Malignant astrocytomas classification

Histology/Classification
Astrocytomas are classified by the WHO into three major grades of increasing pathologic anaplasia and rapidity of clinical progression. These are:


 * 1) Grade II (Astrocytoma)
 * 2) Grade III (anaplastic astrocytoma)
 * 3) Grade IV (glioblastoma multiforme)

Astrocytomas are the most common and can be further classified into fibrillary, gemistocytic and protoplasmic based on histology. The rarer pilocytic type of astrocytoma (Grade I) occurs in younger patients and occurs more commonly in the cerebellum. This subtype generally has a benign biologic behavior.

>90% of the time theses are solitary lesions. A characteristic of gliomas is that they tend to become more anaplastic with time. This is a heterogeneous phenomenon and different areas of the same neoplasm may have differing histologic appearances.

A pattern of genetic alterations has also been noted. Low-grade astrocytomas are associated with deletion of material on Chromosomes 6 and 13. Progression to Grade III is associated with changes on Chromosome 19q and the retinoblastoma tumor suppressor gene. Finally, progression to glioblastoma multiforme (GBM) is associated with amplification of epidermal and hepatocyte growth factor receptor and alterations of Chromosome 10q and 18q.