CD31/PECAM-1-driven chemokine-independent transmigration of human T lymphocytes

We assessed the relative contribution of CD31/PECAM-1 (platelet-endothelial cell adhesion molecule-1) to T lymphocyte transmigration by the use of transfected murine fibroblasts stably expressing either the human CD31/PECAM-1 or the intercellular adhesion molecule-1 (CD54/ICAM-1). Unlike CD54/ICAM-1, CD31/PECAM-1 supported migration of activated T cells in the absence of chemokines: most of the migrating lymphocytes were CD31⁺ and displayed a phenotype corresponding to the naive subpopulation (LFA-1^dull and CD45RA⁺). Migration of activated T lymphocytes through CD54/ICAM-1⁺ transfected monolayers could be induced by creating a chemotactic gradient with the chemokine monocyte chemotactic protein-1, and the migrating cells mainly displayed a memory phenotype (LFA-1^brightCD45RO⁺) under these conditions. Furthermore, we found that in transfected cells CD54/ICAM-1 is uniformly distributed along the apical surface of the cells, while CD31/PECAM-1 is concentrated at the intercellular junctions, suggesting the existence of a haptotactic gradient (i.e. a gradient of substrate- or cell-bound molecules) responsible for T cell migration. This was also confirmed by the finding that monolayers of murine fibroblasts transfected with a CD31/PECAM-1 mutant lacking the cytoplasmic domain (CD31/PECAM-1-Δcyto), which has a reduced tendency to localize at cell-cell contact areas, supported efficient adhesion but were unable to induce migration of activated T cells unless a chemotactic gradient was created. We propose that in lymphocytes, homophilic CD31/PECAM-1 adhesion may be primarily involved in transmigration of naive T cells and that its role is complementary to that of CD54/ICAM-1.     

Comparative study of adhesion molecule expression in cultured human macro- and microvascular endothelial cells

Culture systems as models for disease are only valid as long as they are comparable to in vivo conditions. The phenotype of cultured endothelial cells (ECs) has only been sporadically compared to the corresponding phenotype in vivo. Thus, we compared by immunolocalization the endothelial expression of ICAM-1, VCAM, and E-selectin in vivo in stimulated/unstimulated human umbilical vein endothelial cells (HUVEC) as a model for macrovascular ECs and stimulated/unstimulated HPMEC (human pulmonary microvessel endothelial cells) as a model for pulmonary microvascular ECs with that in human lungs in vivo (normal and ARDS). Proinflammatory stimuli in vitro were used to stimulate conditions relevant for ARDS. ICAM-1 expression in stimulated HUVEC/HPMEC correlated well with in vivo expression (macro- and microvessels). For E-selectin, the staining pattern in macro/microvessels correlated moderately with unstimulated and well with stimulated HUVEC/HPMEC. For VCAM a good correlation was found for stimulated/unstimulated HUVEC and unstimulated HPMEC. The expression patterns in stimulated HUVEC corresponded well for all three molecules with those in vivo. Thus, the expression patterns in vitro are only partially transferable to in vivo conditions. The study suggests that E-selectin- and VCAM-coated beads could potentially serve in the isolation process of arteriolar and venular ECs.     

白血病CD34与MDR1表达的调控关系

目的 :探讨白血病CD34分子与MDR1分子表达的调控关系。方法 :采用流式细胞术双标记法检测 30例白血病外周血细胞CD34分子和MDR1分子的表达。结果 :白血病外周血细胞CD34分子表达与MDR1分子表达密切相关 (r =0 92 ,P <0 0 1) ;经曲线回归分析表明 ,CD34分子表达调控着MDR1分子的表达 ,且呈一元二次曲线关系 (R2 =0 88) ;回归方程式为 :MDR1=1 79 0 94CD34 0 0 1CD342 。结论 :在白血病外周血细胞中 ,CD34分子的表达调控MDR1分子的表达。     

Expression of CD34 in endothelial cells,hematopoietic progenitors and nervous cells in fetal and adult mouse tissues

