Interphase fluorescence in situ hybridization improves the detection of malignant cells in effusions from breast cancer patients

Flow cytometry, molecular analysis, and other special techniques (in Serous Fluid Cytopathology)

Morphological and architectural pattern evaluations play a major role in the rpretation of hematopoietic neoplasms. However, confirmation of diagnosis, classification, prognosis, and risk stratification are highly dependent on the utilization of multiple ancillary studies. The importance of these ancillary studies increases in evaluating serous fluid samples, as these samples lack architecture and patterns. Likewise, the morphology can be disturbed by sample preparation. The most common ancillary studies utilized are flow cytometry, immunohistochemistry for immunophenotyping, Fluorescent In Situ Hybridization (FISH), cytogenetics for structural and gene rearrangements, and molecular studies for mutational analysis. Among them, flow cytometry analysis is the handiest test to perform with high diagnostic yield on serous fluid specimens. In this article we will discuss the use, caveat, and role of the most common ancillary studies on serous fluid specimen evaluation. This review article will be incorporated finally as one of the chapters in CMAS (CytoJournal Monograph/Atlas Series) #2. It is modified slightly from the chapter by the initial authors (Choladda Vejabhuti, MD and Chung-Che (Jeff) Chang, MD, PhD) in the first edition of Diagnostic Cytopathology of Serous Fluids.

Heparanase expression: a potential ancillary diagnostic tool for distinguishing between malignant cells and reactive mesothelium in body cavity effusions

OBJECTIVE

Heparanase, an endoglycosidase that cleaves heparan sulphate, is frequently expressed in carcinomas and was suggested to play a role in cell invasion and metastasis. We investigated whether heparanase expression may serve as a reliable marker to discriminate benign mesothelial cells from malignant cells shed into body cavities.

METHODS AND RESULTS

Cytological smears of effusions from 51 hospitalized patients were immunostained for heparanase. Strong immunoreactivity was noted in 35 of 40 (88%) carcinoma samples and in all three malignant mesothelioma cases. Only rare (<3%) reactive mesothelial cells were noted showing a faint negligible staining. Specificity was 100%, sensitivity 88%, and positive and negative predictive values were 100% and 89% respectively.

CONCLUSIONS

Our results suggest that heparanase may be of value as a complementary component in a diagnostic panel of markers, contributing to its reliability and accuracy.

Fluorescence in situ hybridization, comparative genomic hybridization, and other molecular biology techniques in the analysis of effusions

Over the last 20 yr, the introduction of immunocytochemistry as a diagnostic tool has dramatically revolutionized diagnostic pathology. With the introduction of molecular methods as part of the diagnostic armamentarium, the practicing pathologist is facing the new challenge of grasping novel concepts of the molecular cytogenetics era. Herein, we review the diagnostic contribution of ancillary molecular techniques, including fluorescent and chromogenic in situ hybridization, telomerase assays, loss of heterozygosity, comparative genomic hybridization (CGH), and microarray-based CGH, for the practicing cytopathologists and discuss how these techniques will help pathologists in decision-making.

The utility of fluorescence in-situ hybridization in the diagnosis of malignant pleural effusion

PURPOSE OF REVIEW

Molecular tools are used to refine the diagnosis of malignancy in pleural fluids. This review discusses the rationale and recent findings of the application of one of these tools, fluorescence in-situ hybridization, in pleural effusions.

RECENT FINDINGS

Aneuploidy (i.e., pronounced numeric and structural chromosomal changes) is a recurrent finding in cells of solid tumors. Different methods attempt to detect tumor-associated aneuploidy to prove micrometastasis in different compartments, such as urine, cerebrospinal fluid, bone marrow, and body fluids. In recent years, fluorescence in-situ hybridization analysis has proved viable for detecting metastasis based on the observation of matching patterns of chromosomal aneusomies in primary tumors and corresponding metastasis.

SUMMARY

Fluorescence in-situ hybridization analysis using specific probes for visualizing numeric aberrations in a microscopic evaluation (thus complementing routine cytologic evaluation) has been shown to be relatively simple, very robust, and thus applicable in material of lesser quality and more sensitive than routine cytology. Remarkably, dual-color fluorescence in-situ hybridization analysis allows for an efficient analysis in effusions, and the approach presented in this review proved to be more specific than other molecular procedures applied in effusions to detect malignancy, such as polymerase chain reaction. Prospective studies are needed to demonstrate that refinement of staging by fluorescence in-situ hybridization or polymerase chain reaction ('molecular upstaging') will translate into meaningful therapeutic consequences.

