下顎骨の放射線誘発未分化高等級多形肉腫（悪性線維性組織球腫）：長年の骨髄炎を背景に発生した症例の報告および文献のレビュー

Radiation-induced undifferentiated high-grade pleomorphic sarcoma (malignant fibrous histiocytoma) of the mandible: report of a case arising in the background of long-standing osteomyelitis with a review of the literature.

抄録

44歳女性の右下顎に発生した放射線誘発未分化高等級多形肉腫（UPS）（悪性線維性組織球腫，MFH）の稀な症例を報告する。患者は数年前から下顎の同部位の骨髄炎に悩まされており，19年前に右頸部の悪性リンパ腫に対する放射線治療が原因と考えられた。腫瘍は下顎骨の臼歯部に外植性の浸潤性増殖として出現した。病理組織学的に，腫瘍はVimentin免疫陽性の紡錘形繊維芽細胞の交錯増殖からなり，Ki-67標識スコアの高い奇妙な核を持ち，腫瘍細胞は多形性細胞に混じって縞模様が見られた。放射線照射の既往を考慮し，放射線誘発性MFH/UPSと診断した。顎骨に発生した放射線誘発性UPSは本症例を含めて14例しか報告されておらず，本症例は長年の骨髄炎の経過観察中に発生した初めてのUPSである。

We report a rare case of radiation-induced undifferentiated high-grade pleomorphic sarcoma (UPS) (malignant fibrous histiocytoma, MFH) in the right mandible of a 44-year-old woman. The patient had suffered from osteomyelitis of the same region of the mandible for several years, which was considered to be due to radiotherapy for a malignant lymphoma in her right neck 19 years before. The tumor appeared as an exophytic and invasive growth in the molar region of the mandible. Histopathologically, the tumor consisted of an interlacing proliferation of vimentin-immunopositive spindle-shaped fibroblastic cells with bizarre nuclei with high Ki-67 labeling scores, and tumor cells showed storiform patterns mixed with pleomorphic cells. Taking the history of radiation into consideration, we diagnosed the lesion as radiation-induced MFH/UPS. Including the present case, there have been only 14 documented cases of radiation-induced UPS in the jawbone, and this is the first UPS case arising in the follow-up period of long-standing osteomyelitis.