Multiple Fluorescence In Situ Hybridization Research Articles

Multiple Fluorescences in Situ Hybridization Status in Excreted Urine Improve Diagnostic Efficacy for Upper Urinary Tract Urothelial Carcinomas.

To evaluate the diagnostic accuracy of single and multiple fluorescence in situ hybridization (FISH) tests for upper urinary tract cancer (UTUC), we analyzed the diagnostic efficacy of FISH in patients with UTUC and the difference between it and the Tumor Node Metastasis (TNM) stage and grade of the tumor. Patients treated for UTUC at our institution between 2011 and 2021 who had not been previously diagnosed with UTUC were included. Patients were divided into single, two, and multiple (three times or four times) FISH groups based on the number of FISH tests performed on different samples from the same patient, and the diagnostic efficiency of single, two, and multiple FISH tests for muscle-invasive tumors and highgrade tumors were assessed. We included a total of 207 patients with UTUC, and when compared to single FISH, the sensitivity of multiple and double FISH for the diagnosis of UTUC increased from 62% to 76% and 78%, respectively. It went from 67% to 78% and 80% for muscle-invasive UTUC (> = pT2) and from 71% to 79% and 81% for the highest- grade UTUC. Multiple FISH improves the diagnostic efficacy of UTUC and helps to differentiate aggressive tumors.

Coral holobiont research needs spatial analyses at the microbial scale.

Coral holobiont research needs spatial analyses at the microbial scale.

Multi-probe FISH Analysis of Immunophenotyped Chronic Lymphocytic Leukemia by Imaging Flow Cytometry.

Imaging flow cytometry is an automated method that enables cells and fluorescent signals to be visualized and quantified. Here, we describe a new imaging flow cytometry method whereby fluorescence in situ hybridization (FISH) is integrated with cell phenotyping. The method, called "immuno-flowFISH," provides an exciting new dimension for the analysis of genomic changes in cytological samples (e.g., blood, bone marrow). Cells are analyzed in suspension without any requirement for prior cell isolation or separation. Multiple antibodies and FISH probes, each with a unique fluorophore, can be added and many thousands of cells analyzed. Specific cell populations are identified by their antigenic profile and then analyzed for the presence of chromosomal defects. Immuno-flowFISH was applied to the assessment of chronic lymphocytic leukemia (CLL), a mature B-cell neoplasm where chromosomal abnormalities predict prognosis and treatment requirements. This integrated immunophenotyping and multi-probe FISH strategy could detect both structural and numerical chromosomal changes involving chromosomes 12 and 17 in CLL cells. Given that many thousands of cells were analyzed and the leukemic cells were positively identified by their immunophenotype, this multi-probe method adds precision to the cytogenomic analysis of CLL. © 2021 Wiley Periodicals LLC.

RET Fluorescence In Situ Hybridization Analysis Is a Sensitive but Highly Unspecific Screening Method for RET Fusions in Lung Cancer

IntroductionRET gene fusions are established oncogenic drivers in 1% of NSCLC. Accurate detection of advanced patients with RET fusions is essential to ensure optimal therapy choice. We investigated the performance of fluorescence in situ hybridization (FISH) as a diagnostic test for detecting functional RET fusions. MethodsBetween January 2016 and November 2019, a total of 4873 patients with NSCLC were routinely screened for RET fusions using either FISH (n = 2858) or targeted RNA next-generation sequencing (NGS) (n = 2015). If sufficient material was available, positive cases were analyzed by both methods (n = 39) and multiple FISH assays (n = 17). In an independent cohort of 520 patients with NSCLC, whole-genome sequencing data were investigated for disruptive structural variations and functional fusions in the RET and compared with ALK and ROS1 loci. ResultsFISH analysis revealed RET rearrangement in 48 of 2858 cases; of 30 rearranged cases double tested with NGS, only nine had a functional RET fusion. RNA NGS yielded RET fusions in 14 of 2015 cases; all nine cases double tested by FISH had RET locus rearrangement. Of these 18 verified RET fusion cases, 16 had a split signal and two a complex rearrangement by FISH. By whole-genome sequencing, the prevalence of functional fusions compared with all disruptive events was lower in the RET (4 of 9, 44%) than the ALK (27 of 34, 79%) and ROS1 (9 of 12, 75%) loci. ConclusionsFISH is a sensitive but unspecific technique for RET screening, always requiring a confirmation using an orthogonal technique, owing to frequently occurring RET rearrangements not resulting in functional fusions in NSCLC.

