16
Central Nervous System
Fig. 16.17 Needle aspirate of oligodendroglioma is hypercellular, containing cells with round nuclei and wispy cytoplasm ((A) Papanicolaou x HP;
(B) immunoperoxidase using antibody against glial fibrillary acidic protein (GFAP) x HP).
Fig. 16.18 Needle aspirate of glioblastoma multiforme ((A) Papanicolaou x MP; (B) Immunoperoxidase using antibody against glial fibrillary acidic protein
(GFAP) x MP).
As shown in Table 16.2, when highly cellular, cytologically
malignant lesions are encountered, primary malignant brain
tumors, including glioblastoma multiforme, primary CNS
lymphoma, and primary sarcomas, should be considered in
addition to metastases from systemic carcinoma, lymphoma,
melanoma, and sarcoma. Cells from glioblastomas may range
from large to small and may exhibit pleomorphism. Nuclei are
typically hyperchromatic and irregular but generally lack the
pronounced clumping and clearing and macronucleoli char-
acteristic of metastatic carcinoma (Fig. 16.18). The cytoplasm
may be dense or wispy but generally lacks distinct cell borders,
and excentrically placed nuclei with cytoplasmic tails and pro-
cesses are common. In addition, most of these tumors con-
tain at least some cells that express GFAP, making this marker
useful in establishing the diagnosis of high-grade astrocytoma
(Fig. 16.18B). A limitation in most cytologic preparations,
however, is in distinguishing between anaplastic astrocytoma
(an astrocytic neoplasm of intermediate grade) and glioblas-
toma multiforme. Focal necrosis generally is the most reli-
able feature in separating glioblastoma from the lower grade
tumors in histologic sections of biopsy samples and cell blocks,
but it is usually difficult, if not impossible, to distinguish
necrosis from fibrin and other types of debris in needle aspi-
rates. Although the cytologic features of the neoplastic cells
in hypercellular aspirates may be sufficiently characteristic
to distinguish among glioblastoma, sarcoma metastasis, and
lymphoma, the application of an antibody panel, such as
that described in Table 16.1, can be used to make these
distinctions.
As shown in Table 16.3, many of the same neoplasms occur
in children as in adults. The distribution of astrocytic neo-
plasms is different, however, because the majority of childhood
gliomas occur in the posterior fossa, whereas they predominate
supratentorially in adults. Furthermore, brainstem gliomas are
one of the more common astrocytic tumors in childhood but
are rare after age 25. In addition to the tumors discussed thus
far, malignant small-cell neoplasms constitute a large propor-
tion of brain tumors in children. These neoplasms have been
termed primitive neuroectodermal tumors by some observ-
ers who note the morphologic similarities of these tumors in
various intracranial locations. Others retain the older termi-
nology that distinguishes medulloblastomas that occur in the
cerebellum from cerebral neuroblastomas and pineoblastomas.
In all locations, these tumors resemble adrenal neuroblastomas
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