Physical mapping of a translocation breakpoint in neurofibromatosis.

The gene for von Recklinghausen neurofibromatosis (NF1), one of the most common autosomal-dominant disorders of humans, was recently mapped to chromosome 17 by linkage analysis. The identification of two NF1 patients with balanced translocations that involved chromosome 17q11.2 suggests that the disease can arise by gross rearrangement of the NF1 locus, and that the NF1 gene might be identified by cloning the region around these translocation breakpoints. To further define the region of these translocations, a series of chromosome 17 Not I-linking clones has been mapped to proximal 17q and studied by pulsed-field gel electrophoresis. One clone, 17L1 (D17S133), clearly identifies the breakpoint in an NF1 patient with a t(1;17) translocation. A 2.3-megabase pulsed-field map of this region was constructed and indicates that the NF1 breakpoint is only 10 to 240 kilobases away from 17L1. This finding prepares the way for the cloning of NF1.

JAK2 V617F is a rare finding in de novo acute myeloid leukemia, but STAT3 activation is common and remains unexplained.

Signal transducer and activator of transcription (STAT) proteins are phosphorylated and activated by Janus kinases (JAKs). Recently, several groups identified a recurrent somatic point mutation constitutively activating the hematopoietic growth factor receptor-associated JAK2 tyrosine kinase in diverse chronic myeloid disorders - most commonly classic myeloproliferative disorders (MPD), especially polycythemia vera. We hypothesized that the JAK2 V617F mutation might also be present in samples from patients with acute myeloid leukemia (AML), especially erythroleukemia (AML-M6) or megakaryoblastic leukemia (AML-M7), where it might mimic erythropoietin or thrombopoietin signaling. First, we documented STAT3 activation by immunoblotting in AML-M6 and other AML subtypes. Immunoperoxidase staining confirmed phosphorylated STAT3 in malignant myeloblasts (21% of cases, including all AML-M3 samples tested). We then analyzed genomic DNA from 162 AML, 30 B-cell lymphoma, and 10 chronic lymphocytic leukemia (CLL) samples for JAK2 mutations, and assayed a subset for SOCS1 and FLT3 mutations. Janus kinase2 V617F was present in 13/162 AML samples (8%): 10/13 transformed MPD, and three apparent de novo AML (one of 12 AML-M6, one of 24 AML-M7, and one AML-M2 - all mixed clonality). FLT3 mutations were present in 5/32 (16%), while SOCS1 mutations were totally absent. Lymphoproliferative disorder samples were both JAK2 and SOCS1 wild type. Thus, while JAK2 V617F is uncommon in de novo AML and probably does not occur in lymphoid malignancy, unexplained STAT3 activation is common in AML. Janus kinase2 extrinsic regulators and other proteins in the JAK-STAT pathway should be interrogated to explain frequent STAT activation in AML.

FIP1L1-PDGFRA in eosinophilic disorders: prevalence in routine clinical practice, long-term experience with imatinib therapy, and a critical review of the literature.

We previously studied clinico-pathologic features of 89 consecutive adult patients with moderate-to-severe eosinophilia, and reported a FIP1L1-PDGFRA prevalence of 12%. In that series, all 11 FIP1L1-PDGFRA+ patients receiving imatinib achieved a complete response. We now extend our observations through a study of 741 unselected patients with eosinophilia for FIP1L1-PDGFRA, and present longer term follow up data for the imatinib-treated cohort. We also include data for three previously unreported FIP1L1-PDGFRA+ patients. Among the 741 requests, only 21 (3%) were found to carry the FIP1L1-PDGFRA mutation. While all 14 FIP1L1-PDGFRA+ patients receiving imatinib achieved a complete response, the 4 patients who attempted to discontinue imatinib all relapsed. We also find that it is possible to maintain patients in clinical remission with an empirically derived schedule of low-dose (50-100 mg), intermittent (once daily to once weekly) imatinib. Lastly, we present a comprehensive review of the literature pertaining to FIP1L1-PDGFRA in order to address several key aspects of this mutation from a clinical standpoint.

Chronic neutrophilic leukemia (CNL): a clinical, pathologic and cytogenetic study.

