一名78岁男性患者因白细胞增多入院。该患者无症状且无淋巴结肿大。外周血流式细胞术显示出一种介于中等到大型、具有网状结构的异常B细胞淋巴瘤。正电子发射断层扫描/计算机断层扫描显示右眶、骨髓和脾脏异常摄取。我们在提取自右眶和骨髓的组织上进行了免疫染色和荧光原位杂交试验，结果显示为黏膜相关淋巴组织（MALT）淋巴瘤。对右眶肿块和骨髓进行的免疫球蛋白重链重排的聚合酶链反应分析表明它们是相同的克隆。根据这些综合结果，确诊为白血病期MALT淋巴瘤，累及骨髓、外周血、右眶和脾脏。这是一例罕见的白血病期MALT淋巴瘤病例。© 2023. 日本血液学会。

A 78-year-old man presenting with leukocytosis was admitted to our hospital. The patient was asymptomatic and showed no lymphadenopathy. Peripheral blood flow cytometry revealed a leukemic-phase B-cell lymphoma with medium-to-large abnormal cells with reticulum. Positron emission tomography/computed tomography revealed abnormal uptake in the right orbit, bone marrow, and spleen. We performed immunological staining and fluorescence in situ hybridization on tissues extracted from the right orbit and bone marrow, which led to the diagnosis of mucosa-associated lymphoid tissue (MALT) lymphoma. Polymerase chain reaction analysis of immunoglobulin heavy chain rearrangements in the right orbital mass and bone marrow suggested that they were identical clones. Based on these collective findings, the diagnosis of leukemic-phase MALT lymphoma was confirmed, with sites of involvement including the bone marrow, peripheral blood, right orbit, and spleen. This is a highly rare case of leukemic MALT lymphoma.© 2023. Japanese Society of Hematology.