ALK-positive ( +) large B cell lymphoma (ALK + LBCL) is a rare distinct subtype of diffuse large B cell lymphoma presenting with high stage and aggressive behavior. Although B cell markers such as CD20, CD19, and CD22 are generally negative, plasmacytic markers including CD138, CD38, and MUM1 are positive. T cell markers are negative with rare exceptions. We report an unusual case of ALK1 + LBCL in a 58-year-old man with partial expression of CD3 without other T cell antigen expression. The tissue was evaluated with flow cytometry, immunohistochemistry, fluorescent in situ hybridization, and gene rearrangement studies. Gene rearrangement studies for IGH and TCR gamma were performed. Flow cytometry did not demonstrate any abnormal lymphoid populations. Tissue sectioning shows a malignant plasmacytic large cell neoplasm which expresses CD45 but is negative for CD20, CD79a, and PAX5. Plasmacytic markers CD138 and MUM1 are positive with kappa light chain restriction. Strong granular cytoplasmic expression of ALK is present. FISH showing disrupted ALK supports the diagnosis while MYC, BCL6, and BCL2 are intact. Gene rearrangement studies show coexisting IGH and TCR gamma clones; however, the TCR peak was present within a polyclonal background suggesting the disputed cells are likely only a subset of the T cell population. ALK + LBCL can present with an ambiguous immunophenotype, which warrants the use of multiple B cell, T cell, and plasmacytic antibodies. CD3 expression in this entity is rare and of uncertain clinical significance, but warrants further study.

ALK 阳性 (+) 大 B 细胞淋巴瘤 (ALK + LBCL) 是弥漫性大 B 细胞淋巴瘤的一种罕见的独特亚型，表现为晚期和侵袭性行为。尽管 B 细胞标记物（例如 CD20、CD19 和 CD22）通常呈阴性，但浆细胞标记物（包括 CD138、CD38 和 MUM1）却呈阳性。除极少数例外，T 细胞标记均为阴性。我们报告了一名 58 岁男性的 ALK1 + LBCL 罕见病例，其部分表达 CD3，但不表达其他 T 细胞抗原。通过流式细胞术、免疫组织化学、荧光原位杂交和基因重排研究对组织进行评估。进行了IGH和TCR gamma的基因重排研究。流式细胞术没有显示任何异常的淋巴细胞群。组织切片显示恶性浆细胞大细胞肿瘤，表达 CD45，但 CD20、CD79a 和 PAX5 呈阴性。浆细胞标记 CD138 和 MUM1 呈阳性，且具有 kappa 轻链限制。存在 ALK 的强颗粒状细胞质表达。 FISH 显示 ALK 中断支持诊断，而MYC、BCL6和BCL2完好。基因重排研究显示IGH和TCR γ 克隆共存；然而，TCR峰值出现在多克隆背景中，表明有争议的细胞可能只是 T 细胞群的一个子集。 ALK + LBCL 可呈现不明确的免疫表型，这需要使用多种 B 细胞、T 细胞和浆细胞抗体。 CD3 在该实体中的表达很少见，临床意义不确定，但值得进一步研究。