骨原発平滑筋肉腫の1例

Primary Leiomyosarcoma of Bone. Case Report

　稀な骨原発平滑筋肉腫の1例を報告した．症例は74歳の女性．下腿の疼痛を主訴に来院した．血液検査では腫瘍マーカーを含めて異常所見を認めなかった．単純X線像では，比較的境界明瞭な骨透亮像を認めた．骨シンチグラムでは，ドーナツ状の異常集積像を認め，MRIにてT1で低輝度，T2で高輝度，ガドリニウムで増強される所見が，ほぼ骨内に限局してみられた．病理組織診断では紡錘形細胞肉腫の形態を示し，免疫染色でsmooth muscle actinが陽性になったことから，平滑筋肉腫と診断した．広範囲切除術および腫瘍用人工関節での再建術を行った．膝関節伸展機構は，腓腹筋の前方移行部に膝蓋腱を縫着し再建した．術後1年の現在，無病生存中であり，機能的にも満足している．骨原発平滑筋肉腫は，軟部原発や子宮・腸管からの転移性肉腫との鑑別が必要であるが，稀に存在するので，その存在を念頭に置く必要がある．

　A case of primary leiomyosarcoma of the proximal tibia is reported. No abnormal findings were detected in the blood examination, including tumor marker levels. A plain radiograph, MRI scan, and bone scintigrams revealed non-specific evidence of malignancy in the left proximal tibia. Microscopic examination showed spindle cell sarcoma with positive staining for smooth muscle actin, and the histological diagnosis was leiomyosarcoma. The tumor was widely resected, and reconstruction was with an HMRS tumor prosthesis. The extensor mechanism of the knee joint was covered with reversed gastrocnemius and reserved patella tendon. No evidence of recurrence or metastasis has been detected one year after the operation. Primary leiomyosarcoma is uncommon, and must be differentiated from its counterpart of soft tissue origin and from metastases from internal organs, such as the uterus and the intestine.