20q13.2 Amplification in intraductal hyperplasia adjacent to in situ and invasive ductal carcinoma of the breast

The 20q13 region harboring recently described putative oncogenes is frequently amplified in invasive ductal carcinoma (IDC). The aim of this study was to examine the 20q13 copy number in intraduct hyperplasia (IH), atypical duct hyperplasia (ADH), and ductal carcinoma in situ (DCIS) adjacent to IDC. In 5 patients, comparative genomic hybridization (CGH) after laser microdissection revealed 20q13 amplification in four of five cases of IH, in all of three cases of IH with atypia, all five of DCIS, and all five of IDC. Fluorescence in situ hybridization (FISH) confirmed the amplification at 20q13.2 in IH in the two specimens analyzed. The amplification rate, however, was higher in DCIS and IDC. In phenotypically normal ductal epithelium normal values were found for 20q13 copy number by FISH (n=2) and CGH (n=5). Although the number of cases presented here is small, our results suggest that mutations in the 20q13.2 region in IH may be associated with accelerated proliferation and hyperplasia of the ductal epithelium. Progression to DCIS and ICD is accompanied by a further increase in the 20q13.2 copy number. Received: 17 March 1999 / Accepted: 22 June 1999     

乳腺癌和乳腺导管内增生性病变Notch1基因甲基化的检测及临床意义

Objective To explore the relevance between the promoter methylation status of Notch1gene and the invasive ductal carcinoma and ductal hyperplastic lesions of the breast.Methods Methylation status of Notch1 gene in human breast invasive ductal carcinoma(IDC,n=89),ductal carcinoma in situ (DOS,n=20),atypical ductal hyperplasia(ADH,,n=11)and usual ductal hyperplasia(UDH,n=20)were quantitatively evaluated by MALDI-TOF MS.The expression of Notch1 protein was detected by immunohistochemical stain(SP method).Results Positive expression rates of Notch1 protein in IDC and DCIS were 91.0%(81/89)and 75.0%(15/20),respectively,which were significandy higller than those 0f ADH(4/11)and UDH(30.0%.6/20;P＜0.05).Notch1 protein expression was correlated significantly with lymph node metastasis,pathological grades and TNM stages of IDC.The mean methylation levels of Notch1 gene at CpG_3,CpC 4.5 and CpG_8 significantly decreased in IDC group compared with those of DCIS.ADH and UDH groups(P＜0.0083).In breast carcinomas, the mean methylation rates of Notch1 gene at CpG-4.5,CpG-10.11,and CpG_14.15.16 loci in cases with axillary node metastasis were significantly lower than those without axillary node metastasis(P＜0.05):and the methylation rates at CpG_14.15.16 and CpG_18 lociin stage Ⅰ were lower than that in stage Ⅱ,further lower than that in stage Ⅲ(P＜0.05);and that in CpG_1.2,CpG_12.13 loci in grade Ⅰ(highly-differentiated group)were higher than that in grade Ⅱ(moderate-differentiated group)and grade Ⅲ(peody-differentiated group) (P＜0.05);and the methylation rates at CpG_3,CpG_8 and CpG_14.15.16 loci in ER+ PR+ HER2-group were lower than that in ER-PR-HER2+ group(P＜0.05).Conclusions There is an overall hypomethylation of Notch1 gene in breast invasive ductal carcinomas with corresponding over-expression of Notehl protein.This inverse correlation show that the alteration of protein expression result from hypomethylation oncogene Notch1,and this change may have important significance in breast tumorigenesis and the development.Specific hypomethylation at CpG_3,CpG_4.5 and CpG_8 loci of Notehl gene may play a role in the pathogenesis of breast carcinoma,suggesting the progression and/or malignant transformation from benign glandular lesions of the breast.     

乳腺癌和乳腺导管内增生性病变Notch1基因甲基化的检测及临床意义

目的 探讨Notch1基因甲基化与乳腺浸润性导管癌(IDC)及乳腺导管内增生性病变的相关性.方法 用基质辅助激光解析电离时间飞行质谱仪(MALDI-TOF MS)对89例乳腺IDC、20例导管原位癌(DCLS)、11例不典型导管增生(ADH)及20例普通型导管增生(UDH)组织进行Notch1基因甲基化的定量检测.采用...     