Combination of cytology, fluorescence in situ hybridization for aneuploidy, and reverse-transcriptase polymerase chain reaction for human mammaglobin/mammaglobin B expression improves diagnosis of malignant effusions

PURPOSE

The identification of malignant cells in effusions by conventional cytology is hampered by its limited sensitivity. The aim of this study was to improve tumor cell detection in effusions by molecular approaches.

MATERIALS AND METHODS

A total of 157 effusions from patients with tumors and 72 effusions from patients without a history or evidence of malignancy were included in this study. All effusion specimens were evaluated in parallel by cytology, fluorescence in situ hybridization (FISH) for aneuploidy, and reverse-transcriptase polymerase chain reaction (RT-PCR) for expression of human mammaglobin (hMAM) and mammaglobin B (hMAM-B).

RESULTS

In effusions from patients with tumors, the sensitivities of tumor cell detection by cytology, FISH, and hMAM and hMAM-B detection were 46.2%, 53.3%, 36.4%, and 57.7%, respectively. The corresponding specificities were 94.4%, 97.0%, 87.1%, and 88.6%. Notably, a high percentage of effusions containing malignant cells were in fact transudates, indicating the necessity for molecular diagnostic work-up of transudates collected from patients with tumors. Dependent on the tumor type, the use of appropriate marker combinations improved tumor cell detection in effusions significantly. By combining all four diagnostic tests, a positive test result indicating the presence of malignancy was achieved in 81.1%, with a fairly good specificity of 70.1%.

CONCLUSION

Molecular techniques are definitely useful to detect malignancy in cytologically negative effusions. Tumor cell detection in effusions can be significantly improved by FISH and PCR techniques applying appropriate molecular markers. This finding should help to improve tumor staging, prognostic assessment, and treatment monitoring.

Malignant effusions: From diagnosis to biology

Serous effusions are a frequently encountered clinical manifestation of metastatic disease, with breast, ovarian, and lung carcinomas and malignant mesothelioma (MM) leading the list. Recently, extensive research has resulted in expansion of the antibody panel that is available for effusion diagnosis, thereby reducing the risk for error. Despite this progress, relatively little has been done in way of understanding the biology of cancer cells in effusions, especially those of nonovarian origin. The diagnosis of a malignant effusion signifies disease progression and is associated with a worse prognosis regardless of the tumor site of origin. However, survival is much more variable with ovarian cancer compared with other tumors. Furthermore, cancer cells of different origins differ considerably in their biology and have unique phenotypic and genotypic characteristics. This review summarizes the current knowledge in this field and presents a model for the study of tumor metastasis and disease progression, through large comparative studies of malignant cells in effusions, primary tumors, and solid metastases. The case also is made for potential applications of this rapidly evolving body of knowledge in the diagnosis, classification, and prediction of biological behavior of processes resulting in cryptic effusions at the clinical level.

Chromosomal abnormalities in non-small cell lung carcinomas and in bronchial epithelia of high-risk smokers detected by multi-target interphase fluorescence in situ hybridization

Human lung carcinogenesis is accompanied by complex chromosomal changes that may be detected in interphase cells by fluorescence in situ hybridization (FISH) assay using recently developed multitarget DNA probes. Touch preparations of 20 non-small cell lung carcinomas, sputum specimens from 3 patients with lung cancer and from 11 ex-smokers without lung cancer, and cultured benign bronchial epithelium of 42 high-risk smokers, 9 of whom had concurrent invasive carcinoma, were tested using a four-color FISH probe (LAVysion) targeting centromere 6, 5p15.2, 7p12 (EGFR), and 8q24 (MYC). Significantly high frequencies of abnormal cells were found in each of the 20 NSCLC (100%) and in the 3 sputum specimens from lung cancer patients. None of the cytologically normal sputa contained FISH abnormalities. Cultured bronchial epithelial cells from 11 of 42 patients (26%) were abnormal for at least one probe. Abnormal FISH patterns had no association with gender, presence of tumor or histology. Multicolor FISH can readily detect chromosomal abnormalities in imprints and sputa from lung carcinomas. Chromosomal aneusomy is also frequent in bronchial epithelial cells from long-term smokers. The prognostic significance of the multicolor LAVysion FISH probe set should be validated in a controlled clinical trial.