This report describes a single institution's recent experience with six patients fulfilling the diagnostic criteria of chronic neutrophilic leukemia. No patient had the Philadelphia chromosome or the BCR/ABL fusion gene. None of the common cytogenetic abnormalities characteristic of myeloid disorders were detected. Two patients demonstrated clonal evolution during the course of the disease. All responded initially to therapy with hydroxyurea with control of leukocytosis and reduction in splenomegaly. Three patients eventually became refractory to hydroxyurea, manifesting progressive neutrophilia without blastic transformation. Aggressive chemotherapy to control progressive leukocytosis resulted in death due to cytopenias in two of these patients. The third patient received less intensive chemotherapy and died of progressive disease. One patient died after transformation of the disease into undifferentiated acute myeloid leukemia. Two patients remain alive with stable disease on hydroxyurea therapy, 12 and 54 months after initial diagnosis. Chronic neutrophilic leukemia is a rare clinicopathologic entity that can be distinguished from chronic myelogenous leukemia, the recently described neutrophilic-chronic myelogenous leukemia, and myelodysplastic syndrome. The clinical course is heterogeneous, with a definite risk of death from either blastic transformation or progressive neutrophilic leukocytosis. Continued study and reporting of these cases must be encouraged.

Primary pulmonary MALT lymphomas show frequent and heterogeneous cytogenetic abnormalities, including aneuploidy and translocations involving API2 and MALT1 and IGH and MALT1.

API2-MALT1 fusion and aneuploidy are common chromosomal abnormalities in MALT lymphoma. In studying their incidence and relationship in primary pulmonary MALT lymphomas, a translocation involving MALT1 and IGH was also identified. In all, 28 primary pulmonary MALT lymphomas were studied by fluorescence in situ hybridization using an API2-MALT1 probe and multiple centromeric probes, as well as IGH-BCL2, IGH-MALT1, and MALT1 breakapart probes in selected cases. Seven (25%) had API2-MALT1 fusion; all seven lacked aneuploidy except for two with trisomy 3 in a small clone. Three (11%) had IGH-MALT1 fusion; two also showed trisomy 3 and 12. A total of 11 (39%) had aneuploidy only, with trisomy 3 and 18 being the most common. Ectopic nuclear bcl-10 expression, which has been previously associated with API2-MALT1, was seen by immunohistochemistry in 86% of API2-MALT1 fusion-positive cases, one IGH-MALT1 fusion-positive case, two aneuploidy-only cases, and two normal cases. In primary pulmonary MALT lymphomas, cytogenetic abnormalities are common (75%) and heterogeneous, encompassing API2-MALT1 and IGH-MALT1, which are mutually exclusive, as well as aneuploidy, which may be present in the latter but is rare in the former. Ectopic nuclear bcl-10 expression is associated with API2-MALT1 but may also be seen in IGH-MALT1 fusion-positive, aneuploidy-only, and normal cases.

B-CLL cells are capable of synthesis and secretion of both pro- and anti-angiogenic molecules.

Initial work has shown that clonal B cells from B-chronic lymphocytic leukemia (B-CLL) are able to synthesize pro-angiogenic molecules. In this study, our goal was to study the spectrum of angiogenic factors and receptors expressed in the CLL B cell. We used ELISA assays to determine the levels of basic fibroblast growth factors (bFGF), vascular endothelial growth factor (VEGF), endostatin, interferon-alpha (IFN-alpha) and thrombospondin-1 (TSP-1) secreted into culture medium by purified CLL B cells. These data demonstrated that CLL B cells spontaneously secrete a variety of pro- and anti-angiogenic factors, including bFGF (23.9 pg/ml +/- 7.9; mean +/- s.e.m.), VEGF (12.5 pg/ml +/- 2.3) and TSP-1 (1.9 ng/ml +/- 0.3). Out of these three factors, CLL B cells consistently secreted bFGF and TSP-1, while VEGF was expressed in approximately two-thirds of CLL patients. Of interest, hypoxic conditions dramatically upregulated VEGF expression at both the mRNA and protein levels. We also employed ribonuclease protection assays to assay CLL B cell expression of a variety of other angiogenesis-related molecules. These analyses revealed that CLL B cells consistently express mRNA for VEGF receptor 1 (VEGFR1), thrombin receptor, endoglin, and angiopoietin. Further analysis of VEGFR expression by RT-PCR revealed that CLL B cells expressed both VEGFR1 mRNA and VEGFR2 mRNA. In summary, these data collectively indicate that CLL B cells express both pro- and anti-angiogenic molecules and several vascular factor receptors. Because of the co-expression of angiogenic molecules and receptors for some of these molecules, these data suggest that the biology of the leukemic cells may also be directly impacted by angiogenic factors as a result of autocrine pathways of stimulation.

