The Concept of Malignancy: Anaplasia, Cell Proliferation, Metastasis

Abstract

In intracranial tumors the concept of malignancy has a clinical and a biological sense. Contrary to tumors in other organs, intracranial tumors grow within a closed space whose only reserve depends upon shifts in the CSF. The brain and the spinal cord are formed by different structures composed of cells in various stages of differentiation: They are, therefore, inhomogeneous from an anatomical and functional point of view. Whilst some cerebral structures may withstand severe damage for a long time without the life of the patient being compromised, others cannot tolerate, even for a short time, minimal damage. A tumor, therefore, may be “malignant” and lead to a fatal outcome solely on the basis of its location. Given the same histological appearance, an astrocytoma of the aqueduct will be more “malignant” than a similar astrocytoma in the hemisphere. The criteria of operability also play a role, so that an astrocytoma of the third ventricle may be more “malignant” than an analogous tumor of the cerebellar hemisphere.