Patterns of aneusomy for three chromosomes in individual cells from breast cancer tumors

Multi-color fluorescence in situ hybridization (FISH) can determine the changes in the copy numbers of several chromosomes simultaneously and can therefore be used to identify aneusomic patterns in individual cells. Aneusomic patterns may be useful for determining the malignant nature of rare epithelial cells in the blood of cancer patients. Touch preparations from 74 primary breast tumors were evaluated for aneusomy of chromosomes 1, 8 and 17 by tri-color-FISH. In the first part of the analysis, percentages of aneusomy for individual chromosomes and their combinations were determined. In the second part of the analysis, aneusomic patterns for these three chromosomes were analyzed in individual tumor cells and compared to aneusomic patterns observed in leukocytes and in individual cells from benign and normal breast tissue to determine aneusomic patterns indicative of malignancy. Ninety-two percentage of the primary breast carcinomas showed aneusomy for one or more enumerator probes. Comparison with benign breast tissue identified six aneusomic patterns in individual carcinoma cells indicative for malignancy by statistical analysis and not observed in leukocytes. Hence, certain patterns of aneusomy in individual cells involving chromosomes 1, 8 and 17 are indicative of malignancy in individual breast tumor cells and may be useful for determining malignancy of rare epithelial cells in the blood of breast cancer patients.

Glucose transporter Glut-1 is of limited value for detecting breast carcinoma in serous effusions

Diagnosing breast carcinoma that has metastasized to body cavity fluids can be difficult. Recently, immunostaining for the facultative glucose transporter Glut-1 has been described as a sensitive and specific means of detecting carcinomas in effusions. However, only five cases of breast carcinoma were studied. We examined Glut-1 specifically as a means of detecting breast carcinoma in effusion cytology. Using avidin-biotin immunocytochemistry, cell block material from 31 cases of breast carcinoma metastatic to body cavity effusions and 33 cases of benign effusions were studied. All cases were immunostained with the Glut-1 antibody. An additional set of slides from these same cases was stained for mucin using the Mayer's mucicarmine technique. Slides were graded for percentage of cells exhibiting immunoreactivity for Glut-1 or for the presence of mucin. Results of staining for both Glut-1 alone and in combination with mucicarmine were compared between the benign and malignant groups. Of the breast cancer cases, 19 of 31 (61%) were immunoreactive for Glut-1, and 25 of 31 (81%) were positive for either Glut-1 or mucicarmine. One of the 33 (3%) benign cases was immunoreactive for Glut-1, and none were positive for mucin. These data suggest that using Glut-1 as a single immunostain or in conjunction with mucicarmine is a specific but modestly sensitive means of detecting breast carcinoma in this cytologic setting.

Diagnostic value of a second generation CA 15-3 antibody to detect adenocarcinoma in body cavity effusions

BACKGROUND

Detecting malignant cells in body cavity effusions can be diagnostically challenging. Several monoclonal antibodies have been studied to improve the diagnostic yield of effusion cytology but without widespread acceptance. The CA 15-3 antibody has demonstrated high sensitivity but limited specificity for breast carcinoma in surgical pathology. A second generation CA 15-3 antibody has been developed that has not been studied in serous effusions to the authors' knowledge. The authors examined this second generation CA 15-3 antibody for its diagnostic utility in detecting adenocarcinomas in this cytologic setting.

METHODS

Cell block material from 114 cases of unequivocally benign or malignant body cavity effusions were studied. Slides were stained for CA 15-3 by using the avidin-biotin complex method. The percentage of cells exhibiting strong staining was estimated both for breast carcinoma and for all adenocarcinomas as a group. These results were compared with CA 15-3 staining exhibited by benign mesothelium.

RESULTS

CA 15-3 was expressed in at least 10% of tumor cells in 97% of breast carcinoma cases and in 90% of adenocarcinomas overall. The highest sensitivity was observed in carcinomas of the breast, ovary, and lung. Of 40 cases of benign mesothelium, only 4 (10%) were positive (P < 0.001). The sensitivity of CA 15-3 was 97% for breast carcinoma and 91% for adenocarcinomas overall. Specificity was 95% for breast carcinoma and 91% for adenocarcinomas.

