Diagnostic Cytology
Fig. 7.68 (A)
T ric h o m o n a s v a g in a lis
infection revealing "BB shot" or "cannonball" appearance (LBGS x LP). (B)
Trichom onas
attached to the surface of
squamous cells (LBGS x MP).
Fig. 7.69
T ric h o m o n a s v a g in a lis
attached to the edges of the squamous
epithelial cell in the center of the field (LBGS Papanicolaou x MP).
changes as in pregnancy or late luteal phase, and atrophic cellu-
lar changes all may make the detection of
T. vaginalis
difficult. In
cytologic preparations from asymptomatic women, the organ-
isms are best detected by examining cervical material obtained
by endocervical canal scraping or aspiration.
In well-stained and representative vaginopancervical smears,
T. vaginalis
can be suspected by the presence of a number of fea-
tures. These include the occurrence of aggregates of leukocytes
covering the surfaces of the isolated, mature squamous epithe-
lial cells (Fig. 7.68). These leukocytic agglomerations have been
called "BB shots" and "cannonballs" and represent a number
T. vaginalis
organisms feeding on the squamous epithelial
cell that, in turn, is phagocytosed by the leukocytes and mac-
rophages. The attachment of
T. vaginalis
to the margins of the
squamous epithelial cells can be easily studied by appropriate
immunoenzymatic techniques (Fig. 7.69). Similar changes to a
lesser degree can be observed in the LBGS also.
T. vaginalis
may be suspected by observing
in the vaginal smears. These are large, generally non-
branching, curved bacillary structures distinct from lactobacilli
and were described in detail earlier. Bibbo and Wied observed
together in 95% of more than 1000
cases examined.13
In women having a total hysterectomy,
T. vaginalis
most often without the accompanying inflammatory reaction.
In such smears, numerous mature squamous cells and
T. vagi-
organisms occur with minimal changes, and only some
bacteria may occur as accompaniments.
T. vaginalis
frequently appears as small,
round or oval structures. Their size may vary from that of the
nucleus of a leukocyte to that of the parabasal cell. Extremely
large, giant forms of
150-200 nm in size, have
been observed. The organisms stain a cytoplasmic color that
may vary according to the pH of the vagina, staining quality, and
fixation. Generally, they are cyanophilic or delicate lavender in
color. Bizarre, elongated, or tadpole forms may occur (Fig. 7.70).
Although they frequently occur singly, in cases of severe infection
and immunosuppression, large microcolonies of the organisms
may appear in the smear. The organisms always have a distinct,
faint, vesicular nucleus. Most often it is eccentric. Sometimes a
number of acidophilic, uniformly sized granules may be observed
within the organisms.
Trichomonas vaginalis
multiplies by binary
fission, and the organisms may be observed in mitosis.125a,125b
Key features of
Trichom onas vaginalis
• May be suspected by "BB Shots" (tight clusters of
neutrophils) and leptothrix;
• Inflammatory reaction absent after total hysterectomy;
• Variable size, shape, and color;
• Must have faint, vesicular nucleus for diagnosis; and
• Presence of flagella—better seen in LBGS.
Morphology is better recognized in LBGS-based preparations;
flagella and pear-shaped forms as seen in the living organisms
may be recognizable. A specificity of 93%, with a sensitivity of
50%, a positive predictive value of 77%, and a negative predic-
tive value of 80% for the detection of
T. vaginalis
were obtained
in an evaluation of LBGS-based specimens when compared to
the wet-mount and culture studies.125b
Some correlation has been observed between the size of the
T. vaginalis
and their pathogenicity. It is believed that the smaller
organisms cause more fulminant and symptomatic infection.
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