大腿部遠位に発生した腱鞘巨細胞腫（tenosynovial giant cell tumor）diffuse-typeの1例

Diffuse-type Tenosynovial Giant Cell Tumor of the Distal Thigh. Case Report

　抄録：腱鞘巨細胞腫（tenosynovial giant cell tumor）のdiffuse-type（以下TGCT-Dと略す）は比較的稀であり，悪性軟部腫瘍との鑑別も困難である．今回，大腿部遠位に発生した巨大なTGCT-Dに広範切除術を施行した1例を経験した．術前の触診で腫瘤は約15×7cm大で表面平滑，弾性硬で可動性はなかった．MRI像ではT1でiso intensity，T2ではまだらにhigh intensityな部分が存在し，ガドリニウムにて造影される巨大な腫瘤であり，臨床的には悪性腫瘍を疑った．しかし，術後の病理所見では，破骨細胞型多核巨細胞や泡沫細胞の集族像を認め，核分裂像は少なく，TGCT-Dと診断した．臨床的にTGCT-Dは悪性軟部腫瘍との鑑別は困難であるが，組織学的に鑑別可能であるため，切除術前に切開生検により診断を確定することが重要である．

　Tenosynovial giant cell tumor, diffuse-type (TGCT-D), is relatively rare, and it is difficult to differentiate from other malignant soft tissue tumors. We report a case of large TGCT-D located in the distal thigh. The tumor was elastic hard, had a smooth surface, and was immobile. It measured approximately 15×7cm. The mass was iso intense on the T1-weighted MR image and partly high intense on the T2-weighted image, and it was enhanced with gadolinium. Based on these findings a malignant tumor was suspected clinically, but histological examination of the surgical specimen revealed clusters of osteoclast-type multinucleated giant cells and foam cells without mitoses, indicating TGCT-D. Since differentiation of TGCT-D from other malignant soft tissue tumors is difficult clinically, preoperative diagnosis by open biopsy is recommended, because the differential diagnosis can be made histologically.