Deletions of chromosome 13 in multiple myeloma identified by interphase FISH usually denote large deletions of the q arm or monosomy.

Deletions of the long arm of chromosome 13 (13q-) are observed in patients with multiple myeloma (MM), are rarely observed in the monoclonal gammopathy of undetermined significance (MGUS) and have been associated with a worsened prognosis in MM. However, no minimally deleted region in the 13q arm has been defined at 13q, and consequently no tumor suppressor genes have yet been identified that are important for disease pathogenesis. We attempted to characterize these chromosome 13q deletions at the molecular cytogenetic level. We studied 351 newly diagnosed patients, entered into the E9486/E9487 clinical study of the Eastern Cooperative Oncology Group. Fluorescent in situ hybridization (FISH) combined with immune fluorescent detection (cIg-FISH) of clonal plasma cells (PC) and cytomorphology were used to analyze interphase, bone marrow (BM) cell, cytospin slides. We simultaneously used DNA probes for the following locus specific probes (LSI); LSI 13 (Rb) and D13S319, which hybridize to 13q14. We subsequently studied distal deletions using the D13S25 probe (13q14.3) and a subtelomeric probe (13qSTP) for the 13q-arm (D13S327) in 40 cases with documented LSI 13 (Rb)/D13S319 deletion and 40 without deletion of these loci. Of 325 evaluable patients, we found 13q deletions in 176 (54%) using LSI 13 (Rb) and D13S319 probes. Of 40 patients with LSI 13 (Rb)/D13S319 deletions, 34 (85%) had coexistent deletion of both D13S25/13qSTP. These results indicate that chromosome 13 deletions in MM involve loss of most if not all of the 13q arm perhaps even indicating monosomy. In six cases the 13qSTP signal was conserved, but D13S25 was lost indicating large interstitial deletions involving 13q14. In 39 of the 40 cases without LSI 13 (Rb)/D13S319 deletions, the normal pattern of two pairs of signals was observed for D13S25/13qSTP. Deletions involving 13q14 are very common in MM as detected by cIg-FISH. These deletions appear to predominantly involve loss of large segments of the 13q arm or monosomy 13, and only occasionally represent an interstitial deletion.

Chromosome abnormalities clustering and its implications for pathogenesis and prognosis in myeloma.

The nonrandom recurrent nature of chromosome abnormalities in myeloma suggests a role for them in disease pathogenesis. We performed a careful cytogenetic analysis of patients with abnormal karyotypes (n = 254), to discern patterns of association, search for novel abnormalities and elucidate clinical implications. Patients with karyotypic abnormalities suggestive of myelodysplasia/acute leukemia were excluded. In this study we compared survival by abnormality only between patients with abnormal karyotypes. Patients with abnormalities were more likely to have features of aggressive disease as compared to all other patients without abnormalities entered into the myeloma database (lower hemoglobin, higher beta(2)-microglobulin, labeling-index and plasmocytosis; all P < 0.0001). Several groups of patients could be readily identified; hypodiploid (22%), pseudodiploid (36%), hyperdiploid (31%) and near-tetraploid (11%). Clustering associations were seen among several trisomies and monosomy of chromosome 13 and 14. Several monosomies (-2, -3, -13, -14 and -19), 1p translocations/ deletions, and hypodiploidy were associated with a significantly shorter survival. Trisomy of chromosome 13 was rare ( <2%). Even among patients with abnormal karyotypes, specific chromosome abnormalities can impart biologic variability in myeloma, including several monosomies, hypodiploidy and abnormalities of 1p.

Karyotypic analysis in primary myelodysplastic syndromes.

Cytogenetics has provided new insights into the biology and pathogenesis of myelodysplastic syndromes. In patients with refractory anemia, it has provided proof of clonality and has helped differentiate chronic myelomonocytic leukemia from chronic myeloid leukemia. As a prognostic tool, cytogenetics has been predictive of duration of survival and leukemic transformation. However, its role as an independent prognostic factor compared with recent prognostic scoring systems remains to be determined. New techniques such as fluorescent in situ hybridization using chromosome-specific DNA probes may expand the usefulness of cytogenetics. The prognostic impact of cytogenetics may not be fully realized until more effective treatments become available.

Hereditary neuropathy with liability to pressure palsies and inherited brachial plexus neuropathy--two genetically distinct disorders.

