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Osteosarcoma at the Site of a Previously Treated

Aneurysmal Bone CystA CASE REPORT

BY CHIA-CHEN HSU, MD, JUN-WEN WANG, MD, CHENG-HUA HUANG, MD, AND WEI-JEN CHEN, MD

Investigation performed at Chang Gung Memorial Hospital at Kaohsiung, Taiwan, Republic of China

neurysmal bone cyst is an expansile, destructive, hem-orrhagic, non-neoplastic lesion that is thought to repre-sent a benign reactive vascular process1-4. These lesions

have been designated as either primary or secondary, with thelatter term used when histological evaluation indicates a coex-isting lesion, which can be either benign or malignant5,6.

Occasionally, telangiectatic osteosarcomas have been mis-diagnosed as aneurysmal bone cysts7-9, but the true nature of themalignant tumors usually became apparent after rapid progres-sion or recurrence7. Like other benign tumors, aneurysmal bonecysts have been reported to have undergone malignant transfor-mation, although most of the transformations were induced byirradiation7,10,11. In a review of the literature, only two well-docu-mented reports of malignant transformation of an aneurysmalbone cyst without a history of irradiation were found. Onetransformation was to a malignant fibrous histiocytoma, andthe other was to an osteosarcoma7,12.

The purpose of this case report is to describe a patient inwhom an osteosarcoma developed at the site of an aneurysmalbone cyst that had been treated with curettage and bone-graftingsix years earlier. The patient was informed that data concern-ing the case would be submitted for publication.

Case Reportnineteen-year-old man was treated at another hospital inJuly 1993 because of painful swelling of the right leg of

four months’ duration. Radiographs of the tibia made at thattime showed a well-defined intracortical radiolucent lesion inthe proximal part of the tibia (Fig. 1). On physical examina-tion, the patient had a tender bulging mass measuring 5 × 2 ×2 cm in the proximal part of the right leg. A technetium-99mwhole-body bone scan revealed a focal area of increased up-take of radioactivity involving the proximal third of the righttibial shaft with some cold areas in it. No other areas of abnor-mal uptake of radioactivity were revealed on the scan. Com-puted tomography of the right tibia showed a radiolucentlesion and fluid-fluid level in the cavity. The anterior tibialcortex was quite thin.

The patient underwent surgery on July 14, 1993. An ante-rior cortical window was made to explore the tibial lesion, and alarge amount of blood was found in the cystic cavity. Extensive,

meticulous curettage and burring of the margins of the lesionwere performed. Phenol was then applied. The defect was re-constructed with a strut fibular allograft and autogenous iliacbone graft. Histological examination of the surgical specimenrevealed variously sized spaces filled with blood with a wallcomposed of mononuclear stromal cells and giant cells (Figs. 2-A and 2-B). The pathologic diagnosis was aneurysmal bone cyst.

No other adjuvant treatment was given, and the surgi-cal wound healed well. Regular follow-up until 1998 disclosed

A

A

Fig. 1

Lateral and anteroposterior radiographs showing a bone cyst in the

proximal part of the right tibia.

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no clinical or radiographic evidence of recurrence. In March1999, the patient noted an enlarging painful mass at the previ-ous surgical site. Radiographs revealed a recurrent osteolyticlesion in the tibia. This time, the lesion broke through the an-terior cortex of the tibia with sunburst periosteal reaction andsoft-tissue extension (Fig. 3). The patient was referred to ourinstitute in May 1999, where an open biopsy was performed.Histological examination revealed a proliferation of neoplasticosteoblasts with irregular hyperchromatic nuclei diagnostic ofosteosarcoma (Fig. 4).

The patient received four courses of preoperative chemo-

therapy, consisting of intravenous Adriamycin (doxorubicin)and intra-arterial cisplatin, from June 3, 1999, to August 26,1999. On September 21, 1999, a wide resection of the tumorwas performed, after which the skeletal defect was recon-structed with an intercalary allograft and autogenous iliac bonegraft and fixed with an interlocking nail and a buttress plate. Alocal gastrocnemius flap and split-thickness skin grafts wereused by a plastic surgeon to cover the soft-tissue defect. The his-tological examination of the surgical specimen showed 95% tu-mor necrosis. The patient was discharged on October 2, 1999,and he received two more courses of chemotherapy from Octo-

Fig. 2-B

Fig. 2-A

Figs. 2-A and 2-B Photomicrographs of

the aneurysmal bone cyst. Fig. 2-A Low-

magnification image showing a hypocellular,

hemorrhagic cystic space with deposits of del-

icate woven bone in the cyst wall (hematoxylin

and eosin, ×40).