CONCLUSIONS

CA 15-3 is an immunostain with high specificity and sensitivity for adenocarcinomas in cell block material from effusions. The antibody holds particular promise for detecting breast carcinoma. Cancer (Cancer Cytopathol)

Aneuploidy of chromosome 7 can be detected in invasive lung cancer and associated premalignant lesions of the lung by fluorescence in situ hybridisation

In the present study the chromosomal status of seven invasive non small cell lung cancer specimens and associated premalignant lesions was investigated. By fluorescence in situ hybridisation (FISH) with centromere specific probes, an increase in the percentage of aneuploid cells from pre-invasive to invasive lesions could be demonstrated (mean 8.5 and 59%, respectively, for chromosome 7). Furthermore, mean chromosome copy numbers were higher in invasive carcinomas as compared to premalignant lesions, indicating polyploidization during tumor development. Increasing evidence suggests that aberrations of chromosome 7 occur early in the development of lung cancer. Whether these aberrations can be used as a biomarker for future neoplastic progression remains to be determined.

FHIT protein is expressed in benign mesothelium and has no clinical value in detecting carcinoma in body cavity effusions

The fragile histidine triad (FHIT) protein is a suspected tumor-suppressor gene frequently expressed in adenocarcinomas of the lung and other organs. Its expression in benign mesothelium has not been reported. This study examined the expression of FHIT in mesothelium from benign body cavity effusions. FHIT expression was also examined in a diversity of malignant effusions to evaluate any value of the FHIT protein to discriminate carcinomas from benign mesothelium. Fifty-eight cases of benign and malignant effusions were immunostained using cell block material and two different antigen retrieval methods with the ABC method. Benign and malignant cases were scored for percentage of cells with strong immunoreactivity. Benign mesothelium exhibited strong immunoreactivity for the FHIT protein in 32 of 32 (100%) cases, with 26 of 32 (81%) cases having expression in at least 50% of cells. Seventeen of 21 (81%) cases of adenocarcinomas also exhibited the FHIT protein in at least 50% of tumor cells. FHIT expression was also noted in small numbers of other malignancies. The FHIT protein is expressed consistently in benign mesothelium as well as many types of adenocarcinomas. Immunostaining for this protein has no value in discriminating adenocarcinomas from reactive mesothelium.

Malignant cell detection by fluorescence in situ hybridization (FISH) in effusions from patients with carcinoma

Cytological diagnosis of malignant cells in effusions is hampered by difficulties in the differentiation from reactive mesothelial cells. Because interphase cytogenetics by fluorescence in situ hybridization (FISH) might complement cytological evaluation, we determined the power of tumor cell detection using FISH and cytology in 201 effusions from patients with advanced cancer. Furthermore, 9 primary breast tumors were FISH-karyotyped, and chromosomal aberrations were compared with those of corresponding metastatic effusion cells. By using centromeric probes representing chromosomes 7, 8, 11, 12, 17, and 18, a rate of malignancy-associated aneusomy combined for the 6 chromosomes was detected in an overall of 44.8% of effusion specimens (range, 31.8% to 39.3% for the individual chromosome), comparable to cytology (43.3%). The combination of just 2 FISH probes (namely, representing chromosome pairs 8/11 and 8/17) was almost equally efficient in the identification of aneusomy. Approximately one fourth of the cytologically negative effusions were FISH positive and vice versa. From the initially FISH-negative effusions, 18.9% could be subsequently classified positive with dual-color FISH by visualization of intranuclear chromosomal complexity in rare aneuploid cells. Thus, "overall FISH analysis," including dual-color evaluation, identified tumor cells in significantly more effusions (55.2%, P = .001) than conventional cytology, implying greater sensitivity. Finally, our finding that numerical aberration patterns in primary breast tumors and corresponding metastatic effusions are comparable indicates that FISH examination of primary tumors will indicate the centromeric probe(s) best suited for an efficient search for metastasis in the individual case.

Molecular biology in cytopathology: current applications and future directions

The use of molecular techniques in cytopathology has become an accepted and billable practice for certain applications. Other applications still are in the developmental or experimental stages but may soon be clinically useful. The current study provides a review of these techniques including molecular detection of clonality, in situ hybridization, loss of heterozygosity, and single base mutation detection. A number of new molecular techniques recently have been described that may have a dramatic impact on diagnostic pathology. These techniques, in situ detection of single base mutations and microarray technology, are introduced and discussed in the context of potential applications to cytopathology in the future.

Sensitive fluorescent in situ hybridisation method for the characterisation of breast cancer cells in bone marrow aspirates

AIM

The presence of malignant cells in the blood and bone marrow of patients with cancer at the time of surgery may be indicative of early relapse. In addition to their numbers, the phenotypes of the micrometastatic cells might be essential in determining whether overt metastases will develop. This study aimed to establish a sensitive method for the detection and characterisation of malignant cells present in bone marrow.

