Cytogenetic Abnormalities of Primary Breast Carcinoma: Comparative Analysis of Fluorescence In Situ Hybridization (FISH) and Flow Cytometry

Abstract

: Breast cancer is a heterogeneous disease that is frequently associated with genetic alterations. Nonrandom chromosomal changes are assumed to play a role in breast tumorigenesis and progression. These changes can be detected by standard cytogenetics, which is technologically cumbersome, or by flow cytometry, which only provides a general overview of genetic alterations by ploidy status. Alternatively, fluorescence in situ hybridization (FISH) is a recently developed technique that has the capability to detect chromosomal changes in individual nuclei with preserved morphology of breast cancer. Our study was designed to investigate the molecular cytogenetic basis of nonrandom chromosomal aberrations in breast carcinoma by FISH and compare this data with flow cytometry. Large paraffin sections and 5 μm sections of 57 cases of invasive ductal carcinoma and 5 normal control samples were subjected to ploidy analysis by standard flow cytometry and FISH. By flow, 27 (47.4%) cases were aneuploid; while 30 cases were diploid. FISH, performed using a panel of six α-satellite centromeric probes for chromosomes 1, 7, 8, 11, 17, and X, detected 37 (64.9%) aneuploid tumor, while 20 tumors were diploid. Vast intratumor heterogeneity (75%) occurred in 27 of the 37 aneuploid tumors. FISH also identified aneuploidy in 50% of cases that were interpreted as diploid by flow. The FISH and flow results were concordant in 15 diploid cases and 22 aneuploid cases, yielding an overall agreement of 64.9%. This agreement was significant above that expected by chance (kappa = 0.309, p = 0.007). Sensitivity and specificity of FISH for aneuploidy detected by flow were 81.5% and 50.0%, respectively. Discordant FISH aneuploid tumors were characterized by gain or loss of 1-3 chromosomes. Normal controls were consistently diploid by both flow and FISH. Our data suggest that FISH is more sensitive in detecting aneuploidy than flow cytometry and provides valuable genetic data of breast cancer cells.