梨状筋症候群を呈した骨外性骨肉腫の1例

Piriformis Syndrome Caused by Extraosseous Osteosarcoma : Case Report

　抄録：放射線照射を施行後，梨状筋症候群を引き起こした骨外性骨肉腫の1例を経験したので報告する．症例は49歳，女性．既往歴として，16年前に子宮頚癌の診断で，子宮と卵巣の全摘出術および，放射線照射を50Gyの用量で受けていた．3カ月前から左下肢痛を自覚し，増強したため当科を初診した．初診時左坐骨神経障害を認め，X線，CT検査にて，左梨状筋部に造骨性腫瘍を認めた．腫瘍摘出術を施行し，病理組織診断は骨外性骨肉腫であった．当症例は，放射線照射後，比較的長期の潜伏期間を経て，坐骨神経障害として発症した骨外性骨肉腫と考えられる．その発生部位が，梨状筋前方軟部組織から坐骨神経にかけて発生していたため，梨状筋症候群を呈したものと考えられ極めて稀な症例である．

　We experienced a case of extraosseous osteosarcoma in an irradiated area, which showed the same symptom that piriformis syndrome revealed. This is a case report of a patient, forty-nine years old female. She was given radiation therapy in total dose of 50 Gy after total removal of ovarium and uterus with a diagnosis of the uterine cervix. She complained of pain at the lower extremity from early in January, 2002. Because of increase in pain, she consulted Higashiosaka City General Hospital. On examination, sciatic nerve disturbance was shown, X-ray and computed tomography showed ossification on the portion of the piriformis muscle. Removal of the tumor was done, and the pathological diagnosis as extraosseous osteosarcoma. It is considered that this present case is classified into radiation-induced extraosseous osteosarcoma, which was arisen after a relatively long, silent latent period since radiation was followed. Because it developed in a cartridge tissue in front of the piriformis muscle and infiltrated into the sciatic nerve, it is considered that this case is extremely rare as the case that revealed piriformis syndrome.