浆细胞样树突状细胞肿瘤（BPDCN）是一种罕见的造血系统恶性肿瘤，起源于浆细胞样树突状细胞的前体细胞。异基因造血干细胞移植（HSCT）通常被认为是治疗BPDCN患者以获得持久缓解的方式。移植后淋巴增殖性疾病（PTLD）是一组在固体器官移植（SOT）或HSCT后外源性免疫抑制情况下涉及异常淋巴细胞增殖的疾患。在此，我们报道了一名BPDCN患者，在异基因HSCT后患有PTLD。一名66岁男性患者被诊断为BPDCN，经脾切除后经病理检查证实。手术后的18F-氟脱氧葡萄糖正电子发射计算机断层扫描（18F-FDG PET/CT）显示左颊、淋巴结和骨髓内存在多发18F-FDG亲和性病灶。患者进行了化疗，随后进行了异基因HSCT和免疫抑制治疗。HSCT后4个月，患者出现间歇性发热、反复淋巴结肿大，并伴有血清和淋巴细胞中Epstein-Barr病毒（EBV）DNA逐渐升高。再次进行18F-FDG PET/CT发现多个新出现的增大的18F-FDG亲和性淋巴结，而之前的代谢过剩病灶全部消失。肠系膜淋巴结的病理学证实了单形性PTLD（弥漫性大B细胞淋巴瘤）。随后停止了免疫抑制药物，并进行了两个周期的利妥昔单抗治疗，随访CT扫描显示完全缓解。当BPDCN患者在异基因HSCT和免疫抑制治疗后出现新的增大淋巴结时，应考虑到PTLD的可能性。 18F-FDG PET / CT可以提供额外的证据，支持或否定PTLD的怀疑，并提示活检可及的病灶。 Copyright © 2023 陈，张，马，高，傅和刘。

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an extremely rare hematopoietic malignancy, which originating from precursors of plasmacytoid dendritic cells. Allogeneic hematopoietic stem cell transplantation (HSCT) is normally considered in the treatment of BPDCN patients to acquire sustained remission. Post-transplant lymphoproliferative disorder (PTLD) is a group of conditions involving abnormal lymphoid cells proliferation in the context of extrinsic immunosuppression after solid organ transplantation (SOT) or HSCT. Herein, we report a patient with BPDCN, who suffered from PTLD after allogeneic HSCT.A 66-year-old man was diagnosed with BPDCN, confirmed by pathologic examination after splenectomy. The post-surgery 18F-fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography (18F-FDG PET/CT) showed multifocal 18F-FDG avidity in the left cheek, lymph nodes and bone marrow. The patient started chemotherapy, followed by allogeneic HSCT and immunosuppressive therapy. Four months after the HSCT, the patient developed intermittent fever and recurrent lymphadenopathy, accompanied with progressively elevated Epstein-Barr virus (EBV)-DNA both in serum and lymphocytes. 18F-FDG PET/CT was performed again and found multiple new enlarged 18F-FDG-avid lymph nodes, while the previous hypermetabolic lesions all disappeared. The pathology of mesenteric lymph node indicated a monomorphic PTLD (diffuse large B-cell lymphoma). Then the immunosuppressive medications were stopped and two cycles of Rituximab were given, and the follow-up CT scan indicated a complete response.When patients with BPDCN recurred new enlarged lymph nodes after allogeneic HSCT and immunosuppressive therapy, PTLD should be taken into consideration. 18F-FDG PET/CT may provide additional evidence for supporting or refuting the suspicion of PTLD, and suggest lesions accessible for biopsy.Copyright © 2023 Chen, Zhang, Ma, Gao, Fu and Liu.