14. A novel cytogenomic approach to diagnosis of plasma cell neoplasms

Plasma cell neoplasm (PCN) is characterized by specific chromosomal aberrations with diagnostic and prognostic significance. Low percentage of neoplastic cells is a drawback in application of karyotyping and fluorescence in situ hybridization (FISH) for evaluation of bone marrow aspirates. Enrichment techniques to isolate the CD138+ cells have improved the detection rates. However, a complete FISH analysis for various abnormalities may not be achieved due to limited number of isolated cells. In 2017, we validated and implemented a novel approach for a whole genome profiling of plasma cells in PCN. The protocol consisted of isolation of CD138+ cells, whole genome DNA amplification and microarray comparative genomic hybridization. Separate FISH analysis was performed for detection of balanced IGH rearrangements. Of 412 clinical cases to date, 234 (56.8%) had morphologic and immunohistochemical studies indicative of PCN with 0.5–90% plasma cells in a bone marrow aspirates. Among PCN patients, chromosomal abnormalities were identified in 223 (95.2%) demonstrated by both microarray and FISH (n = 76, 32.9%), microarray (n = 116, 50.2%) or FISH only (n = 31, 13.9%). The most common findings included IGH rearrangement (49%), 13q deletion (45%), hyperdiploidy (41%), and 1q duplication (38%). Tetraploidy and MYC rearrangements were observed in 2.1% (5/234) and 1.7% (4/234) of patients, respectively. Interestingly, microarray revealed characteristic deletions involving the 6q21q25 region in 4/7 patients with Waldenström Macroglobulinemia. Our diagnostic approach to PCN is a cost-efficient replacement of multiple FISH assays that provides a superior detection rate and additional information for disease classification, prognosis, treatment and differentiation from other B cell malignancies.

Role of fluorescence in situ hybridization in diagnosing cholangiocarcinoma in indeterminate biliary strictures.

Brush cytology, the conventional method to diagnose cholangiocarcinoma, has been plagued by low diagnostic sensitivity and false-negative results. This paper aims to study the clinical utility of fluorescence in situ hybridization (FISH) in enhancing identification of malignant biliary strictures. Brush cytologic specimens collected from endoscopic retrograde cholangiopancreatography for biliary strictures in a tertiary hospital in Singapore from March 2013 to July 2015 were examined by FISH technique using UroVysion probe set in this study. Thirty patients were chosen with five patients having multiple FISH performed due to indeterminate results. The diagnoses for biliary strictures were 13 (43.3%) cholangiocarcinomas, seven (23.3%) pancreatic cancers, seven (23.3%) benign biliary strictures, and three (10%) primary sclerosing cholangitis. Conventional brush cytology had sensitivity of 53.8% with specificity of 82.4%. FISH had sensitivity of 30.8% with specificity of 100%. When FISH results were interpreted in cases with negative or atypical brush cytology, two patients had positive FISH results and cholangiocarcinomas. Based on this pilot study, FISH increased sensitivity of brush cytology in detection of cholangiocarcinoma from 53.8% to 69.2% while preserving specificity of 82.4%. Compared with conventional cytology with low sensitivity, FISH may help to increase sensitivity on top of brush cytology while maintaining high specificity.

Phylogenetic analysis of multiple FISH markers in oral tongue squamous cell carcinoma suggests that a diverse distribution of copy number changes is associated with poor prognosis.

Oral tongue squamous cell carcinoma (OTSCC) is associated with poor prognosis. To improve prognostication, we analyzed four gene probes (TERC, CCND1, EGFR and TP53) and the centromere probe CEP4 as a marker of chromosomal instability, using fluorescence in situ hybridization (FISH) in single cells from the tumors of sixty-five OTSCC patients (Stage I, n = 15; Stage II, n = 30; Stage III, n = 7; Stage IV, n = 13). Unsupervised hierarchical clustering of the FISH data distinguished three clusters related to smoking status. Copy number increases of all five markers were found to be correlated to non-smoking habits, while smokers in this cohort had low-level copy number gains. Using the phylogenetic modeling software FISHtrees, we constructed models of tumor progression for each patient based on the four gene probes. Then, we derived test statistics on the models that are significant predictors of disease-free and overall survival, independent of tumor stage and smoking status in multivariate analysis. The patients whose tumors were modeled as progressing by a more diverse distribution of copy number changes across the four genes have poorer prognosis. This is consistent with the view that multiple genetic pathways need to become deregulated in order for cancer to progress.

