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Benign Fibrous Histiocytoma

Summary

This tumor has been given the names benign fibrous hystiocytoma, fibrous histiocytoma, xanthofibroma, fibroxanthoma of bone, and primary xanthoma of bone. The author of this site prefes the name benign fibrous histiocytoma.

There is no defined age group for this tumor except that patients are generally older than those found with a non-ossifying fibroma.
Clinically, patients report pain from the lesion, often of months or years duration. Pain may be associated with pathological fracture. There may be some local tenderness, but no swelling or mass is seen, and there are no systemic symptoms. There is normally no impairment of the function of the nearby joint. Spinal lesions may cause neurologic defect by pressing on the spinal cord.
It has a lytic, loculated appearance with prominent sclerosis of the edges of the lesion.
Treatment consists of careful and complete curettage and filling of the defect with graft material, bone cement, or other suitable bone void filler.
Complete Information on this Tumor
Introduction and Definition: 

This tumor has been given the names benign fibrous hystiocytoma, fibrous histiocytoma, xanthofibroma, fibroxanthoma of bone, and primary xanthoma of bone. The author of this site prefes the name benign fibrous histiocytoma.

There is disagreement amongst pathologists as to whether this tumor represents a true neoplasm, adevelopmental defect, or a reactive process. A portion of the confusion arises from the lack of agreement between pathologists as to what exactly defines this lesion. Different pathological, clinical and radiographic definitions of this lesion have led to different findings of frequency, age range, location in the skeleton, histological appearance, and tumor behavior. The authors of this site have combined information from their own personal experience and a number of published sources to create this summary. For additional information please refer to the primary sources listed in the references section.

Incidence and Demographics: 
There is no defined age group for this tumor except that patients are generally older than those found with a non-ossifying fibroma.
Symptoms and Presentation: 

Clinically, patients report pain from the lesion, often of months or years duration. Pain may be associated with pathological fracture. There may be some local tenderness, but no swelling or mass is seen, and there are no systemic symptoms. There is normally no impairment of the function of the nearby joint. Spinal lesions may cause neurologic defect by pressing on the spinal cord. In some cases there is a primary underlying disorder of cholesterol metabolism or other lipid abnormalities. In these cases the lytic bone lesions are analogous to those seen in storage diseases such as Gaucher's disease. These multiple lesions are termed "xanthoma disseminatum". One reported case is of a 10 year old boy with lytic lesions in the pelvis, femur, and humerus, as well as yellow and brown papules and plaques on the face and trunk. This patient also had polyuria and polydipsia, and was found to have diabetes insipidus. (Khandpur) Radiographically, the lesion occur commonly in the ribs, pelvis, including the sacrum and ilium, or in the epiphysis or diaphysis of tubular bones. These tumors have been reported in the jaw and associated soft tissues. In another report this tumor occurred commonly around the knee.

X-Ray Appearance and Advanced Imaging Findings: 
It has a lytic, loculated appearance with prominent sclerosis of the edges of the lesion. There is no matrix mineralization. The zone of transition of the lesion is narrow. Cortical expansion and soft tissue invasion are rarely seen. The tumor may resemble non-ossifying fibroma, except that the patients are older and have pain, and these lesions have more promenent marginal sclerosis. Some authors have report a periosteal reaction, but others do not. There is prominent marginal sclerosis which may have the appearance of periosteal reaction in lesions that are juxtacortical. CT scan shows a moderately irregular lytic area with an prominent trabecular pattern and surrounding sclerotic bone. On MRI scans, there is central low signal intensity with a surrounding rim of high signal on T1, and more uniform but somewhat varigated high signal intensity on T2 sequences, with the surrounding sclerotic bone having low signal intensity. On bone scan, the lesion has been reported to have no uptake, but the author cannot confirm this.
Laboratory Findings: 
Laboratory studies are not helpful.
Histopathology findings: 
On gross examination, the tumor tissue consists of a mixture of firm but unmineralized yellow-tan tissue and partially hemorrhagic red-brown tissue. The yellow-tan tissue contains predominantly xanthic material. Histologically , the tumor consists of fibroblasts and mononuclear or multinucleated cells that have the appearance of histiocytes. The tumor may contain large areas of "foam cells", lipid-filled cells with abundant vacuolated cytoplasm, interspersed with small fibrovascular septations, as well as masses of cholesterol. No mitotic activity, cellular atypia, or pleomorphism is present. In one review (Bertoni) giant cells were found in 21 of 21 cases, where as other pathologists believe that there are normally no giant cells or an occasional multinuceated giant cell in these tumors. The cells are negative for S100 and positive for anti-human macrophage marker HAM-56, which indicates hystiocyte lineage.
Treatment Options for this Tumor: 
Treatment consists of careful and complete curettage and filling of the defect with graft material, bone cement, or other suitable bone void filler.
Outcomes of Treatment and Prognosis: 
The risk of recurrence is variable depending on which series is consulted. In one series, (Clarke) 3 of 8 cases recurred locally, and two required amputation. In the Bertoni series, none of the 21 cases had local recurrence.
Suggested Reading and Reference: 
Bertoni at al, Am J Clin pathol., 1988;90 377-384 Clarke et al, Am J Surg Pathol., 1985;9:806-815 Macdonald, Arch Pathol Lab Med. 2002;126:599-601 Khandpur et al, Aus J Dermatol., 2003;44:190