Image Quiz

Destructive Fibular Lesion in a Ten-Year-Old Boy1 (continued)

Answer: Benign fibrous histiocytoma of bone.

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Fig. 1-A
Fig. 1-B
Fig. 1-C
Figs. 1-A and 1-B Anteroposterior (Fig. 1-A) and lateral (Fig. 1-B) radiographs of the left knee, demonstrating a slightly expansile, lytic lesion (arrows) with cortical thinning but without cortical breakthrough or periosteal reaction.
Fig. 1-C Coronal T1-weighted magnetic resonance image showing the expansile involvement of the proximal portion of the fibula (arrows).

Fig. 1-D
Fig. 1-E
Fig. 1-F
Figs. 1-D and 1-E Contrast-enhanced, fat-suppressed sagittal T1-weighted magnetic resonance images. Fig. 1-D shows expansile involvement (arrows) with homogeneous enhancement and without extraosseous extension. Fig. 1-E shows the extent of expansion (arrows) without extraosseous involvement.
Fig. 1-F Fat-suppressed T2-weighted axial magnetic resonance image (white arrows), showing no evidence of edema about the fibula.

Fig. 1-G
Fig. 1-H		 Figs. 1-G and 1-H High-power histologic images. Fig. 1-G demonstrates a benign spindle-cell stroma with moderate cellularity and no atypia. The cells are in storiform pattern (arrows), and a few multinucleated giant cells (block arrows) are present. Fig. 1-H demonstrates the presence of foamy histiocytes (arrows), a characteristic finding in benign fibrous histiocytoma.

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Treatment

Complete curettage of the lesion and packing of the defect with allograft bone.

Discussion

While benign fibrous histiocytoma is a relatively common and well-characterized soft-tissue lesion, it occurs only rarely in bone. Attempts at its classification have created controversy. At one European institution, benign fibrous histiocytoma of bone represented approximately 1% of all benign bone tumors that required an operation1. These benign fibrous bone lesions have been described as variants of more common tumors, calling them adult forms of nonossifying fibromas, regressive forms of giant cell tumors, or benign forms of malignant fibrous histiocytomas2.

The typical presentation of a benign fibrous histiocytoma of bone is a lytic lesion, often with a sclerotic rim that is slightly expansile and moderately painful, in a patient who is older than twenty years of age. It is usually found in long bones, most commonly in the femur and tibia, but can involve the axial skeleton. Although the age of the patient in this report is younger than that of the typical patient with benign fibrous histiocytoma, the lesion has been reported to occur in patients younger than twenty years of age3-9. A more typical scenario can be demonstrated in a case in which a twenty-five-year-old man was referred to the orthopaedic oncology clinic of the senior author (R.D.L.) after several months of having a dull pain in the left knee. Plain radiographs revealed the lesion demonstrated in Fig. 2-A. A magnetic resonance image of the same lesion is presented in Fig. 2-B.


Fig. 2-A
Fig. 2-B		 Fig. 2-A Anteroposterior radiograph of the left knee in a more typical presentation of benign fibrous histiocytoma in a twenty-five-year-old man. The radiograph shows a tibial osteolytic lesion with surrounding sclerosis (arrows) and slight expansion.
Fig. 2-B Sagittal T1-weighted magnetic resonance image of the left tibia of the same patient, demonstrating the expansile lesion (arrows).

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Although benign fibrous histiocytoma most often presents in patients who are older than twenty years, the lesion can occur at any age5,8,10. In children, a benign bone lesion is much more likely to represent a nonossifying fibroma or a metaphyseal cortical fibrous defect rather than a benign fibrous histiocytoma7. Most patients with this tumor describe pain about the site of the lesion even in the absence of a pathologic fracture. In contrast, nonossifying fibromas are typically painless, unless a fracture is already present1,10-13.

Radiographically, benign fibrous histiocytomas of bone usually appear as eccentric focal lytic lesions, usually with a perimeter of sclerosis. While Unni et al.8 stated that benign fibrous histiocytomas most commonly occur in the iliac wing (as was seen in three of their nine patients), Campanacci5 found that they typically occur in long bones, most commonly about the knee (as was seen in eleven of his twenty patients), which is similar to the findings in several other series1,2,6,11,13. Benign fibrous histiocytoma can involve the epiphysis, metaphysis, or diaphysis and may involve the growth plate. The lesion may have a so-called bubbly appearance or show signs of expansion with cortical thinning, but it does not cause periosteal reaction or invade the soft tissue.