Semi-comprehensive analysis of gene amplification in gastric cancers using multiplex ligation-dependent probe amplification and fluorescence in situ hybridization

The prognosis of patients with gastric carcinomas at an advanced stage still remains dismal, and therefore novel therapeutic modalities are urgently needed. Since the successful targeting of amplified ERBB2 with a humanized monoclonal antibody, the amplified genes of other receptor tyrosine kinases such as EGFR, FGFR2, and MET, as well as those of other cell regulator genes, are being considered as candidate targets of molecular therapy. The aim of the present study was to determine the amplification status of 26 genes, which are frequently amplified in solid cancers, in advanced gastric cancers. A total of 93 formalin-fixed and paraffin-embedded advanced gastric cancer tissues were examined by multiple ligation-dependent probe amplification, and 32 cases with ‘gain’ or ‘amplified’ status of 16 genes were further examined for the respective gene amplification by fluorescence in situ hybridization (FISH) and for the respective protein overexpression by immunohistochemistry. The frequencies of gene amplifications in advanced gastric cancers were as follows: ERBB2 (13 cases, 14%), FGFR2 (7 cases, 8%), MYC (7 cases, 8%), TOP2A (7 cases, 8%), MET (4 cases, 4%), MDM2 (4 cases, 4%), CCND1 (3 cases, 3%), FGF10 (2 cases, 3%), and EGFR (1 case, 1%). Amplification of the receptor tyrosine kinases genes occurred in a mutually exclusive manner except for one tumor in which ERBB2 and FGFR2 were both amplified but in different cancer cells. Co-amplification of ERBB2 and MYC, and EGFR and CCND1, in single nuclei but on different amplicons, was confirmed in one case each. Attempts at correlating the FISH status with the immunohistochemical staining pattern showed variable results from complete concordance to no correlation. In conclusion, combination of multiple ligation-dependent probe amplification and FISH analysis is a feasible approach for obtaining the semi-comprehensive genetic information that is necessary for personalized molecular targeted therapy.

Standardization of fluorescence in situ hybridization studies on chronic lymphocytic leukemia (CLL) blood and marrow cells by the CLL Research Consortium

Five laboratories in the Chronic Lymphocytic Leukemia (CLL) Research Consortium (CRC) investigated standardizing and pooling of fluorescence in situ hybridization (FISH) results as a collaborative research project. This investigation used fixed bone marrow and blood cells available from previous conventional cytogenetic or FISH studies in two pilot studies, a one-day workshop, and proficiency test. Multiple FISH probe strategies were used to detect 6q-, 11q-, +12, 13q-, 17p-, and IGH rearrangements. Ten specimens were studied by participants who used their own probes (pilot study 1). Of 312 FISH interpretations, 224 (72%) were true-negative, 74 (24%) true-positive, 6 (2%) false-negative, and 8 (3%) false-positive. In pilot study no. 2, each participant studied two specimens using identical FISH probe sets to control for variation due to probe sets and probe strategies. Of 80 FISH interpretations, no false interpretations were identified. At a subsequent workshop, discussions produced agreement on scoring criteria. The proficiency test that followed produced no false-negative results and 4% (3/68) false-positive interpretations. Interpretation disagreements among laboratories were primarily attributable to inadequate normal cutoffs, inconsistent scoring criteria, and the use of different FISH probe strategies. Collaborative organizations that use pooled FISH results may wish to impose more conservative empiric normal cutoff values or use an equivocal range between the normal cutoff and the abnormal reference range to eliminate false-positive interpretations. False-negative results will still occur, and would be expected in low-percentage positive cases; these would likely have less clinical significance than false positive results. Individual laboratories can help by closely following rigorous quality assurance guidelines to ensure accurate and consistent FISH studies in their clinical practice and research.

