A case of blastic plasmacytoid dendritic cell neoplasm (BPDCN) without cutaneous lesion 

Author: Binglong Wang ¹

Editor: Weifeng Gao²

Chief Editor: Li Yang³

Reviewer: Baohong Yue⁴

¹Department of Clinical Laboratory, The First Affiliated Hospital of Fujian Medical University, Fujian Province, China

²Department of Hematology, Beijing Luhe Hospital, Capital Medical University, Beijing, China

³Department of Clinical Laboratory, Shantou Central Hospital, Guangdong Province, China

⁴Department of Clinical Laboratory, The First Affiliated Hospital of Zhengzhou University, Henan Province, China

Figure 1.Peripheral blood (PB) smear showing tumor cells resembled lymphoblasts, with moderately dispersed chromatin, one to two inconspicuous nucleoli, and scant cytoplasm (Wright stain, original magnification ×1000)

Figure 2. Peripheral blood (PB) smear showing neoplastic cell with pseudopod-like cytoplasmic and irregular nuclei (Wright stain, original magnification ×1000)

Figure 3. Bone marrow (BM) aspirate smear showing neoplastic cells with small to intermediate size, scant cytoplasm, agranular, condensed chromatin and inconspicuous nucleoli (Wright stain, original magnification ×1000)

Figure 4. Bone marrow (BM) aspirate smear showing neoplastic cells with pseudopod-like cytoplasmic and cytoplasmic microvacuoles (Wright stain, original magnification ×1000)

Figure 5. Myeloperoxidase was negative in neoplastic cells (BM, original magnification ×1000)

Figure 6. Periodic Acid-Schiff was positive in neoplastic cells (BM, original magnification ×1000)

Figure 7. Flow cytometry immunophenotype of bone marrow revealed blast cells (red) were positive for HLA-DR, CD33, CD43, CD123, CD56, CD117 (partial), CD36 (partial), CD4 (partial).

Figure 8. Biopsy of cervical lymph node reportedly revealed blastic NK-cell lymphoma.

Figure 9. The bone marrow biopsy findings were consistent with BPDCN. 

A 47-year-old man was referred and admitted to local clinics with pale, cough, expectoration, and neck lymphadenopathy which gradually spread to axilla and groin. On examination, there was no skin lesion and palpable hepatosplenomegaly. He lost 4kg in the last six months. Cough and expectoration were alleviated after anti-inflammatory treatment(details were unknown). However, the lymph nodes were still enlarged. So, he was referred and admitted to our hospital. A full blood count showed a leucocyte count of 3.0×10⁹/L, hemoglobin of 102g/L and platelet count of 51×10⁹/L. Serum levels of lactate dehydrogenase elevated to 641 U/L(normal range, 313–618 U/L). Computed tomography scan of the chest showed many enlarged nodes in the mediastinum and axilla. Lymphoblast-appearing cells (11%) were noted in peripheral blood smear (Fig. 1-2). Bone marrow examination showed 67.5% of blasts (Fig. 3-4). These cells were small to intermediate size, scant cytoplasm, agranular, condensed chromatin and inconspicuous nucleoli. Myeloperoxidase was negative (Fig. 5). Periodic acid-Schiff was positive in 94% abnormal cells (Fig. 6).

Immunophenotyping of bone marrow revealed the CD45^low population (66.0%) was positive for HLA-DR, CD33, CD43, CD123, CD56, CD117 (partial), CD36 (partial), CD4 (partial), and negative for CD13, CD14, CD64, CD19, cMPO, cCD3, CD303, CD304 (Fig.7) . Chromosome analysis was normal. The neck nodes biopsy and immunohistochemistry were in keeping with blastic NK-cell lymphoma (Fig.8), while the bone marrow biopsy findings were consistent with blastic plasmacytoid dendritic cell neoplasm (BPDCN) (Fig.9). Finally, a diagnosis of  BPDCN without cutaneous lesions was made.

