A case report of skeletal muscle metastasis of renal cell carcinoma effectively treated with interferon-alpha

74歳女.左腎細胞癌の診断を受け根治的左腎摘除術を行った.術後6年で右背部の腫瘤を自覚し, その後左大腿部の疼痛を伴う腫瘤を訴えた.針生検により病理組織学的に腎細胞癌の左大内転筋内転移と診断された.胸部CTでは肋骨に骨破壊を伴う腫瘤を認め, 肺野では多発性結節状陰影を認めた.以上の腎細胞癌転移に対しnIFN-α筋注を行った.投与約1週間後より左大腿部の疼痛は軽快傾向となり, 同部位の腫瘤も縮小傾向を示した.投与開始2ヵ月半後には大腿部の腫瘤は触知不能となった.大腿部CTおよびIV-DSAで投与開始7ヵ月後には転移巣は50%以上縮小した.しかし10ヵ月後より増大傾向を示し, 13ヵ月後のCTでPDと判定した.肋骨転移は投与開始7ヵ月後には転移巣は40%の縮小を認めたが, 14ヵ月後には増大傾向を示した.肺野転移は投与開始7ヵ月後には小さな転移巣は消失したが, 最大の転移巣が増大傾向を示した.14ヵ月後にはさらに増大傾向を示したが, 新病変は認めなかった.投与開始後23ヵ月後の現在, 外来で継続加療中である
The skeletal muscle is a very rare site of metastasis in renal cell carcinoma. We report the third case of skeletal muscle metastasis of renal cell carcinoma effectively treated with interferon-alpha. The patient was a 74-year-old woman who had undergone radical nephrectomy on the left side for renal cell carcinoma on April 23, 1990, and had been observed as an outpatient. In June 1997, she was admitted with a diagnosis of metastasis in the left great adductor muscle and right sixth rib, as well as multiple lung metastasis. The metastatic lesion in the great adductor muscle decreased in size by more than 50% following concomitant intramuscular administration of natural interferon-alpha (nIFN-alpha). In the other metastatic lesions, nIFN-alpha-sensitive and resistant metastatic foci were intermingled. Thus, the primary focus in the present study was presumably composed of several clones with different sensitivities to nIFN-alpha.