Multicolor Flow Cytometry Detects Monoclonal Plasma Cells In the Vast Majority of Marrows From Patients with Plasma Cell Disorders Shown to Have Genetic Abnormalities by Fluorescence In Situ Hybridization (FISH)

AbstractAbstract 1896Flow cytometric analysis (FCM) is now considered an essential tool for the identification of malignant hemopoietic and lymphoid cells, and it is particularly useful in evaluating plasma cell clonality to differentiate normal from neoplastic plasma cells (PC). Neoplastic PC typically show loss of CD19 and aberrant expression of markers such as CD56 and CD117, but the demonstration of an expansion of PC containing a single immunoglobulin light chain (monotypic or clonal expansion) is critical for determining the nature of a plasma cell population. Genetic abnormalities are becoming essential markers for prognosis of plasma cell disorders (PCD). Because of the relatively low proliferation or low representation of PC in the sample, FISH rather than conventional cytogenetics is used routinely or the detection of karyotypic abnormalities in PCD and the use of FISH in plasma cell-enriched preparations has improved the sensitivity of detection of genetic abnormalities in these disorders. We wished to determine how often FCM would detect monoclonal cells in marrows with genetic abnormalities observed by FISH. For this purpose, we analyzed marrow samples that were either non-enriched or enriched for PC using immunomagnetic beads for cell separation. From February 2009 until present, we studied marrows sent to our laboratory for diagnostic purposes from 158 patients who either had a clinical or laboratory abnormality suggestive of or consistent with PCD, or their marrows demonstrated immunophenotypic abnormalities of PC. The FCM consisted of a simultaneous determination of surface CD45, CD19, CD38, CD56 and intracytoplasmic kappa and lambda immunoglobulin (Ig) light chains in a single tube, using a Canto II cytometer (BD). Between 105 and 3×105 cells were analyzed in each case. Clonal expansions were detected based on the Ig light chain expression in cells selected as normal or abnormal plasma cells by their surface phenotype. FISH analysis was performed using Abbott probes for CEP 7, CEP 9, CCND1/IgH, RB1, and p53 on both enriched and non-enriched interphase cells. FISH samples were processed according to standard procedures and 200 cells were analyzed for each probe. Plasma cell enrichment was performed by incubating marrow cells with CD138-coated immunomagnetic beads, and isolating them on Miltenyi separation columns using an auto MACS Pro Separator. Of the 158 samples studied, 52 underwent plasma cell enrichment. Enrichment was performed on samples with less than 8% PC as assessed by FCM. The fraction of PC in enriched samples was approximately 10 times greater than those in non-enriched samples. FISH abnormalities were detected in enriched samples from cases that contained as low as 0.04% PC prior to enrichment. The majority of the enriched samples that showed FISH abnormalities exhibited multiple FISH alterations, the most common being additional copies of CEP 7, CEP 9 and CCND1 DNA sequences, and deletion of RB1 and p53. Of the 158 samples, 46 (29%) were found to be polyclonal by FCM and normal by FISH. These included 8 samples enriched for PC. Of the 69 non-enriched samples only 33 (48%) demonstrated FISH abnormalities. Of these abnormal samples, 32 (97%) were monoclonal by FCM. Among the 43 samples that underwent plasma cell enrichment, 37 (86%) demonstrated FISH abnormalities. Of these enriched abnormal samples, 34 (92%) were shown to be monoclonal by FCM. Our results showed that, confirming previous observations, targeted FISH analysis using plasma cell enrichment increases the detection frequency of abnormalities in PCD, which can be found in the majority of cases. This study also showed that FCM detected monoclonality in the vast majority of samples of PCD that demonstrated FISH abnormalities, whether or not they were enriched for PC, validating the clinical utility of FCM in the routine diagnostic evaluation of patients with PCD. Disclosures:No relevant conflicts of interest to declare.

415c: Serial Polysomy Fluorescence in Situ Hybridization (FISH) Results in Patients With Primary Sclerosing Cholangitis (PSC)

Fluorescence in situ hybridization (FISH) on pancreatobiliary brushings has been shown to increase sensitivity over routine cytology for the detection of carcinoma; however, the appropriate role of FISH for patients with PSC is currently unclear. The aim of this study was to investigate the outcome of multiple polysomy FISH results from at least 2 separate endoscopic procedures in patients with PSC.

