A 60-year-old male presented with spontaneous hematomas and cervical adenopathy. Laboratory workup revealed hemoglobin 12.3 g/dL, platelet 56 × 10⁹/L, and leukocyte 14.7 × 10⁹/L. The automated cell counter (Sysmex XN) reported 9% neutrophils (1.32 × 10⁹/L) and 86% lymphocytes (12.6 × 10⁹/L), suggestive of a lymphoproliferative disorder. Blood smear showed atypical lymphoid cells with normal size, mature chromatin, and scant cytoplasm Figure 1 (Panel A), while numerous lysed cells were also observed (Panel B). About 10% of these cells displayed cytoplasmic vacuoles, occasionally coalescing, and 10% appeared larger with grayish cytoplasm (Panel C and D). Due to the apparent lymphocytosis, flow cytometry immunophenotyping was performed (Navios EX, Beckman-Coulter). Surprisingly, 62% of the leukocytes consisted of a CD45+low blastic population. These cells were negative for common lymphoid (CD19/CD20/CD22/CD24/cCD79a/CD3/CD5/CD8/CD10) and myeloid antigens (CD34/CD38/CD13/CD14/CD42b/CD61/CD64/CD65/CD117/cMPO), but were positive for CD4(weak)/CD56/CD123(strong)/HLA-DR(strong)/CD33 (Panel E and F). A cutaneous lesion was found on the patient's back, and bone marrow aspiration confirmed 82% of the same population with additional phenotypic markers indicative of pDC lineage (CD303+weak/CD304+/cTCL1+/BadLamp+), supporting the diagnosis of Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN). The neurological examination was normal, and cerebrospinal involvement was inconclusive due to hemorrhagic cerebrospinal fluid samples. Furthermore, the mutational profile performed on bone marrow aspirate was consistent with BPDCN, revealing mutations in TET2, ASXL1, and NF1, as well as a subclonal NRAS mutation and deletions in the IKZF1 and ETV6 loci.

BPDCN is a rare hematologic malignancy, with diverse morphological presentations. While the classic blastic morphology, often exhibiting “pearl necklace” cytoplasmic appearances and “hand-mirror-like” projections, is the most common presentation, this case displayed an unusual morphology dominated by pseudo-lymphoid cells. Although a subset of pseudo-lymphoid cells is commonly observed in BPDCN, this case was remarkable in that nearly all cells exhibited this distinctive morphology. Such atypical presentation can be deceptive, initially mimicking lymphoid malignancies. Here, the immunophenotypic profile was crucial in establishing the accurate diagnosis.

一名 60 岁男性出现自发性血肿和颈部淋巴结肿大。实验室检查显示血红蛋白 12.3 g/dL，血小板 56 × 10⁹/L，白细胞 14.7 × 10⁹/L。自动细胞计数仪 （Sysmex XN） 报告了 9% 的中性粒细胞 （1.32 × 10⁹/L） 和 86% 的淋巴细胞 （12.6 × 10⁹/L），提示淋巴增生性疾病。血涂片显示非典型淋巴细胞，大小正常，染色质成熟，细胞质稀少 图 1 （图 A），同时还观察到大量裂解细胞 （图 B）。这些细胞中约有 10% 显示细胞质液泡，偶尔聚结，10% 的细胞质呈灰色（图 C 和 D）。由于明显的淋巴细胞增多，进行了流式细胞术免疫表型分析 （Navios EX， Beckman-Coulter）。令人惊讶的是，62% 的白细胞由 CD45 + 低原始细胞群组成。这些细胞常见淋巴细胞 （CD19/CD20/CD22/CD24/cCD79a/CD3/CD5/CD8/CD10） 和髓系抗原 （CD34/CD38/CD13/CD14/CD42b/CD61/CD64/CD65/CD117/cMPO） 阴性，但 CD4 （弱）/CD56/CD123 （强）/HLA-DR （强）/CD33 呈阳性 （图 E 和 F）。在患者背部发现皮肤病变，骨髓穿刺证实 82% 的同一人群具有指示 pDC 谱系的额外表型标志物 （CD303+weak/CD304+/cTCL1+/BadLamp+），支持母细胞性浆细胞样树突状细胞肿瘤 （BPDCN） 的诊断。神经系统检查正常，由于出血性脑脊液样本，脑脊髓受累尚无定论。 此外，对骨髓穿刺物进行的突变谱与 BPDCN 一致，揭示了 TET2 、 ASXL1 和 NF1 突变，以及 IKZF1 和 ETV6 基因座的亚克隆 NRAS 突变和缺失。

BPDCN 是一种罕见的血液系统恶性肿瘤，具有不同的形态学表现。虽然典型的母细胞形态，通常表现出“珍珠项链”细胞质外观和“手镜状”突起，是最常见的表现，但该病例表现出以假淋巴细胞为主的不寻常形态。尽管在 BPDCN 中通常观察到假淋巴细胞亚群，但这种情况非常显着，因为几乎所有细胞都表现出这种独特的形态。这种非典型表现可能具有欺骗性，最初类似于淋巴恶性肿瘤。在这里，免疫表型谱对于建立准确诊断至关重要。