PART TWO
Diagnostic Cytology
Fig. 24.9 Infectious mononucleosis. Heterogeneous lymphoid
population with marked reactive hyperplasia and immunoblasts (Diff-Quik
x OI).
Fig. 24.10 Cat scratch disease. Suppurative lymphadenitis with
neutrophils surrounding granulomas (Diff-Quik x MP).
Granulomatous Lymphadenitis
Granulomatous lymphadenitis is a form of chronic inflamma-
tion characterized by granulomas formed by syncytial aggregates
of epithelioid histiocytes with elongated nuclei, fine granular
chromatin, and small nucleoli in a background of lymphocytes
and occasionally plasma cells. There are generally two types
of granulomatous inflammation: foreign body and immune
granulomas. Foreign body granulomas are associated with inert
foreign material, while the immune granulomas are caused by
induction of a cell-mediated response to an insoluble particle
that gets engulfed by macrophages. T lymphocytes get activated
and cytokines such as interleukin-2 and interferon (IFN)-y,
which activate other T cells and macrophages, are produced.
IFN-y is the cytokine that transforms macrophages into epithe-
lioid and multinucleated giant cells.88 Multinucleated giant cells
consist of either the foreign body type (haphazardly arranged
nuclei) or the Langhans type (peripherally arranged nuclei).
On Papanicolaou-stained preparations, the epithelioid cells
tend to be spindly with wispy cytoplasm (Fig. 24.12). Granu-
lomatous inflammation is associated with a number of condi-
tions including infections (classically fungi and mycobacteria),
sarcoidosis, and foreign body and immune reactions. Certain
malignancies, such as HL and seminoma, may be associated
with a granulomatous inflammation, and a foreign body granu-
lomatous reaction to keratin may be seen in well-differentiated
squamous cell carcinoma.
Tuberculosis and leprosy are the mycobacterial infections that
may affect lymph nodes. The granulomatous inflammation of
tuberculous lymphadenitis is typically associated with necrotic
material, although sometimes the epithelioid granulomas are
without necrosis, particularly in the earlier stages of the infec-
tion. The term
caseous
necrosis is based on the gross appearance
of the necrotic material, which looks cheesy. At times liquefied
necrotic material with marked polymorphonuclear infiltration
gives rise to suppurative lymphadenitis. Sometimes the aspirates
may just contain the necrotic material without evidence of epi-
thelioid granuloma. The number of lymphoid cells and giant
cells is also variable. Various studies report wide differences
in positivity for acid-fast bacilli stained by the Ziehl-Neelsen
technique, with an average around 50% but ranging from 9 to
77%, with the greatest positivity occurring in suppurative lymph-
adenitis followed by caseous necrosis, and the least positivity in
cases of epithelioid granulomas without necrosis.58,89,90
The lepra bacilli of lepromatous leprosy are also acid-fast
organisms that stain with the modified Ziehl-Neelsen tech-
nique. The classic cell of leprosy is the syncytial histiocyte (Vir-
chow's cell or globus cell). These foamy, poorly circumscribed
cells are frequently multinucleated with multiple coarse mem-
brane-bound cytoplasmic vacuoles that tend to surround the
nuclei. In the aspirate, the membrane-bound vacuoles are some-
times found lying free in the background, presumably resulting
from rupture of histiocytes. The vacuoles are filled with numer-
ous lepra bacilli.91 A range of cytologic findings can be seen in
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