Cytogenetic mapping of common bean chromosomes reveals a less compartmentalized small-genome plant species

Cytogenetic maps of common bean chromosomes 3, 4 and 7 were constructed by fluorescence in-situ hybridization (FISH) of BAC and a few other genomic clones. Although all clones were selected with genetically mapped markers, mostly with single-copy RFLPs, a large subset of BACs, from 13 different genomic regions, contained repetitive sequences, as concluded from the regional distribution patterns of multiple FISH signals on chromosomes: pericentromeric, subtelomeric and dispersed. Pericentromeric repeats were present in all 11 chromosome pairs with different intensities, whereas subtelomeric repeats were present in several chromosome ends, but with different signal intensities depending on the BAC, suggesting that the terminal heterochromatin fraction of this species may be composed of different repeats. The correlation of genetic and physical distances along the three studied chromosomes was obtained for 23 clones. This correlation suggests suppression of recombination around extended pericentromeric regions in a similar way to that previously reported for plant species with larger genomes. These results indicate that a relatively small plant genome may also possess a large proportion of repeats interspersed with single-copy sequences in regions other than the pericentromeric heterochromatin and, nevertheless, exhibit lower recombination around the pericentromeric fraction of the genome.

De novo proximal duplication of 1(q12q22) in a female infant with multiple congenital anomalies

Reports of small proximal 1q duplications are rare. We report a 1 month-old female who was referred to clinic because she was believed to have features suggestive of Turner syndrome. The patient's dysmorphic features included a prominent nose, low-set and crumpled ears, slightly high palate, short neck, high-pitched cry, mild micrognathia, hypoplastic labia majora, and somewhat deep palmar creases. Traditional G-band chromosome studies of the patient were interpreted as 46,XX,dup(1)(q12q21). To further evaluate the extent of the chromosome 1 duplication, Spectral Karyotyping and a series of six fluorescence in situ hybridization (FISH) probes were utilized. The FISH probes refined the extent of the duplication to involve the region 1(q12q22) indicating the duplicated segment was larger than interpreted by the G-banding studies. This first case of non-mosaic proximal duplication of 1q to be characterized by multiple locus specific FISH probes should allow a more refined delineation of the phenotypic findings and clinical significance associated with this rare chromosomal duplication.

Primary amenorrhea in a woman with a cryptic complex chromosome rearrangement involving the critical regions Xp11.2 and Xq24

To characterize a complex chromosome rearrangement (CCR) previously detected by G-banding in peripheral blood lymphocytes, as 46,X,-2,-11,-22,-X,+mar 1+mar2+mar3+mar4 in a patient with primary amenorrhea. Case report. University faculty of Medicine and hospital. A 36-year-old woman with primary amenorrhea. Fluorescence in situ hybridization (FISH). Use of commercially available M-FISH probe (24 colors simultaneously) and whole chromosome painting probes for chromosomes 2, 11, 22, and X to characterize the CCR. The use of conventional and multiple FISH allowed the redefinition of the CCR, showing a cryptic insertion of chromosome 11 in marker 3 previously suspected by M-FISH. The combination of G-banding and FISH data revealed that four chromosomes and seven breakpoints, including 2q21, 2q31, 11q22.1, 11q22.3, 22q13.3, Xp11.21, and Xq24, were implicated in this CCR. This report confirms the importance of a combination of G-banding and FISH (M-FISH and conventional FISH) techniques to characterize the de novo CCR. These techniques also were useful in defining two possible critical chromosome regions, Xp11.21 and Xq24, in which genes of potential interest for a primary amenorrhea could be located.

WWW.Cell Biology Education

WWW.Cell Biology Education

Spectral karyotyping and multicolor fluorescence in situ hybridization reveal new tumor-specific chromosomal aberrations

Spectral karyotyping (SKY), multiple fluorescence in situ hybridization (M-FISH), cross-species color banding (Rx-FISH), multicolor chromosome banding, and other labeling techniques and strategies have been recent comprehensive technical developments in the field of molecular cytogenetics. The immediate goals of these methods are (1) to reliably characterize complex chromosomal rearrangements present in tumor karyotypes; (2) to screen for new tumor-specific chromosomal aberrations; (3) to improve genetic classification systems of different tumor types in correlation with clinical data, treatment regimens, detection of minimal residual disease, and prognosis; and (4) to identify new target regions for gene identification strategies. We present a brief overview of the different methods, including summaries of numerous published and submitted papers detailing specific cytogenetic aberrations associated with lekemias and lymphomas. To date, 640 tumor cases have been analyzed by SKY, including 410 hematologic malignancies, 146 solid tumors, and 45 mouse tumors.

