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594 PART 8 ■ Fundamentals of Hematological Analysis
Cell Count Lymphocytes
Erythrocyte and leukocyte counts are o limited value in the Lymphocytes resembling small peripheral blood lympho-
di erential diagnosis o pleural e usions. A massively bloody cytes are seen in variable numbers in most body f uids.
(hemorrhagic) e usion in the absence o trauma almost always However, lymphocytes may be variable in size and have an
suggests malignancy or occasionally pulmonary in arct. Pure immature appearance. T e cellular nucleus can be cleaved
blood in the pleural cavity, true hemothorax, results rom and exhibit nucleoli that are o en more prominent than
severe chest injuries. In these cases, a microhematocrit deter- those in peripheral blood lymphocytes.
mination will con rm that the microhematocrit value is simi- Degenerative changes in aged specimens can include vac-
lar to the patient’s peripheral blood packed RBC volume. uolization, pyknotic nuclear changes, and variations in the
Extremely elevated total leukocyte (WBC) counts o 50.0 × staining pattern. Arti actual changes can include a shrunken
9
10 /L or higher are consistent with a diagnosis o empyema. nucleus or dense clumps o very dark coloration, overall cell
9
In general, WBC counts less than 1.0 × 10 /L are associated shrinkage, and an irregular cytoplasmic border owing to
with transudates, and WBC counts greater than 1,000 × slow drying o the specimen on the slide.
10 /L are associated with exudates. E usions rom patients with tuberculosis or malignancies
9
Use undiluted f uid to per orm the cell count (re er to requently show a predominance o lymphocytes. E usions
the spinal f uid cell count procedure). Electronic counting rom patients with non-Hodgkin’s lymphoma can mani est
instruments should be used with caution, because debris malignant lymphocytes that are generally uni orm in compar-
may cause alsely increased counts. ison to benign conditions in which there is usually a mixture
o di erent types o lymphocytes (small, medium, and large).
Cell Differential Exam ination Detection o lymphocyte subsets ( and B lymphocytes)
Smears should be prepared or microscopic examination in pleural e usion may aid in the di erential diagnosis. T e
by cytocentri ugation, lter preparation (Millipore), or subset is considerably higher in f uids rom patients with pul-
sedimentation methods. Following preparation o the sedi- monary tuberculosis than in their blood. T e B subset is usually
ment, the smears should be properly stained with Wright’s or signi cantly lower in pleural f uid than in the circulating blood
Wright-Giemsa stain or di erential leukocyte evaluation or in patients with pulmonary tuberculosis, pulmonary malignant
stained with Papanicolaou’s stain or cytological evaluation. disorders, or nonspeci c pleuritis. T e presence o a monoclonal
Cell types that can be encountered in the examination o B-cell population is usually associated with malignant lymphoma.
a Wright-Giemsa–stained specimen include PMNs, eosino-
phils, basophils, lymphocytes, plasma cells, mononuclear Mononuclear Cells
phagocytes (monocytes, histiocytes, and macrophages), Mononuclear phagocytes (monocytes, histiocytes, and mac-
mesothelial cells (normal, reactive, atypical, and malignant), rophages) are seen in variable numbers in both benign and
and metastatic tumor (malignant) cells. In addition, in vivo malignant e usions. T e terms macrophage and histiocyte
LE cells have also been observed in pleural f uids. are used synonymously. Both monocytes and mesothelial
I a cytocentri uge is used or sediment preparation, arti- cells may be trans ormed into macrophages; the morpho-
acts may be encountered. Cells in the interior o a specimen logical distinction is not always obvious.
may be smaller in overall size with a denser nucleus than Macrophages vary in size, with a diameter ranging rom 15
cells at the periphery. Abnormal cells in particular are more to 25 µm. T e cytoplasm is pale gray and requently vacuolated.
likely to be a ected because o their propensity to be more Macrophages may contain phagocytized material such as RBC
ragile. In addition, nuclear-induced changes can include particles. T e nucleus is eccentrically located, with one or more
distorted shape and segmentation, ragmentation, or holes. observable nucleoli. Signet ring cells are a type o macrophage
Cytoplasmic arti acts can include irregular ragmentation, that orms when the small vacuoles o the cell use and orm
localization o granules, and peripheral vacuolization. one or two large vacuoles that push the nucleus against the side
PMNs should be distinguished rom mononuclear cells. It o the cell membrane. T e nucleus orms the stone compo-
can be di cult to di erentiate lymphocytes rom monocytes. nent o the ring. Signet ring macrophages with a normal-size
nucleus are commonly seen in sterile inf ammatory e usions.
Polymorphonuclear Segmented Neutrophils Te degeneration and death o a macrophage are charac-
PMNs in pleural f uid may appear morphologically identical to terized by an irregular nuclear shape and pyknosis, and cyto-
those in the circulating blood or may be di cult to recognize. plasmic vacuolization and inclusions, with peripheral raying.
Immature neutrophils are rarely seen except in chronic granu- T e number o mononuclear cells usually increases as an
locytic leukemia or a leukoerythroblastic condition. inf ammatory process becomes chronic. Mononuclear cells
In long-standing e usions, signs o cellular degeneration predominate in early inf ammatory e usions (e.g., pneu-
such as vacuolization and a decreased number o granules monia, pulmonary in arct, pancreatitis, and subphrenic
can occur in the cytoplasm. T e nuclei may appear as densely abscess). A er several days, macrophages, lymphocytes, and
stained spherical ragments and resemble nucleated erythro- mesothelial cells may predominate.
cytes (RBCs). Occasionally, the cytoplasm may have a bluish
color and resemble the cytoplasm o a lymphocyte. Eosinophils
An increase in PMNs ( able 29.7) is associated with exudates An increased number o eosinophils (eosinophilia) in pleu-
rom patients with in ectious diseases o a bacterial etiology. ral f uid is nonspeci c. Eosinophilia in pleural f uid (greater
