Objective Characterization of Proliferation and Malignancy in Human Brain Tumors

Abstract

Histologic diagnosis of proliferation tendency and malignancy is — at least in certain cases — difficult and somewhat arbitrary. Objective parameters may be obtained by flow cytometric DNA measurements. The DNA content of individual cells varies during the division cycle according to a fixed schedule. Flow cytometric DNA determinations of cell suspensions yield DNA distribution patterns, DNA histograms (3, 4, 6). From a computer analysis, the fractions of cells in the various phases of the cell cycle are obtained (1, 2). This is illustrated in Figure 1. DNA content and chromosome set of the cell cycle phases G1 (prereplicative phase), S (DNA synthesis phase), and G2+M (premitotic and mitotic phase) are shown together with the corresponding idealized DNA histogram. In normal proliferative tissue, the cell populations contain a high fraction of G1 (or better nonproliferating G0) cells and a low fraction of S and (G2+M) cells. During the S phase, the DNA content is doubled, implicating that the (G2+M) cells have twice the DNA content (4C) of the G1 cells (2C). The peak position (e.g., 2C...4C) are denominated as ploidy stages. These ploidy stages permit a judgement on the malignancy of a tumor tissue.