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背景.近年,MRI拡散強調像は撮影技術の進歩によって躯幹部にも応用できるようになってきた.今回われわれは再発胸腺腫の診断にMRI拡散強調像が有用であった1例を経験した.症例.30歳代女性.重症筋無力症(IIb型)合併胸腺腫(正岡IVa期)に対して化学療法施行後に手術を施行した.WHO分類のType B3であった.その後,化学放射線療法が施行されたが,初回手術3年9ヵ月後に胸腔内の再発を来し再切除を施行.初回手術5年9ヵ月後に施行したFDG-PET/CTにて傍大動脈領域と右第XI肋間背側にFDGの集積を認め再発と診断した.しかし,FDG-PET/CTでは集積を認めなかったが,MRI拡散強調像で右胸腔内に高信号を呈する小さな病変を他に計5個認め,播種と診断した.傍大動脈領域の再発巣を切除した後,胸腔内の播種病変を完全切除することができた.結論.本症例ではMRI拡散強調像にて小さな再発巣を描出することができ完全切除することができた.今後,本症例の経過観察にMRI拡散強調像が有用であると考えられた.
Background. Recent technological advances in MRI-DWI now allow it to be applied to the whole body. A patient with a recurrent thymoma was accurately diagnosed using MRI-DWI. Case. A 30-year-old woman was given a diagnosis of thymoma (Masaoka's stage IVa) with myasthenia gravis (type IIb) and received induction chemotherapy and underwent an operation. She also received chemoradiation therapy postoperatively. Three years and 9 months later, an intrathoracic recurrence appeared and the lesion was resected. Five years and 9 months after the initial operation, FDG-PET/CT revealed accumulation of FDG in the para-aortic lesion and the posterior side of the right XIth intercostal space. In contrast, MRI-DWI revealed a high intensity of these lesions and 5 other small lesions in the right thoracic cavity, which showed no FDG accumulation in FDG-PET/CT. The lesions were completely resected and all 7 lesions were confirmed to be recurrent thymoma. Conclusion. Small recurrent thymomas could be successfully detected using MRI-DWI, but not FDG-PET/CT. MRI-DWI was therefore considered to be a useful tool for detecting disseminated lesions of thymoma in this case.