Spectral karyotyping combined with locus-specific FISH simultaneously defines genes and chromosomes involved in chromosomal translocations

Genes that play roles in malignant transformation have often been found proximate to cancer-associated chromosomal breakpoints. Identifying genes that flank chromosomal reconfigurations is thus essential for cancer cytogenetics. To simplify and expedite this identification, we have developed a novel approach, based on simultaneous spectral karyotyping and fluorescence in situ hybridization (FISH) which, in a single step, can identify gross chromosomal aberrations as well as detect the involvement of specific loci in these rearrangements. Signals for specifically queried genes (FISH probe) were easily detectable in metaphase cells, together with the signals from painted chromosomes (spectral karyotyping probes). The concentration and size of the FISH probes could cover a wide range and still be used successfully. Some of the nucleotide-bound dyes used for the labeling, as Cy3, Spectrum Orange, Alexa 594, Texas Red, and Rhodamine 110, were particularly efficient. More than one gene can be queried in the same metaphase, because multiple FISH probes could be hybridized simultaneously. To demonstrate this technique, we applied it to the myeloma cell line Karpas 620, which has numerous chromosomal rearrangements. The approach that we present here will be particularly useful for the analysis of complex karyotypes and for testing hypotheses arising from cancer gene expression studies. Published 2000 Wiley-Liss, Inc.

Spectral karyotyping combined with locus‐specific FISH simultaneously defines genes and chromosomes involved in chromosomal translocations

Genes that play roles in malignant transformation have often been found proximate to cancer-associated chromosomal breakpoints. Identifying genes that flank chromosomal reconfigurations is thus essential for cancer cytogenetics. To simplify and expedite this identification, we have developed a novel approach, based on simultaneous spectral karyotyping and fluorescence in situ hybridization (FISH) which, in a single step, can identify gross chromosomal aberrations as well as detect the involvement of specific loci in these rearrangements. Signals for specifically queried genes (FISH probe) were easily detectable in metaphase cells, together with the signals from painted chromosomes (spectral karyotyping probes). The concentration and size of the FISH probes could cover a wide range and still be used successfully. Some of the nucleotide-bound dyes used for the labeling, as Cy3, Spectrum Orange, Alexa 594, Texas Red, and Rhodamine 110, were particularly efficient. More than one gene can be queried in the same metaphase, because multiple FISH probes could be hybridized simultaneously. To demonstrate this technique, we applied it to the myeloma cell line Karpas 620, which has numerous chromosomal rearrangements. The approach that we present here will be particularly useful for the analysis of complex karyotypes and for testing hypotheses arising from cancer gene expression studies. Genes Chromosomes Cancer 27:418–423, 2000. Published 2000 Wiley-Liss, Inc.

Amplification of the 11q23 region in acute myeloid leukemia

Cytogenetic abnormalities involving the 11q23 region are found in both acute lymphoblastic leukemia (ALL) and myeloid leukemia (AML). Molecular consequences of 11q23 translocations are the formation of chimeric genes, all of them involving the MLL (mixed-lineage leukemia) gene. To evaluate the usefulness of fluorescence in situ hybridization (FISH) in detecting MLL rearrangements in AML, we analyzed 181 patients with an MLL-specific probe. Among them, we detected three patients with multiple FISH signals, reflecting genomic amplification of this chromosomal region. Extra copies of MLL have been reported previously in four patients, but did not correspond to a true gene amplification. For the first time, we describe genomic amplification of the 11q23 region (up to more than 50 copies) in AML patients. This genomic amplification could affect MLL, but other genes in the vicinity could also be the primary target. Genes Chromosomes Cancer 26:166–170, 1999. © 1999 Wiley-Liss, Inc.

Amplification of the 11q23 region in acute myeloid leukemia

Cytogenetic abnormalities involving the 11q23 region are found in both acute lymphoblastic leukemia (ALL) and myeloid leukemia (AML). Molecular consequences of 11q23 translocations are the formation of chimeric genes, all of them involving the MLL (mixed-lineage leukemia) gene. To evaluate the usefulness of fluorescence in situ hybridization (FISH) in detecting MLL rearrangements in AML, we analyzed 181 patients with an MLL-specific probe. Among them, we detected three patients with multiple FISH signals, reflecting genomic amplification of this chromosomal region. Extra copies of MLL have been reported previously in four patients, but did not correspond to a true gene amplification. For the first time, we describe genomic amplification of the 11q23 region (up to more than 50 copies) in AML patients. This genomic amplification could affect MLL, but other genes in the vicinity could also be the primary target. Genes Chromosomes Cancer 26:166-170, 1999.