BPDCN is a rare, aggressive hematologic malignancy derived from the precursors of plasmacytoid dendritic cells. The disease could occur at any age, but most patients are elderly, with a median/mean age at diagnosis of 60-67 years. The male-to-female ratio is 3.3:1^[1]. BPDCN frequently manifests as cutaneous lesions, followed by dissemination to peripheral blood, bone marrow, and lymph nodes^[2]. It was first reported and recognized by Adachi^[3] in 1994. Many names have been used due to uncertain tissue origin initially, such as agranular CD4(+) natural kill-cell leukemia,CD4(+)/CD56(+) haematodermic neoplasm^[4-5]. With the gradual understanding of this disease, Lucio et al. ^[6] proposed that this type of tumor was related to plasmacytoid dendritic cells in 1999, which was subsequently confirmed by multiple studies. The 2001 WHO Classification named it blastic NK-cell lymphoma based on its cytological and immunophenotypic characteristics ^[7]. In the 2008 WHO Classification, BPDCN was considered to originate from plasmacytoid dendritic cells precursors, which was grouped into “acute myeloid leukemia and related precursor neoplasms”^[8]. With the rapid development of molecular biology, the gene expression profile of BPDCN was confirmed to be distinct from both AML and ALL^[9], which validated its classification as a separate entity among the acute leukemias in the 2016 WHO Classification, rather than as a subtype of AML.

The BPDCN is composed of monomorphic, medium-sized tumor cells, with obvious blastic features resembling either lymphoblasts or myeloblasts. Nuclei display round or irregular, fine to slightly condensed chromatin and one to several small nucleoli. The cytoplasm is usually scant and appears greyish-blue and agranular by Giemsa staining. Some cells present pseudopod-like cytoplasm. The typical neoplastic cell has cirumferential cytoplasmic microvacuoles, which is presentedas pearl necklace. The neoplastic cells in BPDCN are negative for alpha-naphthyl butyrate esterase, naphthol AS-D chloroacetate esterase (CAE), and MPO, while PAS reactivity is strong ^[1].

The typical immunophenotype of tumor cells detected by flow cytometry is positive for CD4, CD43, HLA-DR and CD56, as well as  plasmacytoid dendritic cell related antigens, i.e. CD123(bright), BDCA-2/CD303 and TCL1, but negative for all myeloid and lymphoid lineage antigens, i.e. CD3, CD20, CD79a, myeloperoxidase (MPO), CD11c, CD163 and lysozyme.Some cases variably express the CD2, CD5, CD36, CD38  and CD79a antigens, but not CD13 and CD16 generally ^[10-11]. However, CD4 or CD56 is negative in about 8% of cases which does not exclude the diagnosis if other PDC―associated antigens (in particular CD123, TCL1A, or CD303) are expressed^[1]. The progenitor antigens, CD34 and CD117, are always negative. By immunohistochemistry, BPDCN express the same markers found by flow cytometric, with TCL1 expression. However, TCL1 is not specific for BPDCN, which could be positive in mature B-cell lymphomas and T-cell prolymphocytic leukemia^[12]. Recently, the TCF4(E2-2) transcription factor, which is essential to drive PDCs development, was found to represent a faithful diagnostic marker for BPDCN^[1]. Garnache-Ottou et al. ^[13] had proposed a scoring system (Table 1) for BPDCN based on surface antigen expression. Among the antigens generally overexpressed by BPDCN blasts, CD123 could serve as a therapeutic target of engineered monoclonal antibodies^[14].

Table 1. Scoring system for pDC leukemia/BPDCN diagnosis^[13]

Two thirds of patients with BPDCN have an abnormal karyotype. Specific chromosomal aberrations are lacking, but complex karyotypes are common. Six major recurrent chromosomal abnormalities have been recognized, involving del(5q21) or (5q34) (seen in 72% of cases), del(12p13) (in 64%), del(13q13-21) (in 64%), del (6q23-qter) (in 50%), 15q (in 43%), and loss of chromosome 9 (in 28%). Genomic abnormalities mainly involve tumour suppressor genes or genes related to the G1/S transition; the most recurrent being deletions of CDKN2A. Array-based comparative genomic hybridization shows recurrent deletions of regions on chromosomes 4 (4q34), 9 (9p11–p13 and 9q12–q34), and 13 (13q12-q31), with diminished expression of tumour suppressor genes (RB1, LATS2), whereas elevated expression of the products of the oncogenes HES6, RUNX2, and FLT3 is not associated with genomic amplification^[1].

