Flow cytometric analysis of DNA ploidy and S-phase fraction in breast cancer using cells obtained by ex vivo fine-needle aspiration: an optimal method for sample collection.

: A total of 203 primary invasive breast cancers were sampled by ex vivo fine-needle aspiration (FNA), directly yielding adequate single cell suspensions for flow cytometric DNA analysis in 194 (96%). Labor-intensive and time-consuming steps of mechanical and enzymatic cellular disaggregation required by the use of fresh, frozen, or paraffin-embedded tissue were avoided, thereby minimizing preparation time. Conservation of tumor tissue allowed for the sampling of very small breast cancers. DNA ploidy and S-phase fraction data were comparable to flow cytometric data reported in other breast cancer studies using various sampling methods. Ex vivo FNA is the easiest and fastest method for sampling breast cancers for flow cytometric DNA analysis.