胃MALTリンパ腫の脳転移と考えられた1例

A Case of CNS Metastasis from Gastric MALT Lymphoma

Ⅰ．はじめに

　中枢神経悪性リンパ腫は脳腫瘍のうち2.9％を占めるが近年増加傾向にあり¹⁾，全身性リンパ腫からの転移よりも原発性のほうが多いと報告されている²⁾．中枢神経悪性リンパ腫の多くはdiffuse large B-cell lymphoma（DLBCL）であり，他の組織型は稀である．MALT（mucosa-associated lymphoid tissue）リンパ腫は胃や腸などのMALT臓器に発生し，通常長期間発生臓器に限局し，緩除な経過を辿る低悪性度の非ホジキンB細胞リンパ腫である．MALTリンパ腫発生の原因の一部として感染症が関与していると考えられている．今回われわれは，胃MALTリンパ腫の脳転移と考えられた稀な症例を経験したので，若干の文献的考察を加えて報告する．

　Recently, the incidence of primary CNS lymphoma (PCNSL) is increasing. Metastatic CNS lymphoma occurs much less than PCNSL. We report the case of a 53-year-old man who presented with CNS metastasis from gastric mucosa-associated lymphoid tissue (MALT) lymphoma. The symptoms at the time of diagnosis were dizziness and aphasia. MRI revealed a left parietal lobe tumor with a large peritumoral edema. About 4 years ago, he had suffered from gastric MALT lymphoma with a high grade component. Eradication of Helicobacter pylori led to remission of the disease 18 months after the treatment. From his past history, the brain tumor was suspected of being a metastatic lymphoma. Stereotactic biopsy revealed diffuse large B-cell lymhoma. Histopathological findings including lymphocytic subsets were almost identical between the primary gastric MALT lymphoma and metastatic brain lymphoma. Complete remission was obtained by repeated high-dose methotrexate chemotherapy. There has been no recurrence for 5 years without additional therapy. This case is probably the first report of CNS metastasis from gastric MALT lymphoma.