   The main differential diagnosis is usually made with AML. The blasts of AML with monocytic differentiation can express CD4, CD56, and CD123 and BPDCN cells may resemble myeloblasts or monoblasts. Thus, demonstration of negative for MPO, lysozyme, and NSE is important, as positivity for any of these three markers would favor AML rather than BPDCN. One recent study suggested that a panel of immunohistochemical markers including MPO, CD56, CD123, TCL1, TdT, and myxovirus A was most helpful in distinguishing between AML and BPDCN ^[15]. Furthermore, BPDCN must also be distinguished from mature plasmacytoid dendritic cell proliferation (MPDCP) associated with other myeloid neoplasms (most commonly chronic myelomonocytic leukaemia, MDS, or AML). Unlike the tumor cells of BPDCN, the cells in mature plasmacytoid dendritic cell nodules have abundant, eccentric cytoplasm reminiscent of plasma cells and mature chromatin, which morphologically similar to normal PDCs. The PDCs in these nodules generally have the same phenotype as their normal counterparts, although in occasional cases aberrant single or multiple antigen expression (e.g. of CD2, CD5, CD7, CD10, CD13, CD14, CD15, and/or CD33) has been reported. Most importantly, CD56 is negative in most cases, or shows only focal and weak reactivity. The PDCs in MPDCP have a low Ki-67 proliferation index (<10%)and lack TdT and CD34 ^[1].

Here, we reported a 47-year-old man who was diagnosed with BPDCN without skin lesions, presenting with pancytopenia and lymphadenectasis. Such patient could be liable to be misdiagnosed as ALL based on morphological and histochemical results alone, so the comprehensive diagnosis of MICM and pathological biopsy combined with clinical manifestations is very important.

References

[1]Swerdlow SH, Campo E, Harris NL, et al. (Eds): WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues (Revised 4th edition). IARC: Lyon 2017.

[2] Pilichowska ME, Fleming MD, Pinkus JL, et al. CD4+/CD56+ hematodermic neoplasm (‘blastic natural killer cell lymphoma’): neoplastic cells express the immature dendritic cell marker BDCA-2 and produce interferon. Am J Clin Pathol, 2007,128:445-453.

[3] Adachi, M., Maeda, K., Takekawa, M., et al. High expression of CD56 (N-CAM) in a patient with cutaneous CD4-positive lymphoma. Am J Hematol, 1994, 47(4), 278-282.

[4] Marafioti T, Paterson JC, Ballabio E, et al. Novel markers of normal and neoplastic human plasmacytoid dendritic cells. Blood, 2008, 111:3778–3792.

[5] Urosevic M, Conrad C, Kamarashev J, et al. CD4+CD56+ hematodermic neoplasms bear a plasmacytoid dendritic cell phenotype. Hum Pathol, 2005, 36:1020-1024.

 [6] Lucio P, Parreira A, Orfao A. CD123hi dendritic cell lymphoma: an unusual case of non-Hodgkin lymphoma. Ann Intern Med, 1999, 131:549-550.

[7] Jaffe ES, Harris NL, Stein H, et al. World Health Organization classification of tumours of haematopoietic and lymphoid Tissues. Lyon: IARC Press; 2001.

[8] Vardiman JW, Thiele J, Arber DA,et al. The 2008 revision of the World Health Organization(WHO）classification of myeloid neoplasms and acute leukemia:rationale and important changes. Blood, 2009, 114(5):937-951.