OBJECTIVE: To determine whether hereditary neuropathy with liability to pressure palsies (HNPP) and inherited brachial plexus neuropathy (IBPN) are genetically distinct disorders and to evaluate the usefulness of fluorescence in situ hybridization (FISH) for diagnosing HNPP in individual patients. DESIGN: We studied representative metaphases from patients with HNPP and IBPN with use of FISH and a DNA probe. MATERIAL AND METHODS: With use of FISH, 14 persons from 4 unrelated families with HNPP and 7 members from 3 unrelated families with IBPN were studied. We used a DNA probe that hybridizes to chromosome 17p11.2 in an area thought to be deleted in HNPP. RESULTS: Each participant in this study who had HNPP showed deletion of this chromosome site. Each of the 10 control subjects and 7 patients with IBPN showed normal fluorescent signals on both number 17 chromosomes. CONCLUSION: These results demonstrate that HNPP and IBPN are genetically different. FISH with this probe is a sensitive and specific method for detecting the chromosomal deletion in individual patients without the use of family studies or linkage analysis.

Cytogenetic diagnosis of malignant pleural effusions: culture methods to supplement direct preparations in diagnosis.

Pleural effusions from 100 unselected patients were studied cytogenetically by direct preparation, 24- and 48-hour cultures, and long-term cultures. The study included benign pleural effusion in 17 patients, malignant pleural effusion in 76, and an indeterminate cause in 7. Two cytogenetic criteria for detecting a malignant lesion were tested: (1) three or more metaphases that were either hyperdiploid or had markers and (2) two or more metaphases with the same markers (clone). Among the malignant pleural effusions, 51 (67%) were positive by at least one method when the first criterion was used and 34 (45%) were positive by at least one method when the second criterion was used. By the first criterion, at least one of the culture methods was positive in 13 cases (17%) in which direct preparations were negative; there was 7 such cases (9%) by the second criterion. Apparently, culture methods alone are not better than direct preparations but are useful in supplementing direct preparations. There was one false-positive long-term culture by the first criterion. Thus, the clone criterion of malignancy may be more accurate but is less sensitive. There was no evidence that therapy had any effect on the cytogenetic studies.

Detection of hyperdiploid malignant cells in pleural effusions with chromosome-specific probes and fluorescence in situ hybridization.

OBJECTIVE: To compare the efficacy of fluorescence in situ hybridization (FISH) by using chromosome-specific probes with standard cytology and cytogenetics for detection of hyperdiploid malignant cells in pleural effusions. MATERIAL AND METHODS: A blind study was done on 26 pleural effusions from 25 patients who had undergone thoracentesis (14 with and 11 without a malignant condition). Cytology, cytogenetics, and FISH with probes specific for chromosomes 7, 8, 12, 18, X, and Y were done on each pleural effusion. For FISH studies, malignant specimens were defined as having 8% or more of cells with hyperdiploidy. RESULTS: Results of cytology and FISH were both normal in each of the 11 patients with benign pleural effusions. Cytogenetic studies were successful in six of these patients: five were chromosomally normal, but one male patient had an abnormal clone that lacked a Y chromosome. Among the 14 patients with malignant pleural effusions, cytology and FISH were abnormal in 8 and 6, respectively. Cytogenetic studies were successful in 11 of these patients, and an abnormal clone was found in 5. CONCLUSION: FISH can detect hyperdiploid malignant cells in pleural effusions and can be useful in the work-up of patients suspected of having malignant pleural effusions.

Chronic granulocytic leukemia: recent information on pathogenesis, diagnosis, and disease monitoring.

Current evidence strongly implicates the chromosome translocation t(9;22)(q34;q11.2) as the cause of chronic granulocytic leukemia. Therefore, identification of this genetic abnormality through either cytogenetic or molecular methods has become a requirement for diagnosis. Intense investigation of the mechanism by which t(9;22) transforms normal hematopoietic progenitors into malignant cells is ongoing. Recent advances in molecular diagnostic methods have allowed refined qualitative and quantitative methods of detecting t(9;22), which are useful for monitoring response status and detecting minimal residual disease. The current understanding of the pathogenesis of chronic granulocytic leukemia and the application of new diagnostic methods are discussed.

Cytogenetic studies in 174 consecutive patients with preleukemic or myelodysplastic syndromes.

