. Patients are also often symptomatic (85% of cases) and present with pain in 65% of cases. The location is also atypical for non-ossifying fibroma, with epiphyseal and diaphyseal localization being common in the long bones. The lesions can also occur in the pelvic bones in 25% of cases (virtually any bone can be involved). Also in contrast to non-ossifying fibroma, benign fibrous histiocytoma of bone can be locally aggressive and recur after curettage or excision.

Radiographic findings can be similar to non-ossifying fibroma, including a well-defined, radiolucent lesion with a sclerotic border. The sclerotic border can be absent in 1/3 of cases. Internal trabeculation or pseudoseptation can be present in some cases. The lesion can either be medullary (more common in general) or eccentric (more common with epiphyseal lesions). More aggressive features, such as endosteal thinning and bone expansion, can be seen. A periosteal reaction is usually not seen in the absence of superimposed pathologic fracture.

MRI findings include intermediate signal intensity on T1-weighted images and high signal intensity on T2-weighted images.

Differential considerations include:

• Non-ossifying fibroma: May be indistinguishable from benign fibrous histiocytoma
• Giant cell tumor: Rarely has a rim of reactive sclerosis, which is common in benign fibrous histiocytoma. Some consider benign fibrous histiocytoma a burned-out giant cell tumor.
• Intraosseous ganglion: Usually smaller than benign fibrous histiocytoma of bone, but may be considered in cases of epiphyseal lesions.
• Chondromyxoid fibroma:
• Osteoblastoma: Usually has a periosteal reaction and looks like osteoid osteoma, but can also appear as an expansile lucency with a sclerotic rim and internal calcifications. The internal calcifications can simulate a chondroid matrix and can help differentiate this presentation of osteoblastoma from benign fibrous histiocytoma of bone.

benign fibrous histiocytoma of bone should be distinguished from benign fibrous histiocytoma of soft tissues.

References

• Greenspan A, Jundt G, Remagen W. Fibrogenic, Fibroosseous, and Fibrohistiocytic Lesions. In Differential Diagnosis of Orthopaedic Oncology, 2nd Edition. 2007 Lippincott Williams & Wilkins; pp 266-267.
• Kyriakos M. Benign fibrous histiocytoma of bone. In World Health Organization Classification of Tumours: Pathology and Genetics of Tumours of Soft Tissue and Bone. Fletcher CDM, Unni KK, Mertens F (eds). IARCPress Lyon, 2002. pp 292-293.