The human cell surface molecule CD34 is selectively expressed on uncommitted and committed hematopoietic progenitor cells and on vascular endothelial cells. It has been suggested that CD34 regulates early events in blood cell migration and differentiation, possibly as a cell adhesion molecule. To characterize the patterns of expression of CD34 in the mouse embryo and in the adult, as well as to dissect the function of different portions of the extracellular domain of this molecule, we have generated the first monoclonal antibodies (mAb) specific for mouse CD34. The epitope(s) recognized by these mAb are not carbohydrate moieties, and are comprised either within the immunoglobulin-like domain or within a portion of the mucin domain, containing approximately half of the predicted O- and N-linked carbohydrate attachment sites. The specificity of the antibodies was established by ELISA and Western blotting. Western analysis revealed that these mAb recognize a protein of approximately 110 kDa in PA6 stromal cell lysates, which can be specifically blocked by the recombinant CD34 protein. To establish the reactivity of these mAb on different cell lineages, a panel of cell lines was stained. This analysis showed strong reactivities with 3T3 fibroblasts, stromal cell lines from fetal liver and with the endothelial cell line D10. Bone marrow hematopoietic progenitors were also stained by these mAb. Immunostaining of frozen sections from embryonic and adult tissues revealed a strong reactivity against vascular endothelial cells at different stages of development, including sinusoidal cells in the fetal liver, yolk sac, and in the fetal bone marrow, endothelial cells from adult lung and kidney, and neural cells, including those of the neural tube of midgestation embryos and neuronal bodies in adult brain.     

SARS肺组织中CD34、VEGF、ICAM-1的表达及其意义

目的 通过对严重急性呼吸综合征(SARS)肺组织中CD34、血管内皮生长因子(VEGF)和细胞问黏附分子(ICAM-1)表达水平的检测对其发病机制进行探讨.方法 将7例死亡SARS病例及同期6例具有急性肺损伤性临床表现的非SARS死亡病例肺标本对照进行HE染色及CD34、VEGF、ICAM-1免疫组化检查,并对免疫组化染色结果进行图像分析.结果 CD34染色结果显示SARS组肺毛细血管内皮细胞着色浓重胞膜完整、排列紊乱但细胞连续性好,平均光密度值(MOD)为0.284 3±0.103 3;非SARS组肺组织CD34染色浅淡、不连续,MOD值为0.129 7±0.007 3,两组结果差异有显著性(P=0.007 4);不合并细菌或真菌感染SARS标本的MOD值为0.342 8±0.031 6,与非SARS组结果差异有显著性(P＜0.000 1).SARS组VEGF阳性染色MOD为0.125 3±0.042,与非SARS组0.114 3±0.025 2相比,结果差异无统计学意义(P=0.5888).两组ICAM-1阳性染色MOD值差异无统计学意义;但不合并感染的SARS标本ICAM-1 MOD值为0.255 7±0.045 2,与非SARS组0.182±0.017相比,结果差异有统计学意义(P=0.006).结论 SARS肺脏中内皮细胞的损伤程度较之其他原因引起的肺组织损伤轻,ICAM.1和VEGF表达也存在不同,这些差异可能反映了SARS肺损伤的特殊性,对解释SARS的临床和病理生理过程具有一定意义.     

白藜芦醇提高CD34+CD38-KG1a白血病细胞对人外周血单个核细胞的杀伤敏感性

目的:研究白藜芦醇(Resveratrol)作用前后CD34+CD38-KG1a白血病细胞对IL-15介导的人外周血单个核细胞(PBMC)杀伤敏感性的变化及机制的初步探讨.方法:应用CCK-8法检测白藜芦醇对白血病细胞的IC50值,以此量的白藜芦醇作用于白血病细胞.,并用LDH释放法检测白藜芦醇作用前后,效靶比分别为5∶1、10∶1、20∶1的IL-15介导的PBMC对CD34+CD38-KG1a细胞杀伤能力.流式细胞仪(FACS)检测IL-15介导前后PBMC表面NKG2D的表达.流式细胞仪(FACS)检测作用前后CD34+CD38-KG1a细胞表面NKG2D配体(MICA、MICB、ULBP1、ULBP2、ULBP3)表达.结果:白藜芦醇作用前后在不同效靶比时对IL-15介导的PBMC杀伤敏感性差异有统计学意义(P＜0.05).IL-15介导PBMC前后表面NKG2D的表达有显著变化,差异有统计学意义.白藜芦醇作用前后CD34+CD38-KG1a细胞表面NKG2D各配体中MICA、MICB无显著变化(P＞0.05),ULBP1、ULBP2、ULBP3有显著变化,差异有统计学意义(P＜0.05).结论:白藜芦醇可以提高CD34+CD38-KG1a细胞对IL-15介导PBMC的杀伤敏感性,其机制可能与白藜芦醇提高CD34+CD38-KG1a细胞表面NKG2D配体的表达有关.     