Expression of c-erbB-2 in in situ and in adjacent invasive ductal adenocarcinomas of the female breast.

Several lines of evidence have demonstrated that expression of the c-erbB-2 gene product contributes to the malignant phenotype. We and others have determined that c-erbB-2 is substantially expressed in most ductal in situ carcinomas of the comedo type, but not in other patterns of ductal carcinoma in situ or in atypical ductal hyperplasia of the breast. In the present investigation, by immunohistochemistry we inquired whether invasive ductal adenocarcinomas retained the c-erbB-2 expression status of the in situ carcinomas from which they derived. Of twelve specimens containing both cribriform/micropapillary in situ and derivative invasive adenocarcinomas in the same section, all tumor cells were negative for c-erbB-2 expression. In thirteen in situ carcinomas of the comedo type, with identifiable invasive components, ten had definite c-erbB-2 expression, and in every case there was comparable c-erbB-2 protein staining of in situ and invasive components; in three of these ten cases the staining in the in situ component tended to be more intense. These findings imply that a significant proportion of invasive mammary adenocarcinomas expressing c-erbB-2 protein is derived from ductal in situ carcinomas of the comedo type.     

Mechanisms of progression of ductal carcinoma in situ of the breast to invasive cancer. A hypothesis

Ductal carcinoma in situ (DCIS), a known precursor lesion of invasive cancer of the female breast, is surrounded by a thick basement membrane and a layer of myoepithelial cells. For DCIS to become invasive, both these barriers must be breached by cancer cells. It has been repeatedly suggested that proteolytic enzymes are somehow involved in this process but a direct proof of this event has never been provided. It is our hypothesis that invasion of the DCIS by capillary vessels derived from the periductal necklace of vessels is the most likely mechanism of breaching the basement membrane, providing an escape hatch for cancer cells. This hypothesis was initially tested on ten randomly selected cases of DCIS, with or without invasion. Capillary vessels were visualized by staining histologic sections with an antibody to CD 34 and, in three cases, by combined stain for CD 34 and collagen IV. In five of the 10 cases of DCIS, the presence of discrete capillary vessels invading DCIS could be documented. In two of these five cases, the vessels subdivided the cancerous ducts into territories of unequal sizes. Vascular invasion of DCIS is a plausible mechanism of breaching the basement membrane in DCIS as a prelude to invasion. This hypothesis must be further tested on a much larger number of cases. The hypothesis, if confirmed, may suggest that invasive cancer derived from DCIS may be prevented by antiangiogenic therapy.     

The status of cyclooxygenase-2 expression in ductal carcinoma in situ lesions and invasive breast cancer correlates to cyclooxygenase-2 expression in normal breast tissue

OBJECTIVES: There is a paucity of data on cyclooxygenase (COX)-2 expression in normal breast tissue and on the changes in COX-2 expression from normal tissue via ductal carcinoma in situ (DCIS) lesions to invasive cancer. The aim of this study, therefore, was to investigate COX-2 protein expression in normal breast tissue, DCIS, and invasive breast cancer in samples from the same patients. METHODS: In 39 patients, we investigated and compared COX-2 expression in paired samples of invasive cancer and normal adjacent breast epithelium by immunohistochemistry with a monoclonal COX-2 antibody. Furthermore, in 29 of these cases, we also analyzed a concomitant DCIS lesion. RESULTS: Patients without COX-2 expression in normal breast tissue also do not express COX-2 in invasive breast cancer and in DCIS lesions, respectively. Conversely, COX-2 expression in normal breast tissue was an indicator for COX-2 expression in the paired breast tumors. There was no significant correlation between COX-2 expression and pathologic tumor stage, nodal status, hormone receptor status, tumor size, grading, and lymphovascular space involvement. CONCLUSIONS: This is the largest study to date investigating COX-2 in paired samples of breast tumors and normal adjacent breast tissue. Our data are consistent with the hypothesis that COX-2 overexpression is an early event in breast carcinogenesis.     