METHODS

In spiking experiments, SKBR3 cells were mixed with mononuclear cells in known proportions to mimic bone marrow samples with micrometastatic cells. Tumour cells were extracted using SAM-M450 Dynabeads coupled to the MOC-31 anti-epithelial antibody, and were further analysed for amplification of erbB2 and int2 by fluorescent in situ hybridisation (FISH). erbB2 and int2 copy numbers were also determined in 15 primary breast cancers, and bone marrow samples from patients with amplification were analysed for micrometastatic cells by immunomagnetic enrichment and FISH.

RESULTS

In model experiments, cells with amplification could be detected in bead selected fractions when ratios of tumour cells (SKBR3) to mononuclear cells were as low as 10:10(7). Among the tumour samples, eight showed increased copy numbers of erbB2 and/or int2, and three of these patients had detectable numbers of tumour cells in their bone marrow: 4000, 540, and 26 tumour cells/10(7) mononuclear cells, respectively. The patient with 540 tumour cells/10(7) mononuclear cells showed high level amplification of erbB2 and suffered from a particularly aggressive disease, whereas the patient with 4000 tumour cells/10(7) mononuclear cells had favourable disease progression.

CONCLUSION

These results demonstrate the feasibility and advantage of combining immunomagnetic selection and FISH characterisation of cancer cells in bone marrow samples. It is possible that molecular characterisation of such cells could provide prognostically valuable information.

Hyperdiploidy and apparent aneusomy in mesothelial cells from non-malignant effusions as detected by fluorescence in situ hybridization (FISH)

Interphase cytogenetics by fluorescence in situ hybridization (FISH) can be used to detect malignant cells characterized by chromosomal aneuploidy. However, apparent aneusomy in normal "control" tissues has to be considered when using FISH as diagnostic tool. In effusions as model tissue exposed to metastasis, the definition of cut-off levels for background aneusomy by FISH was aimed in this study. Using centromeric probes representing chromosomes 7, 8, 11, 12, 17 and 18, extensive chromosome copy number enumeration by single-color FISH analysis was performed in pleural and ascitic effusions derived from 15 patients with various, non-malignant diseases. In all effusions, cells with gain of hybridization signals for several or all chromosomes tested were found (in up to 1.94% of cells). A consistent finding was high grade hyperdiploidy (>4 centromeric signals). Mesothelial elements mainly contributed to hyperdiploidy in effusions, as demonstrated by a combined analysis of FISH and immunocytochemistry with staining for cytokeratin. Dual-color FISH analysis showed that hyperdiploidy was predominantly corresponding to polyploidization; however, there were always minor cell populations classified as aneuploid by dual-color FISH. In conclusion, stringent criteria have to be applied to distinguish malignancy-related aneuploidy from background aneusomy by FISH.

Detection of chromosomal aberrations in tumor cells and tumor infiltrating lymphocytes by molecular cytogenetics in patients with gynecological cancer

Conventional cytogenetic studies of tumor cells from patients with breast or ovarian cancer have shown multiple chromosomal abnormalities including chromosomes 7, 12, and 17. This study was designed to analyze the cytogenetic features of tumor cells and tumor infiltrating lymphocytes (TILs) by using a combination of magnetic activated cell sorting (MACS) and fluorescence in situ hybridization (FISH). Tumor cell, peripheral blood (PB), and TIL samples from 37 patients (20 ovarian tumors, 13 breast cancers, 3 uterine sarcoma, 1 carcinoma of the filamentary tube) were analyzed for the presence of numerical aberrations of chromosomes 7, 12, and 17. All of the tumor cells showed a high frequency of numerical aberrations of chromosomes 7, 12, and 17, especially trisomies or tetrasomies. There was no statistically significant difference in the incidence of chromosomal abnormalities in tumor tissue and effusions, or between primary and relapsed disease in patients with breast or ovarian tumors. However, tumor cells from patients with solid metastatic disease had significantly higher numbers of aberrations of chromosome 7 in the primary tumor than in tumors from patients without metastases (P = 0.049), suggesting that chromosome 7 is frequently involved in the progression of disease. Monosomies and trisomies of chromosomes 7 and 12 also occurred at a low percentage of TILs without any statistically significant difference between primary and relapsed tumors. The presence of these aneuploidies might be responsible for treatment failures in the immunotherapy of gynecological cancer.

