What type of malignancies are classified by grade and cell type instead of stage?

Brain and spinal cord tumors are classified by grade and cell type instead of stage because staging systems primarily used for other tumors, like solid tumors, do not apply as effectively to the central nervous system (CNS). In the context of brain and spinal cord tumors, grade refers to how abnormal the tumor cells look under a microscope, indicating how quickly the tumor is likely to grow and spread. Cell type relates to the specific kind of cells that the tumor originates from, such as neurons or glial cells.

These tumors are unique because they often present with different biological behaviors compared to other malignancies. This classification approach helps medical professionals understand the tumor’s potential aggressiveness and guides treatment decisions. Additionally, because the CNS is surrounded by protective barriers and has distinct anatomical considerations, the standard staging methods like the TNM (tumor, node, metastasis) system are not always suitable for these types of malignancies. Consequently, the focus shifts toward grade and histology in their classification.