Supplementary Material for: Reactive Intravascular Plasmablastic/Immunoblastic Proliferation in A Patient with Concurrent Gastric MALT Lymphoma and Tuberculosis Potentially Mimicking Aggressive Intravascular Lymphoma: A Rare Case Report

Introduction: Reactive intravascular plasmablastic/immunoblastic proliferation (RIVPIP) is rarely reported. RIVPIP may histologically mimic aggressive intravascular lymphoma, especially in the context of an old patient presenting with concurrent indolent lymphoma and tuberculosis, and easily lead to erroneous diagnosis. Case Presentation: A 79-year-old female presenting with upper abdominal discomfort, weight loss, hypoproteinemia and polyserosal effusions underwent a gastric endoscopy examination. Biopsy revealed that the lamina propria was infiltrated by a large number of uniformly small-sized lymphocytes (CD20+/PAX5+) with lymphoepithelial lesions and epithelioid granuloma. Notably, vascular lumens were filled and distended by abundant large-sized plasmablasts or immunoblasts (CD79α+/MUM1+/CD20-/CD138-/PAX5-/CD30-/Bcl-2-/Bcl-6-/C-myc-). These intravascular large lymphoid cells demonstrated high proliferative activity (Ki67 >80%) without immunoglobulin light chain restriction or EBV association (EBER-ISH negative). Furthermore, PCR revealed monoclonal rearrangements in IgH, IgK and IgL genes. The patient had a history of endoscopic gastric biopsy two months ago. Retrospective analysis of a prior biopsy identified conspicuous caseating necrosis, epithelioid granuloma, multinucleated gaint cells with suspicious positivity for acid-fast staining, highly suggestive of tuberculosis. Based on two biopsy specimens and systemic symptoms, the case was finally diagnosed as gastric MALT lymphoma and tuberculosis with extensive RIVPIP. Conclusion: We present an unusual case of RIVPIP with severe systemic symptoms due to concurrent gastric MALT lymphoma and tuberculosis, emphasizing a potential diagnostic pitfall for clinical pathologists in distinguishing RIVPIP from the aggressive intravascular lymphoma. A comprehensive evaluation of clinical manifestations, pathological morphology, immunophenotype and gene analysis is required to make the precise diagnosis.引言：反应性血管内浆母细胞/免疫母细胞增生（Reactive intravascular plasmablastic/immunoblastic proliferation, RIVPIP）罕见报道。该病变在组织学上可酷似侵袭性血管内淋巴瘤，尤其当老年患者同时合并惰性淋巴瘤与结核病时，极易造成误诊。 病例报告：1例79岁女性因上腹部不适、体重下降、低蛋白血症及多浆膜腔积液接受胃镜检查。活检结果显示，黏膜固有层被大量形态均一的小淋巴细胞（CD20+/PAX5+）浸润，伴淋巴上皮病变及上皮样肉芽肿。值得注意的是，血管腔内被大量大体积浆母细胞或免疫母细胞充盈扩张，其免疫表型为CD79α+/MUM1+/CD20-/CD138-/PAX5-/CD30-/Bcl-2-/Bcl-6-/C-myc-。上述血管内大淋巴样细胞增殖活性极高（Ki67＞80%），无免疫球蛋白轻链限制性表达，且与EB病毒（Epstein-Barr virus, EBV）无关（EBER原位杂交（EBER-ISH）阴性）。进一步聚合酶链式反应（Polymerase Chain Reaction, PCR）检测显示，IgH、IgK及IgL基因存在单克隆重排。患者2个月前曾接受胃镜下胃活检。回顾性分析此前的活检标本，可见显著干酪样坏死、上皮样肉芽肿及多核巨细胞，抗酸染色呈可疑阳性，高度提示结核病。结合两次活检标本及全身症状，最终确诊为胃黏膜相关淋巴组织（mucosa-associated lymphoid tissue, MALT）淋巴瘤合并结核病，并伴广泛RIVPIP。 结论：本文报告1例罕见的RIVPIP病例，该患者因同时合并胃MALT淋巴瘤与结核病而出现严重全身症状，旨在提醒临床病理医师在鉴别RIVPIP与侵袭性血管内淋巴瘤时存在潜在诊断陷阱。临床需综合评估临床表现、病理形态学、免疫表型及基因分析结果，方可实现精准诊断。