小鼠肌源性干细胞高表达CD34、 Sca-1、Bcl-2和desmin

目的: 探讨小鼠肌源性干细胞(MDSCs)的生物学特性和表型。方法: 取小鼠骨骼肌,用酶分步消化,应用差速贴壁法进行纯化获取MDSCs,观察细胞的形态,对MDSCs分别进行增殖能力、克隆形成率和融合情况等鉴定;通过流式细胞术、免疫荧光法及免疫印迹法(Western blotting)等检测初步确定细胞表型。结果: 经差速贴壁法获取的MDSCs为圆形或短梭形细胞,聚集成簇,呈对数生长;细胞倍增时间(9.69±2.08)h,克隆形成率(13.35±2.54)%;细胞在高汇合度(>50％)或低血清(2％FBS)培养时,极易融合成肌管或肌细胞链;流式细胞术和免疫荧光技术鉴定:CD34、Sca-1、Bcl-2和desmin在原代MDSCs中的表达均>90%;Western blotting检测显示随着细胞的纯化, desmin表达越来越强,α-SMA表达越来越弱。结论: MDSCs通过差速贴壁法获取时纯度较高,它具有高水平表达CD34、Sca-1、Bcl一2和desmin的生物学特性,这4种蛋白可作为鉴定MDSCs的标志物。MDSCs增殖旺盛,可在体外大量扩增,是组织工程研究的一种新型种子细胞。     

Expression of human NKRP1A by CD34+ immature thymocytes: NKRP1A-mediated regulation of proliferation and cytolytic activity

In this study, we show that NKRP1A is expressed and functions on a subset of immature human thymocytes. We took advantage of the monoclonal antibody (mAb) 191B8 that was obtained by immunizing mice with cultured human thymocytes characterized by an immature surface phenotype [CD2^? CD3^? CD4^? CD8^? stem cell factor receptor (SCFR)⁺] and expressing cytoplasmic CD3? chain. The 191B8 antibody homogeneously reacted with the immunizing population but not with most unfractionated thymocytes. It stained a minor population of resting immature thymocytes co-expressing CD34, SCFR, or both. Following culture of the CD34⁺ or CD34^? fractions of CD2^? CD3^? CD4^? CD8^? purified immature thymocytes with recombinant interleukin-2 (rIL-2), the 191B8-defined antigen was expressed on virtually all cells even when 191B8⁺ cells were removed from the starting population. On the other hand, no 191B8⁺ cells were detected in fresh or cultured thymocytes expressing a more mature phenotype. Biochemical analysis of 191B8 mAb-reactive molecules revealed, under non-reducing conditions, two bands displaying apparent molecular masses of 80 and 44 kDa and a single band of 44 kDa under reducing conditions. Digestion with proteases indicated that the 80-kDa form represented a homodimeric form of two 44-kDa molecules, while deglycosylation with N-glycanase suggested the existence of four N-glycosylation sites. Transfection of COS7 or NIH3T3 cells with hNKRP1A cDNA showed that the 191B8 mAb recognized NKRP1A as shown by both immunofluorescence analysis and immu-noprecipitation experiments. Functional studies showed that the 191B8/NKRP1A molecule mediated strong inhibition of the cytolytic activity of culturd CD2^? CD3^? immature thymocytes against a panel of tumor target cells. More importantly, 191B8 mAb induced proliferation of CD2^? CD3^? fresh thymocytes which was not increased by rIL-2. Thus, we propose that NKRP1A molecules, which are expressed in highly immature thymocytes, may play a regulatory role in their growth and function.     