基底型细胞角蛋白在乳腺导管内增生性病变诊断中的应用

目的比较不同类型基底型细胞角蛋白(CK5、CK34βE12和CK14)在乳腺导管内增生性病变中的辅助诊断价值,并结合肌上皮标记、超微电镜对普通型导管增生的细胞成分进行初步分析。方法参照2003年WHO乳腺疾病分类的诊断标准筛选出28例导管普通型增生(UDH)、10例不典型增生(ADH)和25例导管原位癌(DCIS)。所有病例均进行CK5/6、CK34βE12、CK14、CK8、浕SMA、calponin和p63的免疫组化染色。4例UDH和1例DCIS通过电镜观察其增生细胞的超微结构。结果CK5/6在UDH、ADH和DCIS增生细胞中的阳性表达率分别为92.9%、10.0%和0。CK34βE12和CK14的阳性表达率分别为96.4%和82.1%(UDH)、20.0%和30.0%(ADH)、24.0%和28.0%(DCIS)。所有UDH的增生细胞均不表达浕SMA、calponin和p63。电镜观察显示UDH和DCIS的增生细胞中未发现符合肌上皮超微特征的细胞存在。结论基底型CK有助于UDH和ADH/DCIS的鉴别诊断,其中CK5/6较CK34βE12和CK14特异性更高。免疫组化染色和电镜观察结果支持UDH的增生细胞含有多种成分,包括定向干细胞、腺中间细胞和腺终端细胞等,但未发现具有肌上皮特点的细胞参与其中。     

乳腺癌切除标本内导管内增生性病变的免疫表型观察

目的探讨乳腺癌切除标本内导管内增生性病变的形态和免疫表型特点及其与浸润癌的关系。方法筛选出浸润性导管癌切除标本内有较多癌旁组织的病例36例和同期乳腺良性病变28例(对照组),选用CK5、CK34βE12、S100蛋白、SMA、CK8、Ecad、cerbB2等7种抗体做免疫组化染色。结果乳癌组36例中28例伴导管内增生性病变,单纯或复合出现的病变包括:普通性导管增生7例,柱状细胞病变12例,不典型导管增生4例,导管原位癌24例,伴两种以上病变者10例,4种病变同时存在者2例。对照组中计普通性导管增生23例,柱状细胞病变9例。免疫组化提示CK5在旺炽型UDH中腺系上皮细胞有大量表达,不典型导管增生、导管原位癌及浸润性导管癌中其表达明显降低直至完全失表达;CK34βE12表达类似于CK5,但较CK5为强,二者并不完全重合;S100蛋白表达于肌上皮细胞和增生的腺系上皮细胞,其在UDH的腺系上皮中的表达近似于CK34βE12,却不表达SMA;在24例高级DCIS中,11例肌上皮对S100蛋白的反应性先消失,但对SMA仍呈强反应;Ecad在导管原位癌、浸润性导管癌中出现再表达和(或)阳性等级升高;cerbB2在高级DCIS和IDC中呈清晰的膜表达。结论77.87%浸润性导管癌伴有不同的导管内增生性病变,这些病变不仅形态学表现不同,且免疫表型有异,可据此协助诊断与鉴别诊断。仅据对活检诊断的导管内增生性病变患者长期随访而得出的后来发生浸润性乳腺癌危险度的结论,与当初诊断的病变并无直接相关,而更可能与当初残留或后来发生的导管内增生性病变有关。     

Cytological criteria for the diagnosis of intraductal hyperplasia, ductal carcinoma in situ, and invasive carcinoma of the breast

The advent of mammography screening presents a diagnostic challenge to the cytopathologist as an increasing proportion of breast lesions requiring investigation will be nonpalpable and up to 40% will be accounted for by atypical intraductal hyperplasia and ductal carcinoma in situ, as opposed to previously, when these lesions represented less than 10% of palpable tumors. We studied 133 fine-needle aspirates from breast tumors and found that nuclear morphology, myoepithelial cells, signs of invasion, and degree of cellular dissociation are among the most potent factors discriminating between benign epithelial proliferations, atypical intraductal hyperplasia, ductal carcinoma in situ, and invasive carcinoma.     