High-power image showing blood spaces sepa-

rated by fibrous stroma containing mono-

nuclear cells (hematoxylin and eosin, ×200).

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ber 13, 1999, to November 19, 1999.Healing of the intercalary allograft to the host bone was

noted seven months after the surgery. At the latest follow-upexamination, in October 2003, the patient was alive with no

evidence of disease and had excellent function of the right legaccording to the functional rating system of Enneking et al.(Fig. 5)13.

Discussionneurysmal bone cyst is a benign lesion that usually occursduring the first three decades of life. Many benign or

malignant tumors of bone can be associated with aneurysmalbone cysts. Sarcomatous changes of an aneurysmal bone cysthave been reported; however, most of those developed after ra-diation treatment7,10,11 and some had actually been overlookedat the time of the initial treatment7.

In our patient, the osteosarcoma may have been missed atthe first operation, may have arisen de novo at the same site, ormay have resulted from spontaneous malignant transforma-tion of the aneurysmal bone cyst. It is unlikely that the diagno-sis of osteosarcoma was missed in our patient initially, for tworeasons. First, the patient had complete excision of the lesion,and all of the tissues were examined histologically. At the initialexamination and on review of the slides after the diagnosis ofosteosarcoma was made, there was no evidence of malignancy;only an aneurysmal bone cyst was seen. Second, the patient hada long disease-free period (approximately six years) before theosteolytic lesion occurred at the previous surgical site eventhough he had not received any adjuvant radiotherapy or che-motherapy after the initial treatment of the aneurysmal bonecyst. If the osteosarcoma had been missed at the initial treat-ment, then rapid progression would be expected14-16. Finally, itmay be argued that the tumor in our patient was a low-gradeaneurysmal bone cyst-like osteosarcoma, the histological fea-tures of which totally mimic those of an aneurysmal bone cyst.Adler17 as well as Reed and Rothenberg18 described this possibil-ity in their patients. However, this rare form of osteosarcomausually affects older patients, and the radiographic and histo-

A

Fig. 3

Anteroposterior and lateral radiographs demonstrating an osteolytic lesion

with a sunburst periosteal reaction of the proximal part of the right tibia.

Fig. 4

Photomicrograph showing features of osteo-

blastic osteosarcoma with proliferation of neo-

plastic osteoblasts and focal osteoid formation

(hematoxylin and eosin, ×100).

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logical findings in the later-resected specimen from our patientwere not suggestive of such an entity.

The long disease-free period between the treatment of theaneurysmal bone cyst and the diagnosis of osteosarcoma is con-sistent with either malignant transformation of the aneurysmalbone cyst or de novo change at the same site. We are aware ofonly two well-documented reports of malignant transforma-tion of aneurysmal bone cysts without radiation treatment7,12.

One of the transformations was to a pleomorphic osteosarcomaof the distal part of the tibia in a patient who had been treatedfor the bone cyst three years earlier7, and the other was to a ma-lignant fibrous histiocytoma of the distal part of the femur in apatient who had been treated for the bone cyst twelve yearsearlier12. To our knowledge, our case report might be the secondreport of malignant transformation of an aneurysmal bone cystto an osteosarcoma. Compared with the similar case reportedby Kyriakos and Hardy7, our patient had a longer interval fromthe initial symptoms of the aneurysmal bone cyst to the devel-opment of an osteosarcoma (six years compared with four yearsand two months). In a review of the literature, we found no re-ports of phenol therapy promoting the development of an os-teosarcoma in the host bone. On the basis of the clinical,radiographic, and histological features of our patient, we con-cluded that the original aneurysmal bone cyst underwent ma-lignant transformation. �

NOTE: The authors gratefully acknowledge Hsin-Nung Shih, MD, for providing the original infor-mation on this patient.

Chia-Chen Hsu, MDJun-Wen Wang, MDCheng-Hua Huang, MDWei-Jen Chen, MDDepartments of Orthopaedic Surgery (C.-C.H. and J.-W.W.), Hematol-ogy and Oncology (C.-H.H.), and Pathology (W.-J.C.), Chang Gung Memorial Hospital, 123, Ta Pei Road, Niao Sung Hsiang, Kaohsiung Hsien, 83305 Taiwan, Republic of China. E-mail address for J.-W. Wang: lee415@adm.cgmh.org.tw

The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive pay-ments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or di-rected, or agreed to pay or direct, any benefits to any research fund, foun-dation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

doi:10.2106/JBJS.C.01625

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Fig. 5

Anteroposterior and lateral radiographs made four years after the sur-

gery, showing good healing of the intercalary allograft to the host bone

without evidence of tumor recurrence.