Grades I to IV
(World Health Organization) Astrocytic Tumors.
Panels A and B show circumscribed astrocytomas. Pilocytic astrocytomas (Panel A) are
typically indolent, have a limited invasive capacity, and rarely undergo anaplastic
progression. These tumors may have microvascular hyperplasia and cellular pleomorphism
despite their designation as grade I tumors. Pleomorphic xanthoastrocytomas (Panel B) are
also relatively circumscribed and, despite their distinct, conspicuous cellular
pleomorphism, tend to be low-grade (grade II) tumors with limited capacity for brain
invasion. Panels C through F show diffuse-type astrocytomas, which have the capacity for
dispersion into the surrounding brain and a high frequency of anaplastic progression. A
grade II astrocytoma (Panel C) is well-differentiated, with mild-to-moderate nuclear
pleomorphism. A grade III astrocytoma (Panel D) has a high rate of cell proliferation, as
indicated by the mitotic figures. These tumors commonly have a moderate degree of cellular
pleomorphism and more heterogeneous cellularity. Glioblastoma multiforme, grade IV, is the
most aggressive glial tumor and has the distinctive features of palisading or geographic
necrosis (Panel E) and conspicuous microvascular hyperplasia (Panel F) in addition to
marked cellular pleomorphism. (Tissue samples, stained with hematoxylin and eosin, |