Lymphoreticular infiltrates in invasive ductal breast cancer

Summary Fifty-two invasive ductal breast cancers were investigated histologically and immunohistologically to assess localization and composition of the lymphoreticular infiltrates. The tumour-infiltrating cells were mainly located in the intervening stroma, whereas tumour foci often exhibited lower numbers of lymphoreticular cells. Macrophages (Mono 1+ and KiM 6+) and helper/inducer cells bearing the T4 surface antigen (Leu-3a+) regularly constituted the majority of the tumour-infiltrating lymphoreticular cells. In more than 80% of cases large numbers of macrophages were found, and many T4 cells occured in about 60%. Next in frequency were the T lymphocytes (Leu-1+) which were mostly observed in high (46%), or in moderate (39%) numbers. In about 2/3 of the cases moderate numbers of T8 (suppressor/cytotoxic) lymphocytes (Leu-2a+) were detected. B lymphocytes (T0 15+) and natural killer cells (Leu-7+) were generally encountered in very low numbers, while eosinophilic granulocytes were virtually absent from the lymphoreticular infiltrates. Tissue mast cells and plasma cells were present in very low numbers in about one half of the tumours but cases with low, moderate or - rarely - even high numbers of infiltrating cells also occured. It must be emphasized that an in situ histomorphological analysis of the cellular part of the stromal reaction of invasive ductal breast cancers allows only limited conclusions concerning the functional properties of the tumour-infiltrating lymphoreticular cells. From the present study, macrophages and T4 cells but also T8 lymphocytes might be of significance in immunooncological reactions against clinically detectable stages of invasive breast cancer.This work is dedicated to Prof. Dr.Dr.h.c. K. Lennert in honor of his 65. birthday.Supported by the Schleswig-Holsteinische Krebsgesellschaft e.V. and the Tumorzentrum Kiel e.V.     

HER2 status in pure ductal carcinoma in situ and in the intraductal and invasive components of invasive ductal carcinoma determined by fluorescence in situ hybridization and immunohistochemistry

AIM: To determine the HER2 status of ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC) of the breast. The increased prevalence of HER2 amplification and overexpression in DCIS is considered to be maintained in the intraductal component of IDC; however, HER2 amplification and overexpression are detected much less in IDC. METHODS AND RESULTS: Fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) were performed to detect HER2 in 270 IDCs with an intraductal component and in 50 pure DCIS samples; IHC was also performed in 116 metastatic nodes. HER2 was found to be amplified in 77 cases (28.5%) and overexpressed in 79 (29.3%) of the 270 IDCs. HER2 amplification was similar between intraductal and invasive components of the same tumour. The concordance for HER2 status between invasive and intraductal components of individual tumours was 98.5% and 99.3% by FISH and IHC, respectively. HER2 was amplified in 25 (50%) of the 50 pure DCIS samples. HER2 overexpression in metastatic nodes resembled the HER2 status in the primary tumour for 108 (93.1%) of 116 cases (kappa =0.831). CONCLUSION: Our study indicates that the intraductal component of IDC may differ biologically when compared with pure DCIS. HER2 appears to lack a critical role in the progression from DCIS to IDC and HER2 status is maintained in metastatic lesions.     

Similarity in expression of cell cycle proteins between in situ and invasive ductal breast lesions of same differentiation grade.

There is increasing evidence that there are different progression routes leading to invasive breast cancer, depending on histology and differentiation grade. The aim of this study was to determine alterations in the expression of proteins involved in proliferation and apoptosis in non-invasive and invasive ductal breast lesions. Immunohistochemistry was performed on 106 usual ductal hyperplasias (UDH), 61 DCIS lesions and 53 invasive ductal breast carcinomas. Increased proliferation (Ki67), overexpression of cyclin D1, HER-2/neu, p21 and p53, and decreased expression of bcl-2 and p27 could already be found in UDH. Significant differences between UDH and DCIS lesions were found for only one protein when UDH was compared with well-differentiated DCIS (p27), for three proteins when compared with intermediately differentiated DCIS (p21, cyclin D1, Ki-67), and for all proteins when compared with poorly-differentiated DCIS. Comparing DCIS with invasive lesions of same differentiation grade, proliferation was elevated in the invasive lesions. Altered expression of the other proteins was in general only slightly increased in the invasive lesion compared with DCIS. The number of proteins with altered expression per lesion was highest in poorly-differentiated lesions and was comparable between DCIS and invasive cancer of the same differentiation grade. In conclusion, the biggest changes in expression of these proliferation and apoptosis related proteins appear to occur during the transition from hyperplasia to DCIS; they probably play a minor role in the transition from DCIS to invasive breast lesion of same differentiation grade. Well-differentiated in situ and invasive breast lesions share many of the aberrations in expression of these proteins, as do poorly-differentiated in situ and invasive lesions. However, there are many differences between the well and poorly-differentiated lesions. This further supports the existence of different progression routes leading to breast cancer.     

