Astrocytomas are primary intracranial tumors derived from astrocytes of the brain. They may arise in the cerebral hemispheres, in the posterior fossa, in the optic nerve, and rarely, the spinal cord. The WHO has given a four point scale depending on the histologic grade of the tumor (see below)

The well-differentiated astrocytomas constitutes about 25 to 30% of cerebral gliomas. It has a predilection for the cerebrum, cerebellum, hypothalamus, optic nerve and chiasm, and pons. Although astrocytomas has many different histological characteristics, the most common is the well-differentiated fibrillary astrocytomas. These tumors contain the glial fibrillary acidic protein (GFAP), which is a useful diagnostic marker in a tissue biopsy.

Astrocytomas have great variation in their presentation. The World Health Organization acknowledges the following grading system for astrocytomas:

Grade 1 - pilocytic astrocytoma - primarily pediatric tumor, with median age of diagnosis at 12

Grade 2 - diffuse astrocytoma

Grade 3 - anaplastic (malignant) astrocytoma

Grade 4 - glioblastoma multiforme (most common)

In addition to these four tumor grades, astrocytomas may combine with oligodendrocytes to produce oligoastrocytoma. Unique astrocytoma variants have also been known to exist.

PRND (prion-like protein doppel gene)

• the PRND gene might be a useful molecular marker in astrocytoma progression and in tumor grade definition. PMID: 15274317