Routine cytogenetic studies were done in 174 consecutive patients with preleukemic or myelodysplastic syndromes (PL/MDS): 5 had the 5q - syndrome, 2 had refractory cytopenia, 43 had refractory anemia, 38 had refractory anemia with ringed sideroblasts, 69 had refractory anemia with excess blasts, 6 had refractory anemia with excess blasts in transition, and 11 had chronic myelomonocytic leukemia. Successful chromosome studies were accomplished in 167 patients (96%); 64 (37%) had a chromosomally abnormal clone. Abnormal clones were most common among patients who had refractory anemia with excess blasts (45%), refractory anemia with excess blasts in transition (60%), and chronic myelomonocytic leukemia (45%); they were least common among patients with refractory anemia (32%) and refractory anemia with ringed sideroblasts (21%). The two patients with refractory cytopenia had normal cytogenetic results. Each patient with the 5q - syndrome had a 5q-chromosome, as this is a prerequisite for the diagnosis. The two most common structural abnormalities were deletion of part of a chromosome 5 long arm (17 patients) and deletion of part of a chromosome 20 long arm (8 patients). Nonspecific structural abnormalities of chromosomes 1, 3, 6, and 17 were also common. The most common numeric abnormalities were monosomy 5 (7 patients), monosomy 7 (4 patients), loss of the Y chromosome (9 patients), and trisomy 8 (20 patients). No chromosome abnormalities were specifically associated with any PL/MDS classification.

Chromosome abnormalities in malignant hematologic disorders.

Certain chromosome abnormalities have been detected in routine cytogenetic studies of patients with hematologic disorders. This article is a cytogenetic and clinical review of 28 structural and 15 numeric chromosome abnormalities. As a group, the structural abnormalities involved 40 different chromosome breakpoints and included 13 types of translocations, 8 deletions, 3 isochromosomes, 3 inversions, and 1 duplication. The numeric abnormalities included 4 types of monosomy, 10 trisomies, and a near-haploid category. We determined the relative frequency for each of these anomalies in our practice by reviewing the results of 1,228 consecutive specimens studied between 1979 and 1984 in which a chromosomally abnormal clone was found; 61% of these specimens had one or more of the selected anomalies. The three most common translocations were 9;22 translocations (378 specimens), 8;21 translocations (15 specimens), and unbalanced abnormalities derived from 1;7 translocations (13 specimens). The two most common deletions were those involving the long arm of chromosomes 5 (101 specimens) and 20 (65 specimens). The most common isochromosome was i(17q) (33 specimens). The two most common types of monosomy were loss of a Y chromosome (118 specimens) and monosomy 7 (97 specimens). The three most common trisomies were + 8 (161 specimens), +21 (53 specimens), and +19 (31 specimens). Each of the 43 anomalies was observed in patients with different types of hematologic disorders, but in most cases one kind of neoplasm usually predominated.

Chromosome studies in 104 patients with polycythemia vera.

Chromosome studies were done in 104 patients with various stages of polycythemia vera (PV): 10 had leukemia-myelodysplastic syndrome, 28 had post-PV with myeloid metaplasia (PPVMM), 12 had PV with myelofibrosis, and 54 had PV. Chromosome studies were successful in 86 patients, 37 (43%) of whom had a chromosome abnormality. At diagnosis, 4 of 28 patients (14%) had an abnormal clone; the incidence was 78% in PPVMM and 100% in leukemia-myelodysplastic syndrome. Among the 63 patients with successful chromosome studies during the first 10 years of disease, 27% had an abnormal clone. In contrast, of the 23 patients who had the disease for more than 10 years, 87% had an abnormal clone. Chromosome abnormalities were found in 11 of the 60 patients who either were untreated or underwent only phlebotomy and in 26 of the 44 patients who were treated with myelosuppressive agents. Trisomy 8, +9, and 20q- were found in some patients early during the course of their disease and also among untreated patients. These chromosome abnormalities seem to be related to the natural course of PV rather than to therapy. Patients with a chromosomally abnormal clone at the time of diagnosis of PV had a poorer survival than did those with only normal metaphases. Cytogenetic results did not predict evolution of the disease, but they did provide clues to hematologic phenotype, duration of the disease, and consequences of myelosuppressive therapy.

Chromosomally abnormal clones and nonrandom telomeric translocations in cardiac myxomas.

