Hematology and Clinical Microscopy Glossary - College of American ...
Hematology and Clinical Microscopy Glossary - College of American ...
Hematology and Clinical Microscopy Glossary - College of American ...
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Parabasal cells vary in size from 12 to 30 μm in diameter,<br />
about a quarter to half the size <strong>of</strong> superficial squamous<br />
cells. They tend to have a round to oval shape with<br />
smooth borders <strong>and</strong> occasional small vacuoles in the<br />
cytoplasm. They can appear in clusters <strong>and</strong> may be<br />
angulated <strong>and</strong> have irregular polygonal shapes.<br />
Their nuclei are round to oval <strong>and</strong> the nuclear- to-<br />
cytoplasmic ratio is higher than seen in superficial<br />
squamous cells.<br />
Basal cells are rarely seen in vaginal smears unless a<br />
pathologic process has damaged the squamous<br />
epithelium. These cells are smaller than parabasal cells<br />
<strong>and</strong> are round to oval in shape. They resemble very<br />
small parabasal cells. They have scanty cytoplasm<br />
<strong>and</strong> their nuclei are about the same size as those <strong>of</strong><br />
parabasal cells. However, due to their smaller size, basal<br />
cells have a higher nuclear-to-cytoplasmic ratio than<br />
parabasal cells.<br />
Squamous Epithelial Cell<br />
These large (30 to 50 μm) flat cells are derived from<br />
the lining <strong>of</strong> the female vagina <strong>and</strong> cervix. In wet<br />
preparation, squamous cells are about five to seven<br />
times as large as a red cell <strong>and</strong> larger than parabasal<br />
<strong>and</strong> basal cells. A single, small, condensed, round<br />
or oval central nucleus about the size <strong>of</strong> a small<br />
lymphocyte (10 to 12 μm) is seen in flat, round, or<br />
rectangular cells. There may be fine cytoplasmic<br />
granulation. The edges <strong>of</strong> the cell may be curled. The<br />
cell membrane is usually well-defined in brightfield <strong>and</strong><br />
phase microscopy. Degenerating squamous cells show<br />
granular swollen cytoplasm <strong>and</strong> eventual fraying; the<br />
nucleus becomes pyknotic <strong>and</strong> then lyses, <strong>and</strong> the cell<br />
may eventually resemble an amorphous disintegrating<br />
mass.<br />
Spermatozoa<br />
In wet preparations, the sperm head is about 4 to 6 μm<br />
long, usually tapering anteriorly. It is smaller <strong>and</strong><br />
narrower than red cells. Slender tails are about 40 to<br />
60 μm long. The head may be separated from the tail,<br />
making identification more difficult.<br />
Fern Test<br />
Evaluation <strong>of</strong> an air-dried slide prepared from the<br />
vaginal pool is one <strong>of</strong> the most widely used tests to<br />
detect rupture <strong>of</strong> the amniotic membranes <strong>and</strong> the<br />
early onset <strong>of</strong> labor. When properly performed <strong>and</strong>,<br />
particularly if used in conjunction with another widely<br />
used test such as the nitrazine test, this is highly sensitive<br />
<strong>and</strong> specific for the detection <strong>of</strong> ruptured membranes.<br />
<strong>Clinical</strong> <strong>Microscopy</strong> Miscellaneous Cell<br />
The “fern test” was initially described in 1955 <strong>and</strong> its ease<br />
<strong>of</strong> use <strong>and</strong> clinical utility has been confirmed by multiple<br />
published studies.<br />
A sample <strong>of</strong> fluid is collected from the vaginal pool <strong>and</strong><br />
allowed to air dry on a microscope slide for five to seven<br />
minutes. This is then examined under the microscope<br />
at low power. A positive test, indicating the presence<br />
<strong>of</strong> amniotic fluid, consists <strong>of</strong> an elaborate arborized<br />
crystallization pattern (ferning) best visualized when<br />
the substage condensor is lowered to accentuate the<br />
diffraction pattern. The test may be positive as early as<br />
12 weeks <strong>of</strong> gestation. Common contaminants such as<br />
blood, urine, meconium (by itself indicative <strong>of</strong> ruptured<br />
membranes), semen, or alkaline antiseptic solutions<br />
that may be present in the vagina do not usually cause<br />
a falsely negative result unless present in very high<br />
concentrations. Inadvertent contamination <strong>of</strong> the<br />
specimen by cervical mucus may cause a falsely<br />
positive result but the arborization pattern is less<br />
elaborate <strong>and</strong> normally will not form after the first<br />
trimester <strong>of</strong> pregnancy due to high levels <strong>of</strong><br />
progesterone present.<br />
Organisms<br />
Trichomonas<br />
Trichomonas vaginalis primarily causes vaginal infection,<br />
but also is capable <strong>of</strong> infecting the urethra, periurethral<br />
gl<strong>and</strong>s, bladder, <strong>and</strong> prostate. The normal habitat <strong>of</strong><br />
T. vaginalis is the vagina in women <strong>and</strong> the prostate<br />
in men. In women, the organism feeds on the<br />
mucosal surface <strong>of</strong> the vagina, ingesting bacteria <strong>and</strong><br />
leukocytes.<br />
T. vaginalis is a protozoan flagellate with only a<br />
trophozoite stage. It is pyriform or pear-shaped with<br />
a length <strong>of</strong> 7 to 23 μm. There is a single nucleus <strong>and</strong> a<br />
stout central axostyle protruding from the posterior end<br />
<strong>of</strong> the body. Additional morphologic features include<br />
four anterior flagella <strong>and</strong> an undulating membrane in<br />
the anterior half from which projects a single posterior<br />
flagellum. In wet mounts, it demonstrates a jerky,<br />
rotating, nondirectional leaf-like motion. Rippling <strong>of</strong> the<br />
undulating membrane can be seen for several hours<br />
after cessation <strong>of</strong> organism motility.<br />
Yeast/Fungi<br />
C<strong>and</strong>ida albicans is a colorless, ovoid, 5 to 7 μm,<br />
thick-walled cell. A cell with a single bud is<br />
characteristic. The cells stain poorly with aqueous stains<br />
in wet preparations, but are strongly positive with Gram<br />
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