Interphase Cytogenetics of Chromosomes 11 and 17 in Fine Needle Aspirates of Breast Cancer DAMIAN T. McMANUS, BSc, MD, MRCPATH, ANNA H. PATTERSON,MSc, PERRY MAXWELL, PHD, PETERW. HAMILTON, PHD, NElL H. ANDERSON, BSc, MD, MRCPATH, LINDA M. CAUGHLEY, MB FRCPATH,AND PETER G. TONER, DSc, FRCP, FRCPATH The aims of this investigation were to compare quantitative with qualitative analysis of fluorescent in situ hybridization (FISH) centro- mere signals in interphase breast cancer cell nuclei and to evaluate the possible clinical utility of detecting numerical abnormalities of chromosomes 11 and 17 by FISH in the preoperative prediction of breast cancer histological grade. Commercial digoxigenin-labeled centromere probes to chromosomes 11 and 17 were hybridized to 69 malignant aspirates with histological follow-up. Aspirates were catego- rized as disomic or aneusomic for chromosomes 11 and 17 qualita- tively; a subset of aspirates was also analyzed quantitatively. The quantitative and qualitative approaches resulted in almost identical categorisation. There was a significant association between the qualita- tive categorization of aspirates as aneusomic or disomic, the histologi- cal grade of the excised tumours (P = .0695, n = 69), and the cytological grade of the clinical aspirates (P = .006, n = 35). al- though histological grade III tumors were almost invariably polysomic for one or both chromosomes, polysomy was also detected in grade I and II tumors. Qualitative FISH analysis was shown to be more sensitive than cytological grading in predicting histological grade III but was of lower specificity and was therefore not clinically useful. HUM PATHOL 30:137-144. Copyright © 1999 by W.B. Saunders Com- pany Key words: breast cancer, fine needle aspirates, interphase cytoge- netics, chromosomes 11 and 17, tumor grading. Abbreviations: FISH, fluorescent in situ hybridization; FNA, fine- needle aspiration; SSC, saline sodium citrate. Interphase cytogenetics may be defined as the direct detection of specific DNA sequences within the intact interphase nucleus for the purpose of karyotypic analysisX; such abnormalities are often detected using fluorescence in situ hybridization (FISH).2 Probes di- rected against unique sequences can be used to detect translocations ~,4 or gene amplification 5 and deletion. 6 The use of probes directed against pericentromeric alphoid repeat sequences allows the detection of numeri- cal chromosomal abnormalities (aneuploidy) in inter- phase nuclei. 7-9 Breast cancer fine-needle aspirates are in many respects ideal specimens for interphase cytogenetic studies, because aspirates contain a population of un- fixed tumor cells with intact nuclei that are usually representative of the tumor. Numerical chromosome a b n o r m a l i t i e s 1°-13 a n d erbB2 oncogene amplification 14 have been detected in breast cancer aspirates by such techniques. It has been suggested that the detection of aneu- From the Immunocytochemistry and Molecular Pathology Labo- ratory, Tissue Pathology, The Belfast Link Laboratories, and The Queen's University of Belfast, Northern Ireland, United Kingdom. Accepted for publication July 16, 1998. Presented in part as an oral presentation at the British Society of Clinical Cytology, Liverpool 1996. This work was funded by project grants to DT McManus from DHSS, Northern Ireland, and a local charity, Action Cancer. Address correspondence and reprint requests to D.T. Me Manus, BSc, MD, MRCPath, Department of Pathology, Queen's University of Belt:ast, Royal Group of Hospitals Trust, Belfast BT12 6BA Northern Ireland. Copyright © 1999 by W.B. Saunders Company 0046-8177/99/3002-0005510.00/0 ploidy by FISH might be usefifl in the differential diagnosis of malignant aspirates, is but aneuploidy also has been shown in proliferative breast diseasea5and atypical hyperpla- sia. 16 In contrast, lobular carcinoma, frequently difficult to diagnose by fine-needle aspiration (FNA), is often disomic, as are mucinous tumors. 17 These findings could limit the usefulness of FISH detection of aneu- ploidy as an aid to the preoperative diagnosis of malig- nancy, although FISH detection of chromosomal aneu- somy may yet find a role in the risk assessment of proliferative breast lesions. 2 The current investigation focuses instead on the potential role of FISH in the preoperative prediction of breast cancer aggressiveness. FNA cytology has a well-established role in the preoperative diagnosis of breast cancer as part of the triple approach. Recently, there has been increasing interest in the development of techniques to permit the preoperative prediction of tumor aggressiveness. Cyto- logical grading systems have been developed that show correlations between the cytological grade of the tumor cells in the aspirate and the histological grade of the excised tumors. 18,19 Although the preoperative predic- tion of tumor characteristics is not of direct clinical importance, this situation could be changed by the adoption of neo-adjuvant chemotherapy. A combina- tion of mammography, FNA cytology and core biopsy could be used to diagnose invasive malignancy and to predict tumor characteristics preoperatively. 2° Although S-phase fraction is generally regarded as the most important prognostic indicator available from flow cytometry, aneuploid DNA content correlates with histological grade and also has emerged as a possible independent predictor of prognosis in some investiga- 137