How Do You Grade Astrocytomas Astrocytomas

How Do You Grade Astrocytomas Astrocytomas

Astrocytomas are tumors originating from astrocytes. The WHO grading system for astrocytomas ranges from grade 1 (most benign) to grade 4 (most malignant). The grading of astrocytomas is based on analyzing tumor cells under a microscope. It is based on: How abnormal the cells look (atypia), mitosis, and vascular proliferation (Louis et al., 2021).

Grade 1 includes Pilocytic Astrocytoma, Pleomorphic Xantoastrocytoma, and Subependymal Giant Cell Astrocytoma (SEGA). Pilocytic Astrocytoma is a well-circumscribed tumor and develops slowly. It does not invade the surrounding brain, and when resected completely, it is regarded as cured and does not require chemotherapy or radiotherapy (Louis et al., 2021). Pleomorphic xanthoastrocytoma mostly originates in the temporal lobes. Its cells can have multiple shapes but do not exhibit evidence of proliferation. SEGA is common in the younger population and is usually in relation to a familiar syndrome called tuberous sclerosis (Torp et al., 2022). It typically grows inside the ventricles, which are fluid-filled spaces deep into the brain and can block the normal outflow of this fluid, causing hydrocephalus.

Grade 2 is diffuse Astrocytoma, an invasive tumor with no clear separation from the surrounding brain.

The tissue appearance moderately differs from a normal brain, but cells appear abnormal under the microscope and slightly increase in number. Grade 3 is anaplastic Astrocytoma. It is a more malignant evolution of a previously lower-grade astrocytoma, which has acquired more aggressive features, including a higher pace of growth and more invasion into the brain (Torp et al., 2022). Histologically, it exhibits higher cellular abnormalities and evidence of mitoses compared to grade 2 tumors. Grade 4 is Glioblastoma (GBM), the most malignant, aggressive, and common form of astrocytoma. It is characterized by abnormal-appearing cells, proliferation, areas of dead tissue, and the formation of new vessels.

References

Louis, D. N., Perry, A., Wesseling, P., Brat, D. J., Cree, I. A., Figarella-Branger, D., … & Ellison, D. W. (2021). The 2021 WHO classification of tumors of the central nervous system: a summary. Neuro-oncology, 23(8), 1231-1251.https://doi.org/10.1093/neuonc/noab106

Torp, S. H., Solheim, O., & Skjulsvik, A. J. (2022). The WHO 2021 Classification of Central Nervous System tumours: a practical update on what neurosurgeons need to know-a minireview. Acta neurochirurgica, 164(9), 2453–2464. https://doi.org/10.1007/s00701-022-05301-y