長期生存を得た肋骨原発骨内分化型骨肉腫の1切除例

摘要

背景．骨内分化型骨肉腫は，長期の臨床経過をたどる低悪性度骨腫瘍として最近知られるようになった骨肉腫の1亜型である．その肋骨原発は非常に稀であり，今回報告する．症例．45歳男性，38歳時（昭和63年）より胸部X線写真上，右胸壁の異常影を指摘されていた．平成7年4月近医を再受診した際，腫瘤影の増大が認められ，同年6月当科紹介となった．胸部X線写真上では，右胸壁より上肺野に突出する4cm大の辺縁整の腫瘤影を認めた．胸部CTでは右第4肋骨に内部不均一な腫瘍を認めた．悪性骨腫瘍の可能性を考慮し同年7月18日手術を施行，右第4肋骨の部分切除および上下肋間筋の合併切除を施行した．術後の病理組織検査にて右第4肋骨原発の骨内分化型骨肉腫と診断された．術後は化学療法や放射線療法を施行しなかったが，約7年経過した現在，再発なく生存中である．結論．骨内分化型骨肉腫の組織診断は困難であるが，本例では組織学的に骨周囲組織への浸潤像が　 fibrous dysplasiaとの重要な鑑別点となった．さらに，腫瘍を完全切除できたことが，初回発見時より14年という長期生存に寄与したものと考えられた．Background. Intraosseous well-differentiated osteosarcomas (IWDOS) are rare and commonly originate in the extremities as conventional osteosarcoma. We reported a very rare case of IWDOS of the right rib. Case. A 45-year-old man was admitted to our hospital because of an abnormal shadow on chest roentgenogram in April, 1995. He had once been examined at another hospital because of abnormal findings on the chest X-ray film detected by a mass screening program in November, 1988. His chest X-ray film showed a tumor shadow (4.0 * 5.0 cm) on the chest wall protruding into the upper right lung field. The tumor shadow had slightly enlarged in size compared to previous ex-aminations. Chest CT revealed a heterogeneous tumor with calcification fixed on the 4th rib, but which did not infiltrate the surrounding tissues. Bone scintigram showed an abnormal accumulation at the site of the chest wall tumor. Because of the possibility of malignancy, an en bloc excision of the tumor was performed, including the right 4th rib and surrounding intercostal muscles with a sufficient surgical margin on July 18,1995. The histologic examination revealed IWDOS of the right 4th rib. The patient underwent no additional adjuvant chemotherapy nor radiation therapy postopera-tively and is now alive and well, without any sign of recurrence, 7 years after the operation.