[9] Sapienza, MR., Fuligni, F, Agostinelli, C, et al. Molecular profiling of blastic plasmacytoid dendritic cell neoplasm reveals a unique pattern and suggests selective sensitivity to NF-kB pathway inhibition. Leukemia, 2014, 28(8):1606-1616.

[10] Chaperot L, Bendriss N, Manches O, et al. Identification of a leukemic counterpart of the plasmacytoid

dendritic cells. Blood, 2001, 97:3210-3217.

[11] Petrella T, Bagot M, Willemze R, et al. Blastic NK-cell lymphomas (agranular CD4+CD56+ hematodermic neoplasms): a review. Am J Clin Pathol, 2005, 123:662–675.

[12] Herling, M, Teitell MA, Shen RR, et al. TCL1 expression in plasmacytoid dendritic cells (DC2s) and the related CD4+CD56+ blastic tumors of skin. Blood, 2003, 101:5007–5009.

[13] Garnache-Ottou F, Feuillard J, Ferrand C, et al. Extended diagnostic criteria for plasmacytoid dendritic cell leukaemia. Br J Haematol, 2009, 145(5):624-636.

[14] Ugo Testa, Elvira Pelosi, Arthur Frankel.CD 123 is a membrane biomarker and a therapeutic target in hematologic malignancies. Biomark Res, 2014, 2:4.

[15] Sangle NA, Schmidt Rl, Patel JL, et al. Optimized immunohistochemical panel to differentiate myeloid sarcoma from blastic plasmacytoid dendritic cell neoplasm. Mod Pathol, 2014, 27(8): 1137-1143.

（Executive editor：Hui Zhang，Department of Clinical Laboratory,Henan Honliv Hospital, Henan Province, China）

 一例無皮損的母細胞性漿細胞樣樹突細胞腫瘤

作者：王炳龍  福建醫(yī)科大學(xué)附屬第一醫(yī)院檢驗科

編輯:  郜偉峰 首都醫(yī)科大學(xué)附屬北京潞河醫(yī)院血液科

主編:  楊 禮 汕頭市中心醫(yī)院檢驗科

審稿專家：岳保紅 鄭州大學(xué)第一附屬醫(yī)院檢驗科

病史摘要：男性，47 歲，出現(xiàn)頸部淋巴結(jié)腫大，質(zhì)地韌，活動度可，無壓痛，伴咳嗽、咳痰，呈淡黃色，后漸波及腋下、腹股溝淋巴結(jié)，無痰中帶血，伴面色蒼白，無低熱、盜汗，無頭暈、頭痛，無惡心、嘔吐，無鼻出血、牙齦出血，無血尿，無尿頻、尿急、尿痛，無皮疹、關(guān)節(jié)痛，無口腔破潰，就診于當(dāng)?shù)蒯t(yī)院，予抗炎治療(具體不詳)后咳嗽、咳痰明顯好轉(zhuǎn)，淋巴結(jié)腫大無明顯消退，半年內(nèi)體重減輕約4 kg。

影像學(xué)檢查：CT示肺部平掃未見明顯異常；縱隔及雙側(cè)腋窩多發(fā)淋巴結(jié)腫大，請結(jié)合臨床。

相關(guān)實驗室檢查：

血常規(guī)：

生化：

外周血涂片：可見原始細胞占11%

骨髓涂片：骨髓增生極度活躍，原始細胞約占67.5%，細胞體積大小不均，胞漿量少，核染色質(zhì)較粗，可見核仁

細胞化學(xué)染色：POX陰性， PAS 94%陽性。

流式細胞學(xué)檢查：CD45弱陽性細胞占有核細胞總數(shù)69.1%，HLA-DR+，CD33+ ，CD43+， CD123+，CD56+，部分表達CD117，CD36，CD4，CD13-，CD14-，CD64-，CD19-， cMPO-，cCD3-，CD303-，CD304-。

