Hematology and Clinical Microscopy Glossary - College of American ...

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Cerebrospinal Fluid (CSF) and Body Fluid Cell Identification
inconspicuous nucleolus and light blue cytoplasm
containing numerous small azurophilic granules.
Lymphocyte, Reactive (Atypical)
All of the lymphocyte variants seen in peripheral blood
smears may be seen in body fluids. Reactive lymphocytes
tend to be larger with increases in volume of both
nuclei and cytoplasm. Most reactive lymphocytes in
viral illnesses type as T-lymphocytes. However,
plasmacytoid lymphocytes are also frequent.
Plasmacytoid lymphocytes are medium-sized cells
with irregular densely clumped nuclear chromatin,
absent to indistinct nucleoli, abundant basophilic
cytoplasm often with a paranuclear clear zone (hof).
Immunoblasts are large cells with round to oval nuclei,
fine delicate chromatin, prominent nucleoli and
moderate amounts of deeply basophilic cytoplasm.
The distinction between normal and reactive
lymphocytes is often difficult and subjective; however,
it is more important to distinguish reactive lymphocytes
from lymphoma cells. The reactive lymphocyte usually
has a distinct, smooth nuclear membrane in contrast
to the often irregular nuclear membrane of lymphoma
cells. Also in contrast to malignant lymphoproliferative
disorders, there is usually a spectrum of lymphocyte
morphology present in reactive conditions.
In some situations, differentiation of reactive from
malignant lymphocytes may require the use of
ancillary techniques including flow cytometry and
molecular analysis.
Lymphoma Cell
The morphology of lymphoma cells is dependent upon
the specific nature of the lymphoproliferative process.
Large cell lymphomas may be distinguished from
reactive lymphocytes by noting some or all of the
following features in lymphoma cells: high nuclear-tocytoplasmic
ratio; immature nuclear chromatin pattern;
irregular nucleus; prominent, large nucleoli; lack of a
clear Golgi region next to the nucleus; and monotonous
morphologic appearance. Lymphoma cells are usually
unaccompanied by other inflammatory cells.
Follicular lymphoma cells (formerly known as small
cleaved lymphoma cells) are slightly larger than normal
lymphocytes, and the nuclear-to-cytoplasmic ratio is
high; the nuclear chromatin pattern may appear dense
or hyperchromatic; and some of the nuclei may show
large clefts or irregularities in contour.
Lymphoblastic lymphoma cells appear similar to the
blasts described in the Miscellaneous Cells section
and sometimes contain a more folded or convoluted
nuclear pattern. With chronic lymphocytic leukemia or
small lymphocytic lymphoma, a uniform population of
small lymphocytes is present that often cannot be
distinguished morphologically from normal resting
lymphocytes. Sometimes, however, they are slightly
enlarged with prominent parachromatin clearing, and
occasional prolymphocytes may be present.
Prolymphocytes are large cells with clumped nuclear
chromatin, abundant basophilic cytoplasm, and a
characteristically prominent central nucleolus.
While lymphoma cells typically occur singly,
cytocentrifugation artifact may result in small cell
aggregates. Large clumps of tightly cohesive cells
with continuous outer borders are more characteristic
of carcinoma.
Immunocytochemical studies and flow cytometric
immunophenotypic studies are very useful in difficult
cases to distinguish malignant from reactive
lymphocytes, and lymphoma from nonhematopoietic
neoplasms.
Plasma Cell
Plasma cells are terminally differentiated forms of
reactive B-lymphocytes. Plasma cells can be seen in
body fluid but are not normally present. They may be
seen in infectious, inflammatory, or neoplastic processes.
They have round to oval, eccentrically placed nuclei
with condensed, clumped chromatin. The cytoplasm is
deeply basophilic, often with a paranuclear clear zone
or Golgi region. Occasionally, the cytoplasm may
contain immunoglobulin-filled vacuoles that may
appear clear. Binucleate plasma cells occasionally can
be seen. Mesothelial cells may resemble plasma cells,
but are usually larger in size, have more centrally placed
nuclei with smooth rather than ropey nuclear chromatin,
and usually lack the perinuclear clear zone.
Plasma Cell, Abnormal
Plasma cell neoplasms such as plasma cell myeloma
(multiple myeloma) are B-cell neoplasms. In most
situations, malignant plasma cells resemble normal
plasma cells, but also have prominent nucleoli,
irregularly shaped nuclei, more open chromatin, absent
perinuclear halo and high nuclear/cytoplasmic ratio.
Special studies such as immunophenotyping or
immunocytochemistry may be necessary to confirm
the monoclonal nature of the proliferation, indicating
malignancy.
College of American Pathologists 2012 Hematology, Clinical Microscopy, and Body Fluids Glossary