Detection of numerical chromosome 17 abnormalities in fine-needle aspirates of breast cancer using a novel in situ hybridization signal amplification method

We describe a method of in situ hybridization (ISH) to assess numerical chromosome abnormalities on alcohol-fixed smears obtained by fine-needle aspiration from breast cancer patients, using a commercially available amplification kit to demonstrate numerical chromosome alterations of chromosome 17. In this staining procedure after detection of the biotin-labeled alpha-satellite probe for chromosome 17 with avidin-biotin-peroxidase, we incorporated a signal amplification based on the peroxidase-catalyzed deposition of a biotinylated phenolic compound followed by a secondary reaction with peroxidase. The reactions are revealed by deposition of diaminobenzidine and can be analyzed in an optical microscope, with total preservation of the morphology, allowing a direct morphologic-cytogenetic correlation. A series of 25 cases of aspirates from breast cancer were analyzed with this methodology. Aneusomy was found in 14 cases (56%), whereas 11 (44%) had a normal number of chromosome 17 copies. Polysomy occurred in all aneusome cases except one. We did not find concordance between numerical chromosome abnormalities of chromosome 17 and nuclear grading as well as with the immunoexpression of p53 and c-erbB2 studied in the smears. We conclude that the application of the ISH signal amplification method on alcohol-fixed smears will eliminate the need for fresh material and will provide several advantages, such as improvement of morphological concomitant analysis without the need for a fluorescence microscope; utilization, whenever malignancy is found, without necessity to reaspirate the patient; and adequacy of archival material.

Chromosomal imbalances in primary and metastatic pancreatic carcinoma as detected by interphase cytogenetics: basic findings and clinical aspects

To date, cytogenetic studies on pancreatic carcinoma are rare, and little is known about the frequency of cytogenetic aberrations in primary carcinomas compared with metastatic tumour cells. We therefore evaluated the frequency of chromosomal aberrations in 12 primary pancreatic carcinomas and in effusion specimens from 25 patients with pancreatic cancer by using interphase fluorescence in situ hybridization (FISH) and a panel of four centromeric probes. Hyperdiploidy and chromosomal imbalances, predominantly affecting chromosome 8, were a constant finding in metastatic effusion cells, whereas concordant gain of chromosomes or relative loss of chromosome 18 characterized primary pancreatic carcinomas. The potential role of oncogenes located on chromosome 8 for pancreatic cancer progression was further investigated by double-hybridization studies of aneuploid effusion cells with a probe to 8q24 (MYC) and a centromeric probe to chromosome 8, which demonstrated amplification of the MYC oncogene in two of ten cases (20%). Finally, a potential application of basic findings in the clinical setting was tested by searching for micrometastatic cells in effusions from pancreatic cancer patients primarily negative by FISH. Two-colour FISH in combination with extensive screening (>10,000 nuclei) seems to be a useful tool to unequivocally identify micrometastatic cells by demonstrating hyperdiploidy and intranuclear chromosomal heterogeneity.

Aneuploidy of chromosome 8 as detected by interphase fluorescence in situ hybridization is a recurrent finding in primary and metastatic breast cancer

Previous work from our laboratory demonstrated aneuploidy for several chromosomes by interphase fluorescence in situ hybridization (FISH) in a high proportion of breast cancer specimens. In the literature, only limited data are available concerning chromosome 8 anomalies in breast cancer. To determine chromosome 8 ploidy status in primary and metastatic specimens from 81 breast cancer patients, FISH analysis with a DNA probe recognizing chromosome 8 centromeres was performed. In all primary tumor specimens (n = 30), significant proportions of cells were aneuploid exhibiting gain of chromosome 8 copy numbers; in 75% of effusion specimens previously classified as malignant by cytology and/or FISH for various chromosomes (n = 40), cell populations aneuploid for chromosome 8 were detected; effusions previously classified non-malignant (n = 11) were diploid in 10 cases, whereas one specimen contained rare hyperdiploid cells. Among these cells complex chromosomal aneuploidy could be demonstrated by two-color FISH, suggesting malignancy. Trisomic and tetrasomic clones were predominant in the majority of samples, but a marked intratumor cytogenetic heterogeneity was observed in most cases. Primary tumors and corresponding positive axillary lymph nodes revealed similar distributions of chromosome 8 copy numbers, analogous to previous findings with other chromosomes. This implies that, by using suitable FISH probes after examination of the respective primary tumor, an efficient search for (micro)metastasis might be feasible.