Cytology of Other Body Sites
Central Nervous System
Sandra H Bigner and Alicia L Carter
In tro d u c tio n
R e a c tio n s to In tra v e n tric u la r S h u n ts
P re p a ra to ry M e th o d s
N e o p la sia
C e r e b r o s p in a l F lu id
L e u k e m ia
F in e - N e e d le A s p ir a t io n B io p s y
L y m p h o m a
N o rm a l C e re b ro s p in a l F lu id a n d H is to lo g y
M e t a s t a t ic C a r c in o m a a n d M e n in g e a l C a r c in o m a to s is
V e n tric u la r F lu id
P r im a r y C e n tr a l N e rv o u s S y s te m T u m o r s
In fe c tio u s C o n d itio n s
D e m y e lin a t in g D ise a s e s
V a s c u la r D iso rd e rs
T ra u m a
Although cerebrospinal fluid (CSF) is often discussed as one of
the body cavity fluids, several major differences exist between
this fluid and effusions. First, CSF is a fluid that is normally
present, whereas an effusion is always a pathologic finding. Sec-
ond, the pial and arachnoidal cells that line the subarachnoid
space (SAS) rarely shed into the CSF, whereas the mesothelial
cells that line the pleural, peritoneal, and pericardial cavities fre-
quently proliferate and are often major cellular components of
effusions. Third, because the presence of an effusion is abnor-
mal, cytologic evaluation of this fluid is most often performed
to determine whether the accumulation has a neoplastic etiol-
ogy. Sampling of CSF, in contrast, is performed in various clini-
cal situations. For example, examination of this fluid is among
the most direct and effective means of diagnosing conditions
that primarily involve the SAS, such as leptomeningitis, sub-
arachnoid hemorrhage, and meningeal carcinomatosis. In addi-
tion, because of the contact of the SAS with the entire brain and
spinal cord as well as its continuity with the ventricular system,
CSF often indirectly reflects disorders located primarily within
the parenchyma of the central nervous system (CNS). Therefore,
cytologic evaluation of a sample of CSF requires knowledge of
the clinical findings of the patient from whom it was obtained.
An understanding of the cytologic presentation of the spec-
trum of CNS disorders, which can be manifested in CSF, is also
Fine-needle aspiration of the brain, like fine-needle aspiration
of other body sites, is generally performed as one step in the
evaluation of mass lesions. As in other locations, the differential
diagnosis includes inflammatory masses, such as abscesses,
tuberculomas and other types of granulomas, and neoplasms,
such as lymphomas, metastatic tumors, and primary brain
The application of cytologic techniques to diagnoses of con-
ditions manifested in CSF are discussed here with emphasis on
disorders that occur primarily in the SAS. The presentation of
intracranial lesions in needle aspirates and cyst fluids is also
described, including the cytologic characteristics of the most
common types of primary brain tumors.
Preparatory Methods
Cerebrospinal Fluid
Because of the low cellularity of CSF, cytopreparatory meth-
ods have been developed to allow concentration of the cells
with preservation of their morphologic characteristics. The two
methods most widely used today are membrane filtration and
cytocentrifugation. Some laboratories have begun to apply thin-
preparation techniques to samples of CSF.1
However, a rigorous
analysis of this method including a case-by-case comparison
with the more traditional methods has not been carried out to
The types of membranes used in preparations of CSF are
Millipore filters, nucleopore filters, and Gelman filters. Filters
have the advantage, when used correctly, of retention of virtu-
ally every cell in the sample. One disadvantage is that staining
with methods other than the Papanicolaou stain is generally
not satisfactory. In addition, good results require considerable
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