Histological and Molecular Evidence of Synovial Sarcoma of Bone. A Case Report*

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Synovial sarcoma is a clinically and morphologically well defined soft-tissue tumor that occurs predominantly in the extremities of adolescents and young adults. It tends to arise in the vicinity of large joints, especially the knee8. This tumor was designated synovial sarcoma because of its anatomical location and its histological resemblance to normal synovial tissue. However, we do not believe that there is any convincing evidence that synovial sarcoma always originates from synovial tissue. It is possible that the lesion sometimes arises from primitive mesenchymal cells rather than from preformed synovial cells; therefore, the development of synovial sarcoma is no longer thought to require the presence of preexisting synovial tissue. To the best of our knowledge, there have been no reports of synovial sarcoma arising in bone.The reciprocal translocation t(X;18)(p11.2;q11.2) was noted in all twenty-two reported cases of synovial sarcoma that have been studied cytogenetically5,18. This translocation is considered to be specific to this tumor. Cloning of the DNA adjacent to the breakpoints of the translocation t(X;18) has shown2 that this translocation results in fusion of the SYT gene at 18q11.2 to either of two genes, SSX1 or SSX2, at Xp11.2. This rearranged configuration of DNA is transcribed to messenger RNA and is called a chimeric SYT-SSX transcript. A chimeric SYT-SSX transcript does not occur normally and thus provides a specific marker for synovial sarcoma that can be detected with reverse transcriptase-polymerase chain-reaction testing.We describe the case of a patient who had synovial sarcoma of bone that was verified by the detection of a chimeric SYT-SSX transcript.Case ReportA sixty-seven-year-old man had a four-month history of pain in the right wrist when he was first seen by us. Physical examination revealed moderate swelling and a restricted range of motion of the wrist (30 degrees of flexion, 15 degrees of extension, -5 degrees of radial deviation, 15 degrees of ulnar deviation, 50 degrees of pronation, and 30 degrees of supination). The pertinent laboratory data, including a complete blood-cell count and blood-chemistry levels, were normal except for a slight increase in the number of white blood cells (9600 per cubic millimeter [9.6 x 109 per liter]; normal value, 3900 to 9200 per cubic millimeter [3.9 to 9.2 x 109 per liter]) and in the level of C-reactive protein (3.3 milligrams per deciliter [0.33 milligram per liter]; normal value, less than 0.1 milligram per deciliter [0.01 milligram per liter]). A roentgenogram showed a radiolucent lesion located centrally in the medullary bone of the juxta-articular and metaphyseal portions of the radius. The indistinct margin between the tumor and the normal bone revealed the invasive nature of the tumor (Fig. 1). Although magnetic resonance imaging showed expansion of the tumor to the surrounding soft tissue, no adjacent soft-tissue component was apparent (Fig. 2). No abnormal uptake of technetium-99m methylene diphosphonate was found except in the area of the lesion of the right radius. An incisional biopsy was performed through the dorsal aspect of the tumor, and two specimens, each approximately five by five by five millimeters in size, were obtained. The pathological diagnosis was spindle-cell sarcoma. Preoperative neoadjuvant chemotherapy, including intra-arterial infusion of cis-diammine-dichloroplatinum (100 milligrams) and systemic administration of pirarubicin (two doses of forty milligrams each), was given. A wide resection was performed; the resected specimen, which included the tumor and adjacent normal bone, was nine centimeters long. The radius was reconstructed with a fibular graft. Eight months after the resection, pulmonary metastases were detected on plain roentgenograms.

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