CD34抗原在脂肪组织肿瘤中的表达及其病理意义

目的：研究CD34在脂肪组织中的表达并探讨其临床病理意义。方法：对11例脂肪瘤、4例血管脂肪瘤、4例血管平滑肌脂肪瘤、1例梭形细胞脂肪瘤和8例脂肪肉瘤进行CD34免疫组化法检测,观察CD34的表达分布怦况并结合各肿瘤的组织学特征进行分析。结果：除血管内皮细胞均为强阳性外,CD34阳性细胞包括梭形间质细胞和少数多泡状脂母细胞,成熟脂肪细胞为阴性。该抗原在11例脂肪瘤及2例血管脂肪瘤中均为阳性表达,在另2例血管脂肪瘤中为局灶阳性,在4例血管平滑肌脂肪瘤中为阴性表达,在梭形细胞脂肪瘤、脂肪瘤样型脂肪肉瘤及2例黏液性脂肪肉瘤中为强阳性表达,在5例去分化脂肪肉瘤中的表达情况多样,1例为完全阴性,1例为完全阳性,另3例存在阴性、阳性及强旨性区域混杂的情况。结论：脂肪组织肿瘤中存在一类CD34阳性的梭形间质细胞,CD34的表达情况可能与去分化脂肪肉瘤的去分化程度相关,该抗原可以作为梭形细胞脂肪瘤与其他梭形细胞肿瘤的鉴别诊断指标之一。     

CD55、CD59、CD34对AA-PNH早期诊断研究应用

目的：探讨CD55、CD59、CD34抗原在再障．阵发性血红蛋白尿综合征(AA-PNH)的早期诊断中的价值，寻找AA-PNH早期诊断敏感指标，进而达到早期发现、早期诊断、早期治疗的目的。方法：应用流式细胞仪测定AA-PNH综合征患者的CD55、CD59、CD34抗原变化关系，并与PNH、AA等疾病组以及正常对照组CD55、CD59、CD34抗原相互变化关系，经过统计学处理，找出相关性。结果：结果表明AA—PNH、PNH CD55、CD59、CD34抗原较AA及其他疾病组及正常对照组明显减低，并与溶血试验中溶血程度呈正相关，且早于其他溶血指标。结论：CD55、CD59、CD34抗原表达率可作为PNH、AA-PNH综合征早期诊断最敏感指标，并与预后转归密切相关。     

Enhanced CD34 expression of sinusaid-like vascular endothelial cells in hepatocellular carcinoma

The immunohistochemlcal expression of CD34 (human hematopoletic stem cell and endothelial cell marker) and laminin were studied In chronic liver diseases and hepate cellular carcinoma (HCC) to elucidate whether their expression reflected phenotypic differences between non-cancerous slnusoids and sinusoid-like tumor vessels. In normal liver, hepatic sinusoids were always negative for CD34 and lami-nin. In chronic hepatitis and cirrhosis, the two antigens were sparsely expressed in capillarized sinusoids at periportal and petinodular area. In advanced HCC, CD34 was strongly and diffusely expressed by the endothelial lining of sinusoid-like tumor vessels. However, early-stage HCC showed a wide spectrum of CD34 expression from negative to focal and diffuse, strongly positive staining in sinusoid-like vessels. Laminin was strongly expressed in advanced HCC but not in early-stage HCC. The results Indicate that the enhanced expression of CD34 by sinusoidal endothelial cells may reflect the phenotypic change of endothellal cells in chronic liver diseases and HCC, and that the expression may correlate with the processes of angiogenesis induced by hepatocarcinogenesis.     

NRP-1、P53和CD34在大肠癌组织中的表达及临床意义

目的探讨大肠癌组织中P53、NRP1和CD34表达的意义及相关性。方法选取62例大肠癌和30例正常大肠粘膜组织标本,采用免疫组化方法检测正常大肠粘膜及大肠癌组织中P53的表达,免疫组化和Western blot方法检测正常大肠粘膜及大肠癌组织中NRP1和CD34表达情况,测定微血管密度,并进行相关性分析。结果免疫组化结果发现,NRP-1和p53在大肠癌组织的阳性表达率显著高于正常大肠粘膜组(P<0.05),CD34阳性产物MVD值大肠癌组显著高于正常大肠粘膜组(P<0.05)。Western blot结果显示,与正常粘膜组织相比,大肠癌组织中NRP1、CD34的表达水平显著升高(P<0.05)。结论 NRP-1、p53、CD34在大肠癌组织中过表达并呈正相关。     

IKCa1通道阻滞剂TRAM-34对HUVEC增殖作用的影响

目的 体外应用IKCa1通道阻滞剂TRAM-34干预人脐静脉内皮细胞(HUVEC),探讨其抑制HUVEC增殖作用的影响.方法 采用免疫荧光和RT-PCR法观察HUVEC细胞IKCa1的表达,常规MTT法分析不同浓度TRAM-34作用24、48、72 h后HUVEC细胞增殖的变化.结果 免疫荧光和RT-PCR法均证实HU...     