染色體核型：

頸部淋巴結(jié)活檢：結(jié)合免疫組化符合母細胞性NK細胞淋巴瘤。

骨髓活檢：結(jié)合免疫組化考慮母細胞性漿細胞樣樹突細胞腫瘤。

最后診斷：母細胞性漿細胞樣樹突細胞腫瘤（BPDCN）

病例聚焦：

一、定義和起源

母細胞性漿細胞樣樹突細胞腫瘤 (blastic plasmacytoid dendritic cell neoplasm，BPDCN)是一種罕見的、侵襲性的血液惡性腫瘤，起源于漿細胞樣樹突細胞的前體細胞，該病可于任何年齡段發(fā)病，但好發(fā)于老年60-67歲，男女比例為3.3:1^[1]。常侵犯皮膚，其次是骨髓，外周血和淋巴結(jié) ^[2]。它最早由Adachi^[3]在1994年被報道和認識。最初，由于不能確定其組織來源，已經(jīng)更換過好多名稱，如無顆粒CD4+NK細胞白血病、無顆粒CD4+CD56+血液皮膚腫瘤等^[4-5]。隨著對該疾病的逐漸認識，1999年Lucio等 ^[6]首先提出此類腫瘤與漿細胞樣樹突細胞有關(guān)，隨后被多個研究證實。WHO 2001根據(jù)其細胞學(xué)和免疫表型特征將其命名為母細胞性NK細胞腫瘤^[7]。WHO 2008^[8]將其命名為BPDCN，并將其劃分在急性髓系白血病及相關(guān)前體細胞腫瘤里。后來，隨著分子生物學(xué)地快速發(fā)展，發(fā)現(xiàn)BPDCN的基因表達與AML和ALL均不同^[9]，因此，在最新的WHO 2016修訂版中將其分離出來成為獨立的一種疾病。

二、形態(tài)學(xué)特點

  BPDCN的腫瘤細胞胞體中等大小，胞漿量少或中等，灰藍色，嗜堿性不均勻，可見偽足突出(拖尾細胞)，典型的瘤細胞可見沿胞膜下特征性的呈珍珠項鏈樣排列的空泡，極少許細胞可有少許粗大的紫紅色顆粒，細胞化學(xué)染色α-萘酚-丁酸酯酶、氯乙酸AS-D萘酚酯酶 (CAE)和MPO均為陰性，PAS陽性，呈圓珠樣、顆粒狀或大塊狀陽性^[1]。

三、免疫表型

 流式細胞檢測BPDCN典型的腫瘤細胞表現(xiàn)為系別抗原陰性（如B 細胞(CD20，CD79a), T 細胞 (CD3), 髓系抗原 (MPO)，單核細胞(CD11c， CD163，lysozyme)）表達HLA-DR，CD43，CD4，CD56以及漿細胞樣樹突細胞細胞相關(guān)抗原CD123、BDCA-2/CD303、TCL1。在淋系和髓系相關(guān)抗原中，CD7和CD33表達較常見。有些病例會表達CD2，CD5，CD36，CD38，CD79a，一般不會表達CD13,CD16^[10-11]。8%病例可出現(xiàn)CD56或CD4陰性，但如果CD303、CD123和TCL1陽性并不能排除這一診斷^[1]。病理免疫組織化學(xué)染色表達標(biāo)志與流式檢測的標(biāo)志類似，TCL1陽性。但是TCL1陽性并不特異，因為在成熟B細胞淋巴瘤和T幼稚淋巴細胞白血病中也表達該抗原^[12]，因此需要一系列相關(guān)抗原綜合判斷。Garnache-Ottou 等 ^[13]提出以細胞表面抗原表達為基礎(chǔ)的 BPDCN 評分系統(tǒng) (表 1)。該診斷標(biāo)準為，腫瘤細胞不表達系別抗原，同時表達至少一種漿樣樹突細胞相關(guān)抗原如CD123, TCL1, CD2AP 和BDCA2/CD303。當(dāng)總積分>2時，診斷成立。WHO 2016修訂版 ^[1]中指出TCF4 (E2-2)轉(zhuǎn)錄因子被發(fā)現(xiàn)是BPDCN的一個可靠的診斷標(biāo)志物，它對PDCs的發(fā)育起著至關(guān)重要的作用。在BPDCN原始細胞普遍過表達的抗原中，CD123可以作為單克隆抗體的治療靶點^[14]。

