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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Artifacts<br />
A variety <strong>of</strong> artifacts can be identified in a bone marrow<br />
aspirate. They may be due to fixation, biopsy technique<br />
or due to specimen processing.<br />
EDTA: If a specimen is anticoagulated with EDTA<br />
<strong>and</strong> there is a delay in the preparation <strong>of</strong> smears,<br />
artifacts can appear in the cells. These can include the<br />
appearance <strong>of</strong> dyserythropoiesis with nuclear lobulation<br />
<strong>and</strong> fragmentation as well as cytoplasmic vacuoles.<br />
Neutrophils Necrobiosis (Degenerated Neutrophils):<br />
Neutrophil necrobiosis is a common phenomenon that<br />
can be seen both in normal individuals <strong>and</strong> in patients<br />
with a variety <strong>of</strong> medical conditions, including<br />
infections, inflammatory disorders, <strong>and</strong> malignancies.<br />
It is nondiagnostic <strong>and</strong> nonspecific. Degenerated<br />
neutrophils are generally easily identified because they<br />
resemble normal segmented neutrophils. They are round<br />
to oval cells ranging from 10 to 15 μm <strong>and</strong> their N:C<br />
ratio is 1:3 or less. The major distinguishing feature is that<br />
the nucleus shows karyorrhexis <strong>and</strong>/or pyknosis. These<br />
changes are appreciated when a cell with neutrophilic<br />
granules (pale pink cytoplasm with fine lilac granules)<br />
contains multiple, unconnected nuclear lobes<br />
(karyorrhexis) or a single, dark, round to oval nucleus<br />
(pyknosis). The chromatin is dense <strong>and</strong> homogeneous<br />
without visible parachromatin or nucleoli. The nuclear<br />
lobes may fragment into numerous small particles <strong>of</strong><br />
varying size that can resemble microorganisms such<br />
as bacteria or fungi. Also, the nuclear outlines may<br />
become indistinct <strong>and</strong> blurred. As the cellular<br />
degeneration continues, the cytoplasm will become<br />
hypogranulated, then agranular, <strong>and</strong> the cytoplasmic<br />
borders may become frayed <strong>and</strong> indistinct. Sometimes,<br />
the cells will contain scattered larger azurophilic or<br />
dark blue granules (toxic granulation). Vacuolation is<br />
frequent. If a cell is too degenerated to be recognized<br />
as a neutrophil <strong>and</strong> lacks recognizable cytoplasm, one<br />
should identify it as a basket/smudge cell. On occasion,<br />
necrobiotic neutrophils can contain ingested bacteria<br />
or fungi. However, the microscopist must be very careful<br />
when making this identification since nuclear fragments<br />
may appear similar <strong>and</strong> deceive the observer.<br />
Other cells that may resemble degenerated neutrophils<br />
are nucleated red cells in the blood <strong>and</strong> orthochromic<br />
normoblasts in the bone marrow. These cell types have<br />
pinkish orange, agranular cytoplasm <strong>and</strong> a single, <strong>of</strong>ten<br />
eccentric nucleus with dense chromatin <strong>and</strong> very little<br />
to no parachromatin.<br />
Specimen processing/suboptimal staining: If the slides<br />
are fixed before adequately drying, cellular outlines can<br />
Bone Marrow Cell Identification<br />
appear indistinct <strong>and</strong> the nucleus can appear to be<br />
leaking into the cytoplasm. Uptake <strong>of</strong> water in methanol<br />
when used in fixation can cause red blood cells to<br />
appear refractile with sharp round inclusions.<br />
Overstaining or understaining <strong>of</strong> aspirate smears can<br />
result in erroneous cell identification. Stain precipitate on<br />
the slides may be due to unclean slides or improper<br />
drying <strong>of</strong> the stained smears. Contaminated stain<br />
components may result in the presence <strong>of</strong> bacterial<br />
or fungal organisms in the smear but are typically<br />
extra cellular.<br />
Technique: If the aspirate specimen is partially clotted<br />
before smears are made, small clots can be mistaken<br />
for spicules <strong>and</strong> may lead to inaccurate assessment<br />
<strong>of</strong> cellularity or erroneous determination <strong>of</strong> absent iron<br />
stores with iron stains. Extensive platelet clumping can<br />
also mimic spicules <strong>and</strong> hinder cell distribution <strong>and</strong><br />
staining. Thick smears may result in poor staining <strong>of</strong><br />
cells <strong>and</strong> poor cytologic detail.<br />
Miscellaneous<br />
Blast Cell<br />
Squamous epithelial cells <strong>and</strong> endothelial cells are A<br />
blast is a large, round to oval cell, 10 to 20 μm in diameter.<br />
The nuclear-to-cytoplasmic ratio is high, approximately<br />
7:1 to 5:1. The blast <strong>of</strong>ten has a round to oval<br />
nucleus, but sometimes is indented or folded, <strong>and</strong> has<br />
fine, lacy, reticular chromatin. One or more prominent<br />
nucleoli may be seen. The cytoplasm is basophilic <strong>and</strong><br />
agranular.<br />
The morphologic features <strong>of</strong> a blast cell do not permit<br />
determination <strong>of</strong> the cell lineage. The one exception<br />
is the presence <strong>of</strong> Auer rods, which are diagnostic<br />
<strong>of</strong> myeloid lineage (i.e., myeloblast, see the entry for<br />
“Myeloblast with Auer rod”). Other cells that may have<br />
the appearance <strong>of</strong> a blast include lymphoblasts <strong>and</strong><br />
some lymphoma cells. In the absence <strong>of</strong> Auer rods,<br />
immunophenotyping by flow cytometry (or immunohistochemistry<br />
on tissue sections) or cytochemical staining<br />
(eg, peroxidase or Sudan black B reactivity) is required<br />
to determine the lineage <strong>of</strong> a given blast cell.<br />
Lymphoblasts are the most immature cells <strong>of</strong> the lymphoid<br />
series. They are most commonly seen in acute<br />
lymphoblastic leukemia (ALL) <strong>and</strong> lymphoid blast crisis<br />
<strong>of</strong> chronic myelogenous leukemia (CML). Lymphoblasts<br />
are widely variable in appearance, even at times within<br />
a single case, ranging from 10 to 20 μm in diameter with<br />
an N:C ratio ranging from 7:1 to 4:1. The broad<br />
morphologic spectrum <strong>of</strong> lymphoblasts permits their<br />
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