哮喘豚鼠模型肺和骨髓中CCR3及CD34的表达及意义

目的:观察哮喘豚鼠肺和骨髓组织CCR3及EOS不同时相表达的变化, 探讨哮喘发病的可能机制.方法:用卵白蛋白(OVA)和生理盐水致敏法制备豚鼠哮喘和对照模型, 分为正常对照组(N)及哮喘组(A、B、C、D、E), 每组8只, 于激发后30 min, 6 h, 12 h, 24 h, 48 h处死, 瑞氏染色计数骨髓涂片和外周血涂片中EOS比例, 免疫组织化学技术检测骨髓中CCR3及CD34蛋白的表达;制备豚鼠肺组织病理标本, 苏木精-伊红染色, 免疫组化检测肺组织中CCR3和CD34的表达.结果:(1)哮喘组骨髓和外周CCR3与CD34及EOS表达明显增加;(2)OVA激发后, 骨髓和外周CCR3、CD34及EOS表达:30 min变化不明显(肺内CD34表达增加), 6 h(肺内CD34表达下降)、12 h达到峰值, 24 h开始下降, 48 h恢复正常水平;(3)骨髓的变化早于外周, CCR3的表达高峰早于CD34表达与EOS的增多高峰, 且CCR3、CD34和EOS互呈线性相关(肺组织内除外).结论:哮喘豚鼠肺组织和骨髓之间存在骨髓CD34 祖细胞、EOS细胞到循环再到肺组织的通路, 骨髓和肺组织CCR3表达增强, 为CD34 细胞、EOS从骨髓快速募集到肺组织提供了可能.     

CD34在体外培养大鼠骨骼肌卫星细胞发育的免疫组织化学研究

目的 观察CD34在发育中的体外培养大鼠骨骼肌卫星细胞中的分布，探讨CD34在发育中的大鼠骨骼肌卫星细胞中的作用。方法 原代培养骨骼肌卫星细胞，第1次传代后，取贴壁2、4、8、16、24、48和72h的细胞行CD34多克隆抗体的免疫组织化学染色。结果 CD34免疫阳性反应存在于发育中的骨骼肌卫星细胞中，但在形成肌管后，细胞核免疫反应转为阴性，同时成纤维细胞呈弱阳性反应。结论 CD34在发育中的骨骼肌卫星细胞中有一定量的分布，它可能在骨骼肌的生理发育中起某种调节作用。     

Expression of CD34 antigen in testicular mixed germ cell tumor

The expression of CD34 was investigated in 14 cases of testicular mixed germ cell tumor to elucidate the relationship between its expression and histological patterns. Seven of 12 yolk sac tumor components were focally immunoreactive for anti-CD34 antibody. Of these, five showed focal but intense CD34 staining, while the remaining two tumors showed weak staining in small clusters or isolated tumor cells. Positive immunostaining for CD34 was seen predominantly in solid and reticular patterns of the yolk sac tumor components. Seminoma, embryonal carcinoma, and choriocarcinoma components were invariably negative for CD34. If present, immunoreactivity for CD34 in yolk sac tumors is focal and variable, but useful for the distinction from other germ cell tumors.     

抗CD40抗体联合诱导人脐血CD34+造血干细胞向DC2分化的作用

目的 探讨从脐血CD34^＋造血细胞诱导DC2的方法及CD40分子在DC2分化诱导中的作用。方法 运用磁珠从脐血中分离出CD34^＋造血干细胞,以rhIL-3（10ng／mL）、rhFlt-3L（100ng／mL）和rhGM-CSF（100ng／mL）诱导其向DC2分化,采用流式细胞仪分析DC2表型,并观察抗人CD40单克隆抗体诱导DC2分化成熟的作用。结果 人脐血CD34^＋造血细胞在rhIL-3、rhFlt-3L和rhGM-CSF联合诱导培养12d,获得具有DC2样（淋巴样DC）形态的细胞,然后分别加入rhIL-3＋抗人CD40 mAb（Ⅰ组）或rhIL-3＋TNF-α（Ⅱ组）诱导DC2的分化成熟,流式细胞仪分析细胞表型,发现Ⅰ组和Ⅱ组Lineage^-（CD3、CD14、CD16、CD19、CD56）CD123^＋细胞的HLA-DR、CD83、CD86、CD80表达率分别为88．78％、37．38％、32．83％和99．08％;78．87％、32．29％、29．57％和98．86％。结论 体外联合多种细胞因子从CD34^＋造血细胞成功地诱导出富集DC2表型的细胞,抗人CD40 mAb可以促进DC2的分化成熟。     