Benign fibrous histiocytoma is radiographically differentiated from nonossifying fibroma on the basis of its more aggressive bone destruction, which can be similar to that caused by a giant cell tumor1,6. Nonossifying fibroma usually occurs in patients who are younger than twenty years of age. The tumor typically arises in the metaphysis of long bones, does not show cortical expansion, is small or moderate in size, and does not cross the physis6,12. The use of multiple imaging techniques (radiography, magnetic resonance imaging, angiography, and bone scintigraphy) can also assist in narrowing the differential diagnosis. A benign fibrous histiocytoma typically appears hypovascular on angiography, whereas a giant cell tumor usually appears hypervascular2. Bone scintigraphy shows increased activity in the affected areas1,2. Because the age of our patient was atypical for the appearance of a benign fibrous histiocytoma, the tumor could be radiographically and clinically distinguished from a nonossifying fibroma on the basis of the extent of lesion expansion, pain in the absence of pathologic fracture, and physeal involvement. Although plain radiography suggested that this lesion was an aneurysmal bone cyst, magnetic resonance imaging revealed enhancement within the lesion, suggesting a greater solid component; therefore, chondromyxoid fibroma, osteoblastoma, desmoplastic fibroma, and giant cell tumor were also considered in the differential diagnosis.

The histologic appearance of a benign fibrous histiocytoma is described as a collection of fibroblasts and histiocytes in a storiform pattern, often with foam cells and scattered giant cells (Figs. 1-G and 1-H). Giant cells are a less prominent feature in these lesions than in giant cell tumors, and this subtle difference is important to recognize since both tumors occur in a similar age group. The absence of malignant features, such as abnormal nuclei and atypical mitotic figures, should be noted so that the lesion can be differentiated from a malignant fibrous histiocytoma. The histology of benign fibrous histiocytoma of bone has been reported to be very similar or even "microscopically identical" to that of nonossifying fibroma and metaphyseal fibrous defects, so the final diagnosis greatly depends on the clinical features as well as the radiographic and histologic appearances2,7,13,14. It is important to differentiate these entities because benign fibrous histiocytoma has been associated with a higher recurrence rate and thus requires close follow-up after surgical intervention2,7,13.

The standard treatment for benign fibrous histiocytoma is curettage and bone-grafting, but recurrence has been reported1,5-7,10,11,13. In some instances, a wide excision is performed in an attempt to reduce the risk of recurrence, but even this more aggressive approach does not prevent tumor recurrence7,10. Some authors have suggested the use of phenol or cryotherapy as adjuvant treatment, but the benefits of treating benign fibrous histiocytoma with these substances has not been proven clinically1,4,10.

*Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. One or more of the authors or a member of his or her immediate family received, in any one year, payments or other benefits of less than $10,000 or a commitment or agreement to provide such benefits from a commercial entity (Dr. Lackman is a consultant for Stryker). Also, a commercial entity (Stryker) paid or directed in any one year, or agreed to pay or direct, benefits in excess of $10,000 to fund Dr. King's research fellowship.

References

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2. Hamada T, Ito H, Araki Y, Fujii K, Inoue M, Ishida O. Benign fibrous histiocytoma of the femur: review of three cases. Skeletal Radiol. 1996;25:25-9.
3. Azouz EM. Benign fibrous histiocytoma of the proximal tibial epiphysis in a 12-year-old girl. Skeletal Radiol. 1995;24:375-8.
4. Balasubramanian C, Rajaraman G, Singh CS, Baliga DK. Benign fibrous histiocytoma of the sacrum--diagnostic difficulties facing this rare bone tumor. Pediatr Neurosurg. 2005;41:253-7.
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9. van Giffen NH, van Rhijn LW, van Ooij A, Cornips E, Robben SG, Vermeulen A, Maza E. Benign fibrous histiocytoma of the posterior arch of C1 in a 6-year-old boy: a case report. Spine. 2003;28:E359-63.
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11. Bertoni F, Calderoni P, Bacchini P, Sudanese A, Baldini N, Present D, Campanacci M. Benign fibrous histiocytoma of bone. J Bone Joint Surg Am. 1986;68:1225-30.
12. Campanacci M. Bone and soft tissue tumors. 2nd ed. New York: Springer; 1999: Histiocytic fibroma; p 73-91.
13. Clarke BE, Xipell JM, Thomas DP. Benign fibrous histiocytoma of bone. Am J Surg Pathol. 1985;9:806-15.
14. Roessner A, Immenkamp M, Weidner A, Hobik HP, Grundmann E. Benign fibrous histiocytoma of bone. Light- and electron-microscopic observations. J Cancer Res Clin Oncol. 1981;101:191-202.