Sample preparation from paraffin-embedded tissue specimens for laser scanning cytometric DNA analysis

We have developed a simple, rapid method for isolating cells from a block of formalin-fixed, paraffin-embedded tissue specimen for laser scanning cytometric (LSC) DNA analysis by using a grater. The scraping-like tissue samples were obtained by grating a paraffin-embedded tissue block. The grated samples were collected, put into a small plastic tube, and deparaffinized with xylene. Subsequently, the samples were immersed in 100% ethanol to remove the xylene. After using a syringe with a 26-gauge needle and filtering through 40-microm nylon mesh, the cells suspended in ethanol were dropped directly onto a glass slide. As a result, isolated cells adhered tightly to the glass slide. The slides mounted with isolated cells were treated with 0.1% pepsin in 0.1 N HCl for 1 h at 37 degrees C and then 0.1% RNase for 10 min at room temperature. The slides were dipped in propidium iodide (25 microg/ml) to stain DNA and sealed with nail varnish. The coefficients of variation for histograms were small enough to detect an aneuploid peak close to the diploid peak.