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590 PART 8 ■ Fundamentals of Hematological Analysis
evident in a specimen that is a ew hours old. Vacuolization o unless accompanied by clinical symptoms, the demonstra-
PMNs may be noted in abnormal or old specimens. tion o a number o leukemic cells is strongly suggestive o
T e overall size o PMNs may be enlarged i the cell is in the involvement o the subarachnoid space in patients with leu-
process o phagocytosis. T e nucleus may be hyperlobulated kemia or lymphoma.
with long and narrow laments. Older neutrophils can exhibit
pyknosis or karyorrhexis (one or more spherical, densely stain- Malignant Cells
ing nuclear ragments) and be mistaken or nucleated RBCs. T e presence o even a ew cells with malignant eatures is diag-
T e observation o more than an occasional PMN in the nostic o metastatic involvement o the subarachnoid space.
CSF classically suggests bacterial in ection. However, an T ese cells may also originate rom primary tumors o the
increase in the number o PMNs can be caused by in ectious brain or spinal cord. Approximately 29% o primary tumors o
and nonin ectious agents. In ectious disorders with a pre- the CNS shed identi able malignant cells into the CSF.
dominance o PMNs include acute, untreated bacterial men- Malignant cells are recognizable by the dyssynchrony in
ingitis; viral meningoencephalitis during the rst ew days maturation between cells. In addition, malignant cells occur
o the in ection; early tuberculosis; and mycotic meningitis. singly or in clusters. Malignant cells are usually accompanied
Aseptic meningitis can exist in cases in which the septic ocus by many histiocytes.
is adjacent to the meninges. Nonin ectious causes o increased Medulloblastoma, a highly malignant tumor, o en
PMN numbers include a reaction to CNS hemorrhage (3 to 4 invades the subarachnoid space and sheds cells into the
days a erward), injection o oreign substances such as lido- CSF. T e cells o medulloblastoma are small and hyper-
caine into the subarachnoid space, and leukemic in ltration. chromatic. T ey can occur singly, in rosette ormations, or
in clumps. T ese malignant cells are very similar in appear-
Other Granulocytic Cells ance to neuroblastoma, retinoblastoma, and oat cell carci-
Eosinophils and basophils are not normally seen in the CSF. noma cells.
T eir appearance in CSF is similar to that in peripheral blood. Cells Unique to the Cerebrospinal Fluid
Eosinophils may be increased owing to causes similar
to those o an increase in PMNs (e.g., bacterial in ection). Ependymal Cells
However, unique causes o an increase in eosinophils include A ew ependymal cells, the cuboidal epithelial cells that cover
systemic parasitic or ungal in ections, systemic drug reac- the sur ace o the cerebral ventricles and the choroid plexus,
tion, and idiopathic eosinophilic meningitis. may be seen in normal CSF. T ese cells become rounded in
Increased basophil numbers can be observed in chronic appearance a er separating rom the lining and resemble lym-
basophilic leukemia, which involves the meninges; chronic phocytes or monocytoid cells. Ependymal cells are medium
granulocytic leukemia; purulent meningitis; inf ammatory in size and may appear in clusters or as individual cells. T e
processes; and parasitic in ections. nucleus is round and generally in the center o the cell. T e
chromatin is dense and may be slightly grainy or pyknotic. In
Plasm a Cells addition, nucleoli may be seen. T e nuclear-cytoplasmic ratio
Plasma cells are normally absent in the CSF. T ey may be is 1:2 to 1:3. Cellular cytoplasm is usually abundant and stains
ound in association with viral disorders such as herpes sim- a cloudy gray-blue or pinkish color with Wright-Giemsa stain.
plex virus in ection, meningoencephalitis, syphilitic involve- Te cytoplasm displays inde nite borders, and ragmented
ment o the CNS, and Hodgkin’s disease as well as a er a projections o cytoplasm or pseudopods may be seen.
subarachnoid hemorrhage. Although ependymal cells appear similar to choroidal
cells on light microscopy, they di er rom choroidal epithe-
Erythrocytes lial cells because o the absence o intracytoplasm inclusions
A ew erythrocytes (RBCs) may be seen. An increased con- and the border o cilia extending into the ventricular cavity.
centration o RBCs may be seen in traumatic tap specimens An increased number o ependymal cells in the CSF is
or in CSF rom patients who have conditions such as a bleed- rare. However, they may be observed in specimens rom
ing subarachnoid hemorrhage or intracerebral hemorrhage young children and in patients with hydrocephalus, or ol-
(see the discussion o gross examination). T e number o lowing pneumoencephalography. Finding these cells in the
RBCs may also be increased in chronic myelogenous leuke- CSF is o limited diagnostic value.
mia or leukoerythroblastic conditions.
Choroidal Cells
Mesothelial Cells Choroidal cells are medium in size (about the size o a mature
Mesothelial cells are not ound in normal CSF. I seen, they can lymphocyte) and usually occur in a clump o similar cells.
resemble pia arachnoidal or ependymal cells. Both monocytes T e nucleus is round or cuboidal and eccentrically located. It
and mesothelial cells may be trans ormed into macrophages, has a loose chromatin structure and nucleoli are not visible.
and the morphological distinction is not always obvious. A generous amount o cytoplasm is evident and is gray or
slightly basophilic.
Im m ature Cells T e nucleus changes rom a blue to pink-tinted color in
Immature cells can be seen in patients with leukemias or older samples. In addition, peripheral vacuolization in the
malignant lymphomas. Although a single blast is insigni cant cytoplasm can be observed in an aging specimen.
