Diagnostic Cytology
Fig. 19.51 The pleural mesothelium has been replaced by a palisade of
macrophages, the classic histologic picture of rheumatoid pleuritis. Needle
biopsy specimen (H&E x LP). Reproduced with permission from Nosanchuk
JS, Naylor B: A unique cytologic picture in pleural fluid from patients with
rheumatoid arthritis.
Am J Clin Pathol
these two neoplasms are more likely to be a manifestation of
neoplastic change in B rather than T lymphocytes, enumera-
tion of the two types of lymphocytes in a lymphocytic effusion
might contribute to distinguishing between non-neoplastic and
neoplastic lymphocytic effusions. This approach has been used
with some success in making this discrimination.92,93 Most of
the cells in non-neoplastic lymphocytic effusions were T cells, in
contrast to the predominance of B cells in effusions of patients
with lymphoma or leukemia. The polymorphous nature of
a benign lymphocytic effusion can easily be established by
immunostaining for k and X light chains in cell blocks. A posi-
tive reaction for both light chains precludes the diagnosis of
The cytologic extremes of inflammation in serous effusions,
purulent and lymphocytic, are the exception. Effusions showing
any type of inflammatory component are more likely to show
a mixed, less monotonous picture of inflammation, one com-
posed of neutrophils, histiocytes, and lymphoid cells, includ-
ing plasma cells. In addition, various numbers of mesothelial
cells are likely to be present. In these mixed inflammatory effu-
sions, it is not possible to deduce the nature of the underlying
histopathologic process causing the effusion. Furthermore, one
cytologic picture of inflammation may become transformed into
another as a result of treatment or the natural course of events,
such as when an acute purulent inflammatory picture becomes
transformed into one of lymphocytic effusion.
Key features of non-neoplastic effusions
• Mesothelial cells stimulated to undergo hypertrophy;
• Strands of fibrin, which may cover mesothelial cells,
decreasing their number; and
• Inflammatory cells: types depend on inflammatory
stimulus and duration of effusion.
Specific inflammatory Pictures
Two specific inflammatory profiles, one of rheumatoid disease
and the other of systemic lupus erythematosus (SLE), may be
seen in serous effusions. The cytologic picture of SLE has been
reported in serous effusions from all three serous cavities,
Fig. 19.52 Rheumatoid pleuritis: an elongated, multinucleated histiocyte in
a background of amorphous granular material. Smear of pleural effusion
from the same patient as in Fig. 19.51 (Papanicolaou x MP). Reproduced with
permission from Nosanchuk JS, Naylor B: A unique cytologic picture in pleural
fluid from patients with rheumatoid arthritis.
Am J Clin Pathol
whereas that of rheumatoid serositis has been reported only in
pleural and pericardial effusions.94
Rheumatoid Disease
Rheumatoid disease acquires cytologic significance when the
necrotizing granulomatous inflammation found in the syn-
ovium and subsynovial tissue of rheumatoid arthritic joints
develops on the pleura or pericardium, resulting in effusion. A
cytologic picture may be seen in the effusions not only unique
but also pathognomonic of rheumatoid serositis, a picture
consisting of three elements: elongated spindle-shaped macro-
phages, multinucleated giant histiocytes, and necrotic granu-
lar background material.21,95 This triad is composed of cellular
elements exfoliated from areas of inflammation of the serous
membrane that are morphologic replicas of the necrotizing
granulomatous inflammatory reaction composed of a palisade
of elongated histiocytes that characterizes rheumatoid arthritis
and rheumatoid subcutaneous nodules.
Figure 19.51 illustrates a needle biopsy specimen of parietal
pleura of a woman with long-standing rheumatoid arthritis and
a pleural effusion of 6 months' duration. It depicts the typical
granulomatous inflammatory reaction of rheumatoid pleuritis,
consisting of a palisade of elongated histiocytes on the pleu-
ral surface. Such specimens may also contain multinucleated
giant histiocytes, a common manifestation of granulomatous
inflammatory reactions in general. The unique cytologic picture
of rheumatoid serositis in an effusion consists of viable and
necrotic cells exfoliated from such areas.
The number of elongated and giant multinucleated histiocytes
in rheumatoid effusions varies; they may be abundant, but
generally they are not, and occasionally they are absent. The
most striking examples of elongated histiocytes are up to about
150 pm in length and are fairly uniform in thickness except for
their tapering ends (Fig. 19.52).
Their cytoplasm is moderately dense, acidophilic or cyan-
ophilic (depending on the thickness of the smear and the
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