大腿遠位に発生したdiffuse-type giant cell tumor（extra-articular form）の2例

Diffuse-type Giant Cell Tumor (Extra-articular Form) of the Distal Thigh. Report of Two Cases

　われわれは大腿遠位に発生したdiffuse-type giant cell tumor（extra-articular form）の2例を報告する．画像上，悪性腫瘍が示唆されたため，両例とも術前に生検を行った．生検組織所見は，単核細胞の増殖と破骨細胞様多核巨細胞，泡沫様細胞を認めたが，多形性や核異型はなかった．免疫組織化学染色でCD68が陽性であった．2例とも術前の生検により確定診断が可能であり，治療方針の決定に有用であった．1例は広範切除，もう1例は辺縁切除を行った．それぞれ術後2年と1年1カ月の時点で再発は認めていない．

　We report two cases of diffuse-type giant cell tumor (D-GCT) (extra-articular form) of the distal thigh. The MRI findings in both cases suggested a malignant soft tissue tumor, and a biopsy was performed. Histological examination showed proliferation of mononuclear cells mixed with multinucleate osteoclast-like giant cells, form cells. There was no nuclear pleomorphism or atypia. Immunohistochemical staining revealed that the mononuclear cells were positive for CD68. Based on these findings, a diagnosis of D-GCT was made. It was difficult to differentiate D-GCT from other malignant soft tissue tumors on the basis of the MRI findings, but the preoperative biopsy was useful in making a definitive diagnosis. Although D-GCT are regarded as benign, the fact that they are locally aggressive neoplasms with significant potential for recurrence makes wide resection preferable. One patient was treated by wide resection and the other by marginal resection. There is no evidence of recurrence in either patient as of 24months and 13months respectively, after surgery.