细胞角蛋白在乳腺导管内增生性病变鉴别诊断中的应用

目的 研究细胞角蛋白(CK)在乳腺导管内增生性病变的表达情况,寻求帮助乳腺导管内增生性病变鉴别诊断的分子标记。方法 按Page标准选病例,收集本院1993～2002年病理标本,乳腺导管内增生性病变92例(石蜡包埋标本)、冷冻切片30例以及导管上皮普通性增生原代培养上皮细胞和浸润性导管癌细胞株T-47D和MCF-7。采用EnVision标准二步法研究CK34βE12、CK8以及CK14表达情况。结果 (1)石蜡组织中CK34βE12在导管上皮普通性增生、不典型性增生、导管原位癌以及浸润性导管癌的阳性结果分别为95．2％、33．3％、19．2％和12．5％;导管上皮普通性增生、浸润性导管癌的冷冻切片CK34βE12阳性率为100％和55％;CK34βE12在MCF7呈阴性染色,在普通性增生原代培养细胞及T-47D中呈阳性染色;(2)CK8与CK14在乳腺导管上皮普通性增生的表达模式与其他病变不同。结论 CK34βE12有助于乳腺导管内增生性病变的鉴别诊断,但还不适用于术中冷冻快速诊断;CK8与CK14在乳腺导管内增生性病变中的表达模式可有助于鉴别诊断。     

Myoepithelial cell staining patterns of papillary breast lesions: from intraductal papillomas to invasive papillary carcinomas

We evaluated 25 intraductal papillomas and 18 papillary carcinomas (invasive, 4; micropapillary ductal carcinoma in situ [DCIS], 5; cases originally classified as intracystic/intraductal papillary carcinoma, 9) by calponin, smooth muscle myosin heavy chain (SMM-HC), and p63 immunostains. Calponin, SMM-HC, and p63 labeled myoepithelial cells (MECs) in all intraductal papillomas and all micropapillary DCIS cases. The invasive papillary carcinoma cases were uniformly negative for all stains. The 9 cases originally diagnosed as intracystic/intraductal papillary carcinoma showed more variable results, with identification of an MEC layer in only 4 cases. Comparison of staining of MECs by these 3 stains showed that calponin was more sensitive and intense than SMM-HC; however, there was cross-reactivity with myofibroblastic cells. Staining with p63 was discontinuous, making interpretation of an intact myoepithelial layer difficult. Of 9 cases originally classified as intraductal papillary carcinoma, 5 showed absence of a basal MEC layer by immunohistochemical analysis. The lack of a basal MEC layer in these cases suggests a spectrum of progression from in situ to invasive disease and might help explain distant metastases from previously reported "intraductal papillary carcinoma."     

Lysyl oxidase gene expression in the stromal reaction to in situ and invasive ductal breast carcinoma.

Lysyl oxidase is involved in the main pathway of collagen and elastin cross-linking: it has a role in the maturation of fibrillar matrix proteins in fibrosing processes and dictates their stability against metalloproteases. The stromal reaction patterns in ductal breast carcinoma are known to be morphologically varied. This has raised the hypothesis that there might be a differential expression of the lysyl oxidase gene as a function of stromal reaction pattern. The present study investigates this potential correlation and the role of matrix protein cross-linking in stromal differentiation. Lysyl oxidase was detected by immunohistochemistry and lysyl oxidase gene expression by in situ hybridization. Maximal expression was observed in myofibroblasts and myoepithelial cells around in situ tumors and in the reactive fibrosis facing the invasion front of infiltrating tumors. The lysyl oxidase substrates were observed in parallel, resulting in the stabilization of a scar-like peritumor barrier. In contrast, a lack of lysyl oxidase was associated with the loose or scirrhous stroma accompanying invading tumors; here, in situ hybridization revealed type I collagen synthesis, resulting in the deposition of non-cross-linked matrix proteins susceptible to degradation. The early development of a cross-linked matrix around ductal breast carcinoma suggests a possible bost defense mechanism, whereas the synchronous or late stromal reaction lacking lysyl oxidase favors tumor dispersion.     

