DNA index and S-phase in primary brain tumors. A comparison between fresh and deparaffinized specimens studied by flow cytometry.

Forty-nine primary intracranial tumors (33 astrocytomas, eight acoustic schwannomas, five oligodendrogliomas, and three miscellaneous tumors) were studied by flow cytometry. Each tumor specimen was divided into two portions: one was studied as an unfixed suspension stained with propidium iodide and the other after formalin fixation and paraffin embedding. The 50-microns sections from the paraffin blocks were deparaffinized, rehydrated, and enzymatically disintegrated, and the cells in suspension were stained with propidium iodide. Flow cytometry of the two portions showed a significant correlation between fresh and fixed specimens regarding the S-phase (r = 0.87) and a very close correlation fo the deoxyribonucleic acid (DNA) index (r = 0.95). When the 33 astrocytomas were analyzed separately, similar results were obtained (r = 0.86 for S-phase and r = 0.93 for DNA index, respectively). This study demonstrated a high correlation between fresh and fixed specimens for DNA ploidy and S-phase both in primary intracranial tumors in general and also in the selected subgroup of astrocytomas.