Histological observations on the regrowth of malignant gliomas after radiotherapy and chemotherapy.

The reproliferation of glioblastomas after radiation and chemotherapy has been studied in 25 tumors by means of whole mount histological preparations. The tumors have been subdivided into four groups according to the radiation dose and the distance from the end of radiation. After 4,000 rad vessel proliferations and mitoses stop, while vessel degenerations and astrocytes with deformed nuclei appear. Six months after 6,000 rad have been delivered, repopulation phenomena are clearly evident and are mainly represented by mitoses both in parenchyma and in the vessel walls, circumscribed necroses with pseudopalisadings, proliferations of formerly degenerated vessels, etc. The brain adjacent to tumor (BAT) has a great importance since it is one of the reproliferating sites, even though it may be unrecognizable for the occurrence of radiation damages.