Genomic imbalances detected by comparative genomic hybridization are prognostic markers in invasive ductal breast carcinomas

Genomic imbalances detected by comparative genomic hybridization are prognostic markers in invasive ductal breast carcinomas
Aims : The aim of this work is the study of the prognostic significance of the chromosomal aberrations described in a series of invasive ductal breast carcinomas.
Methods and results : We analysed by comparative genomic hybridization a group of 70 formalin-fixed paraffin-embedded invasive ductal breast carcinomas. Aberrations showed a frequency similar to previous studies using frozen tumours. Interestingly, we identified gains involving 6q16-q24 more frequently than in other series. We analysed the association among the chromosomal imbalances, 11 histopathological factors, relapse rate and overall survival of patients. Associations showed 16q losses as a potential marker of good prognosis, as they were more frequent in node-negative ( P =0.025) and in oestrogen-positive tumours ( P  < 0.001). Furthermore, 100% of bcl-2+ tumours presented this aberration compared with 29.3% in bcl-2– ( P =0.014). 1q, 11q, 17q and 20q gains were associated with poor prognosis: 95% of cases with 1q gains were bigger than 20 mm ( P =0.041). Tumours with 1q and 11q gains showed a higher relapse rate ( P =0.063; P =0.066). Within the good prognosis group of lymph node-negative patients, 17q and 20q gains identify a subgroup with increased relapse rate ( P =0.039).
Conclusions : Chromosomal imbalances, together with histopathological factors, may help to predict outcome in breast cancer patients.     

A dilutional immunoperoxidase study of proliferative ductal lesions and carcinomata of the breast

A dilutional immunoperoxidase study of carcinoembryonic antigen (CEA) reactivity of mild and severe epitheliosis as well as malignant ductal and lobular lesions of the breast was performed. Intraduct carcinoma with a cribriform and clinging patterns showed intracytoplasmic, glycocalyceal and intraluminal staining for CEA at higher dilutions of antiserum than cases with mild and severe epitheliosis. Also, many intraduct carcinomas associated with infiltration stain at a lower concentration of antiserum to CEA than pure intraduct lesions. Staining is seen at lowest concentrations in the infiltrating components. This suggests that as intraduct carcinoma becomes invasive, it loses some of its ability to store and possibly to synthesize CEA. The dilutional immunoperoxidase method could be applied routinely to cases of severe epitheliosis to differentiate them from intraduct carcinoma. However, relatively few cases were studied in this preliminary series and a further study is being carried out. The difficulties encountered using CEA as a tumour marker are outlined.     

Genomic and mutational profiling of ductal carcinomas in situ and matched adjacent invasive breast cancers reveals intra-tumour genetic heterogeneity and clonal selection

The mechanisms underlying the progression from ductal carcinoma in situ (DCIS) to invasive ductal carcinoma (IDC) of the breast are yet to be fully elucidated. Several hypotheses have been put forward to explain the progression from DCIS to IDC, including the selection of a subpopulation of cancer cells with specific genetic aberrations, and the acquisition of new genetic aberrations or non-genetic mechanisms mediated by the tumour microenvironment. To determine whether synchronously diagnosed ipsilateral DCI and IDCs have modal populations with distinct repertoires of gene copy number aberrations and mutations in common oncogenes, matched frozen samples of DCIS and IDC were retrieved from 13 patients and subjected to microarray-based comparative genomic hybridization (aCGH) and Sequenom MassARRAY (Oncocarta v 1.0 panel). Fluorescence in situ hybridization and Sanger sequencing were employed to validate the aCGH and Sequenom findings, respectively. Although the genomic profiles of matched DCI and IDCs were similar, in three of 13 matched pairs amplification of distinct loci (ie 1q41, 2q24.2, 6q22.31, 7q11.21, 8q21.2 and 9p13.3) was either restricted to, or more prevalent in, the modal population of cancer cells of one of the components. Sequenom MassARRAY identified PIK3CA mutations restricted to the DCIS component in two cases, and in a third case the frequency of the PIK3CA mutant allele reduced from 49% in the DCIS to 25% in the IDC component. Despite the genomic similarities between synchronous DCIS and IDC, our data provide strong circumstantial evidence to suggest that in some cases the progression from DCIS to IDC is driven by the selection of non-modal clones that harbour a specific repertoire of genetic aberrations.