Indolent T lymphoblastic proliferations have been reported rarely in extramedullary and extrathymic tissues. Recent work has identified these indolent T lymphoblast populations to be mostly CD4+/CD8+ (characterized by immunohistochemistry), with only limited immunophenotypic evaluation of these populations by flow cytometry (FC). We retrospectively reviewed our institutional FC archives and identified 12 samples from 10 patients with incidental T lymphoblastic populations. Samples were characterized with respect to expression of T-cell antigens, CD45, TdT, CD1a, and T/NK antigens, and light scatter properties. Overall, the proportion of T lymphoblasts was small (range 0.01-8.8% of white cells; mean, 1.7%). Histologic correlation showed scattered immature T lymphoblasts in samples without overt distortion of underlying architecture. T lymphoblasts were identified most frequently in association with Castleman disease (four) or tissues with Castleman features (four), marginal zone B-cell lymphoma (one), or tissue with reactive/atypical changes (three cases). Although three cases were composed predominantly of CD4+/CD8+ T cells, the majority of cases in our cohort (eight) included a major subset of CD4-/CD8- T lymphoblasts by FC (one case CD8+/CD4-), which has not been described previously. There was no evidence of subsequent progression to T lymphoblastic leukemia. Incidental, indolent T lymphoblastic proliferations may be detected by clinical FC. In contrast to reports, we find that these proliferations in clinical samples may contain not only CD4+/CD8+ immature T cells but also CD4-/CD8- immature T cells, expanding the immunophenotypic spectrum of this entity.

中文翻译：

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偶发性惰性T淋巴细胞增殖的流式细胞仪特征。

在髓外和胸腺外组织中很少有惰性T淋巴细胞增殖的报道。最近的工作已确定这些惰性T淋巴母细胞群体主要为CD4 + / CD8 +（通过免疫组织化学表征），仅通过流式细胞术（FC）对这些群体进行有限的免疫表型评估。我们回顾性地回顾了我们的机构FC档案，从10例T淋巴细胞伴生人群中鉴定了12个样本。关于T细胞抗原，CD45，TdT，CD1a和T / NK抗原的表达以及光散射特性对样品进行表征。总体而言，T淋巴母细胞的比例很小（范围为白细胞的0.01-8.8％；平均值为1.7％）。组织学相关性显示样品中散布的未成熟T淋巴母细胞没有明显的基础结构扭曲。T淋巴母细胞最常与Castleman病（四个）或具有Castleman特征的组织（四个），边缘区B细胞淋巴瘤（一个）或具有反应性/非典型性改变的组织（三例）相关联。尽管3例病例主要由CD4 + / CD8 + T细胞组成，但我们队列中的大多数病例（8例）包括FC的CD4- / CD8-T淋巴母细胞的主要子集（1例CD8 + / CD4-），但并非如此。如前所述。没有证据表明随后发展为T淋巴细胞白血病。偶然的，惰性的T淋巴母细胞增生可通过临床FC检测到。与报道相反，我们发现临床样品中的这些增殖可能不仅包含CD4 + / CD8 +未成熟T细胞，而且还包含CD4- / CD8-未成熟T细胞，从而扩大了该实体的免疫表型谱。