Cardiac myxomas from eight patients were examined cytogenetically in short-term cultures. Cultures could not be established in two of the eight cases. Chromosomally abnormal clones occurred in two of the myxomas; their karyotypes were 45,X,-Y,+7,-18 and 45,X,-Y. In three other myxomas, we found a rare kind of telomere-to-telomere translocation between chromosomes. The telomeres predominantly involved in these three tumors were the 2qter (the end of the long arm of chromosome 2), the 12pter (the end of the short arm of chromosome 12), and Yqter (the end of the long arm of the Y chromosome), respectively. In one other myxoma, 20% of the cells were tetraploid. These findings support the concept that myxomas are neoplastic; those with an abnormal clone may even have malignant potential. The unusual telomere-to-telomere translocations were not observed in a clonal pattern. They may represent a specific type of chromosomal instability associated with a defect in repair or replication of telomeric DNA.

Efficacy of fluorescence in situ hybridization for detecting PML/RARA gene fusion in treated and untreated acute promyelocytic leukemia.

OBJECTIVE: To test the efficacy of fluorescence in situ hybridization (FISH) for detection of fusion of the promyelocytic leukemia (PML) and retinoic acid receptor alpha (RARA) genes in patients with treated or untreated acute promyelocytic leukemia (APL). DESIGN: We conducted a retrospective blind study on a series of stored bone marrow specimens from normal subjects and patients with APL. MATERIAL AND METHODS: Conventional cytogenetic and FISH analyses were done on interphase and metaphase cells in specimens from 31 normal subjects and 19 patients with untreated or treated APL. RESULTS: From 25 of the normal specimens, we calculated a normal cutoff of 10% for interphase cells and 0% for metaphase cells. With use of these criteria, the other six specimens from normal subjects showed normal findings, and each of the seven specimens from patients with untreated APL was abnormal by FISH analysis. The specimens from four patients in clinical relapse or with residual APL were abnormal. Of the eight specimens from patients in clinical remission, three were abnormal; two of these patients had a relapse within 8 months, and the other patient had received 1 month of chemotherapy and was entering remission. Of the other five patients in remission, four had normal FISH results and have now been in remission for 2.5 to 10 years. The other patient in remission with normal FISH results had a relapse within 6 months. PML/RARA fusion was detectable in three patients with hypogranular APL and in three with a cytogenetic variant of the t(15;17). CONCLUSION: The results of this study suggest that FISH with PML and RARA probes can be used to diagnose APL and may be useful for monitoring treated patients.

Erythrophagocytic acute lymphocytic leukemia with B-cell markers and with a 20q- chromosome abnormality.

An erythrophagocytic neoplastic infiltration of the bone marrow which resembled malignant histiocytosis was found in an elderly man who, when initially examined, had fever and cytopenias. Results of cytochemical and immunologic studies were consistent with an acute lymphocytic leukemia in which the lymphoblasts showed the simultaneous expression of lymphoid stem cell and B-cell markers. Chromosome analysis revealed an abnormal clone with a deletion of part of the long arm of chromosome 20. This case illustrates (1) the occurrence of striking erythrophagocytosis by lymphoblasts at the time of initial presentation of a patient with acute lymphocytic leukemia, (2) the fact that abnormalities of chromosome 20 can occur in patients with acute lymphocytic leukemia, and (3) the capability of lymphoid malignant lesions to show the simultaneous expression of antigens that are characteristic of different stages of lymphoid differentiation.

Prenatal detection of aneuploidy by directly labeled multicolored probes and interphase fluorescence in situ hybridization.

OBJECTIVE: To detect aneuploidy of chromosomes 13, 18, 21, X, and Y with use of new, directly labeled, multicolored, commercially available DNA probes from interphase cells of amniotic fluid (AF). MATERIAL AND METHODS: The hybridization sites of the five probes were validated by metaphase analysis. The fluorescence in situ hybridization (FISH) normal range was determined from a series of normal AF specimens and tested on a series of normal and abnormal specimens. RESULTS: The hybridization efficiencies of the five probes were 100%. The mean AF interphase disomic signal patterns for chromosomes 13, 18, 21, XX, and XY were 95.9%, 89.1%, 94.3%, 94.7%, and 98.7%, respectively. Of a total of 508 cases analyzed, 211 were aneuploid. All cases were correctly identified and no false results occurred (in comparison with karyotypic analysis), although maternal cell contamination was relatively common. CONCLUSION: Clinical screening for aneuploidy of chromosomes 13, 18, 21, X, and Y from interphase AF cells is possible with use of these probes and FISH. Cases of maternal cell contamination and mosaicism necessitate cautious interpretation. The FISH procedure is recommended for screening of common aneuploidies, followed by a complete chromosome analysis to detect anomalies.