HLA phenotype alteration is associated with DNA ploidy of the cells within one tumor. Flow cytometry analysis of case 55 reveals a synchronous divergence of tumor cell populations with DNA ploidy and HLA expression. Keratin positive (ker+, black) epithelial cells are distinguished from vimentin positive (vim+, light gray) stroma cells and infiltrating leukocytes (a). Compared to the diploid vim+ cells (b), peri-diploid and aneuploid cell populations of ker+ cells are revealed (c). By plotting HLA expression to DNA content, 3 ker+ cell populations can be discriminated, including a HLA negative DNA diploid tumor cell population and a HLA positive aneuploid population (d).