Immunoreactivity of sinusoids in hepatoblastoma: an immunohistochemical study using lectin UEA-1 and antibodies against endothelium-associated antigens, including CD34

Sinusoids are found not only in the normal liver but also in certain liver tumours, including hepatoblastoma, the most common malignant liver tumour in childhood. In this study, sinusoids in 12 hepatoblastomas, of various subtypes, and in normal liver were investigated with UEA-1 and antibodies against von Willebrand's factor, CD31 and CD34 to detect differences of possible diagnostic significance. In the normal liver, staining of sinusoids was seen with all these markers, but it was focal and confined to a few sinusoids near the portal tracts. In hepatoblastoma, the endothelial markers reacted with the sinusoids to varying extents. UEA-1 and anti-CD34 usually stained the majority of these vessels, anti-CD34 staining greater numbers of sinusoids and with greater intensity. Immunostaining revealed that both number and spatial organization of sinusoids in hepatoblastoma are dependent on the subtype. In addition to staining of endothelium, one of the two small cell hepatoblastomas exhibited strong immunoreactivity of the tumour cells for CD34. These findings show that the marked difference in sinusoidal immunoreactivity for CD34 between normal liver and hepatoblastoma could be useful for discriminating between non-neoplastic liver tissue and highly differentiated fetal hepatoblastoma. Our findings also show that small cell hepatoblastoma, in addition to acute leukaemia, should be considered when immunoreactivity for CD34 is found in small round and blue cell tumours in childhood.     

尖锐湿疣表皮CD1a和CD207的表达

目的:了解尖锐湿疣(CA)表皮中CD1a和CD207的表达情况及其意义.方法:采用寡核苷酸芯片对6例CA表皮和6例正常表皮中的CD1a和CD207的mRNA表达进行检测,应用半定量RT-PCR验证CD1a和CD207的mRNA表达,采用Western blot法检测6例CA表皮和6例正常表皮中的CD1a和CD207的蛋白表达.结果:基因芯片检测到CD1a和CD207的mRNA在CA表皮中表达下调,半定量RT-PCR证实CD1a和CD207的mRNA在CA表皮中表达下调,Western blot法检测到CD1a和CD207蛋白在CA表皮中的显著下调表达.结论:CA表皮中CD1a和CD207的表达下调,提示CA表皮中LC可能出现了数目的减少及功能的受损.     

Expression of CD34 and bcl-2 in phyllodes tumours, fibroadenomas and spindle cell lesions of the breast

AIMS: Strong expression of CD34 and bcl-2 has been described in solitary fibrous tumours. It has been proposed that these lesions arise from long-lived mesenchymal cells. We tested the hypothesis that spindle cell lesions of the breast arise from similar mesenchymal cells in the mammary stroma. METHODS and RESULTS: Sections of phyllodes tumours (26), fibroadenomas (15), myofibroblastomas (two), pseudoangiomatous hyperplasia (five) and myoid hamartoma (one) were stained immunohistochemically for CD34 and bcl-2. Conventional mammary carcinoma is known to be CD34-negative: we therefore stained 11 spindle cell carcinomas and one adenosquamous carcinoma. The mammary stroma, particularly around lobules, stained for CD34. All the lesions (except the carcinomas) showed spindle cell staining for CD34. There was more staining in fibroadenomas than in phyllodes tumours (especially malignant tumours). The staining in phyllodes tumours was typically patchy. In some there was increased or decreased staining adjacent to the epithelium. There were occasional spindle cells positive for bcl-2 in the normal perilobular stroma. bcl-2 was frequently expressed in spindle cells in fibroadenomas, phyllodes tumours and pseudoangiomatous hyperplasia, and rarely in the other lesions. CONCLUSIONS: The combined expression of CD34 and bcl-2 suggests that fibroadenomas, phyllodes tumours and pseudoangiomatous hyperplasia may arise from long-lived bcl-2-positive mesenchymal cells in the breast in a manner similar to that proposed for solitary fibrous tumours. The absence of CD34 staining in spindle cell carcinomas is of potential diagnostic value in the distinction from malignant phyllodes tumours in difficult cases.