表1. BPDCN診斷積分系統(tǒng)^[13]

備注：BDCA-2：CD303；BDCA-4：CD304

四、染色體和分子遺傳學(xué)特點

2/3的BPDCN患者有核型異常。缺乏特異性染色體異常，但復(fù)雜核型常見。已報道6種主要的重現(xiàn)染色體異常，包括5q21或5q34(見于72%病例)、12p13(見于64%病例)、13q13-21(見于64%病例)、6q23-qter(見于50%病例)、15q(見于43%病例)和9號染色體缺失(見于28%病例)。基因異常主要累及腫瘤抑制基因或與G1/S轉(zhuǎn)化相關(guān)的基因，最常見的是CDKN2A的缺失?；陉嚵械谋容^基因組雜交顯示染色體4 (4q34)、9 (9p11-p13和9q12-q34)和13 (13q12-q31)區(qū)域的重現(xiàn)性缺失導(dǎo)致腫瘤抑基因(RB1, LATS2)表達減少，而癌基因HES6、RUNX2和FLT3產(chǎn)物表達升高不伴有基因組擴增^[1]。

五、鑒別診斷

由于本例BPDCN，缺乏皮膚損害，且細胞形態(tài)與髓系、淋系原始細胞相似，過氧化物酶陰性，PAS陽性，形態(tài)學(xué)上需與ALL相鑒別；免疫表型細胞表達CD33，CD4和CD123，部分表達CD117，需與急性髓系白血病AML-M5相鑒別。如果MPO、溶菌酶或NSE有陽性，那么考慮診斷為AML-M5而非BPDCN。有研究表明，同時檢測MPO、CD56、CD123、TCL1和TdT、黏病毒A能夠很好的鑒別AML-M5和BPDCN^[15]。BPDCN可表達CD56，易與NK細胞白血病相混淆，因此在確診BPDCN之前需要應(yīng)用一系列髓系、單核細胞標(biāo)記和BPDCN相對特異的CD303/CD304和TCL1進行鑒別。

此外，BPDCN必須與髓系腫瘤相關(guān)MPDCP（mature plasmacytoid dendritic cell proliferation，MPDCP）進行鑒別。MPDCP細胞形態(tài)上較成熟，與正常PDCs相似，常常累及皮膚（皮疹、斑點或丘疹，極少有皮膚結(jié)節(jié)）、淋巴結(jié)和或骨髓。MPDCP常常與髓系腫瘤有關(guān)，最常見的是CMML、MDS或AML伴單核細胞分化。MPDCP的PDCs除了表達PDCs相關(guān)抗原(CD123，CD303，CD2AP，TCL1)外，還表達CD2，CD5，CD7，CD10，CD13，CD14，CD15和CD33，但絕大部分不表達CD56,或表達強度極弱。 Ki-67增殖指數(shù)很低，常<10%，不表達TdT和CD34^[1]。

參考文獻：（同英文部分，略）

（責(zé)任編輯：張輝 河南宏力醫(yī)院）

注：投稿方式：來稿請發(fā)至郵箱xyxsytk@outlook.com，同時請備注典型細胞圖庫投稿、或病例圖庫投稿、或細胞趣圖圖庫投稿。來稿請注明作者姓名、單位、標(biāo)本來源、染色方法、放大倍數(shù)，以便我們標(biāo)明出處！請注意全部圖片和病史資料一定要原創(chuàng)，保護原創(chuàng)作者的知識產(chǎn)權(quán)！

建立中國人自己的血液學(xué)中英文雙語圖庫，任重道遠，讓中國的細胞形態(tài)學(xué)走向世界，讓血液學(xué)圖庫增添更多的中國力量，需要大家的積極參與，歡迎各位同道踴躍來稿！我們一起努力加油！